What changed?

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: ['postgres', 'postgres_verbose', 'sql_standard', 'iso_8601']
 
-Sets the display format for interval values. The value sql_standard will produce output matching SQL standard interval literals. The value postgres (which is the default) will produce output matching PostgreSQL releases prior to 8.4 when the DateStyle parameter was set to ISO. The value postgres_verbose will produce output matching PostgreSQL releases prior to 8.4 when the DateStyle parameter was set to non-ISO output. The value iso_8601 will produce output matching the time interval "format with designators" defined in section 4.4.3.2 of ISO 8601. The IntervalStyle parameter also affects the interpretation of ambiguous interval input. See Section 8.5.4 for more information.
+Sets the display format for interval values. The value sql_standard will produce output matching SQL standard interval literals. The value postgres (which is the default) will produce output matching PostgreSQL releases prior to 8.4 when the DateStyle parameter was set to ISO. The value postgres_verbose will produce output matching PostgreSQL releases prior to 8.4 when the DateStyle parameter was set to non-ISO output. The value iso_8601 will produce output matching the time interval “format with designators” defined in section 4.4.3.2 of ISO 8601. The IntervalStyle parameter also affects the interpretation of ambiguous interval input. See Section 8.5.4 for more information.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: bool
+context: superuser
+boot_val: off
+unit: None
+enumvals: None
+
+Allows tablespaces to be created as directories inside pg_tblspc, when an empty location string is provided to the CREATE TABLESPACE command. This is intended to allow testing replication scenarios where primary and standby servers are running on the same machine. Such directories are likely to confuse backup tools that expect to find only symbolic links in that location. Only superusers can change this setting.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: s
 enumvals: None
 
-The archive_command is only invoked for completed WAL segments. Hence, if your server generates little WAL traffic (or has slack periods where it does so), there could be a long delay between the completion of a transaction and its safe recording in archive storage. To limit how old unarchived data can be, you can set archive_timeout to force the server to switch to a new WAL segment file periodically. When this parameter is greater than zero, the server will switch to a new segment file whenever this many seconds have elapsed since the last segment file switch, and there has been any database activity, including a single checkpoint. (Increasing checkpoint_timeout will reduce unnecessary checkpoints on an idle system.) Note that archived files that are closed early due to a forced switch are still the same length as completely full files. Therefore, it is unwise to use a very short archive_timeout — it will bloat your archive storage. archive_timeout settings of a minute or so are usually reasonable. You should consider using streaming replication, instead of archiving, if you want data to be copied off the master server more quickly than that. This parameter can only be set in the postgresql.conf file or on the server command line.
+The archive_command is only invoked for completed WAL segments. Hence, if your server generates little WAL traffic (or has slack periods where it does so), there could be a long delay between the completion of a transaction and its safe recording in archive storage. To limit how old unarchived data can be, you can set archive_timeout to force the server to switch to a new WAL segment file periodically. When this parameter is greater than zero, the server will switch to a new segment file whenever this many seconds have elapsed since the last segment file switch, and there has been any database activity, including a single checkpoint (checkpoints are skipped if there is no database activity). Note that archived files that are closed early due to a forced switch are still the same length as completely full files. Therefore, it is unwise to use a very short archive_timeout — it will bloat your archive storage. archive_timeout settings of a minute or so are usually reasonable. You should consider using streaming replication, instead of archiving, if you want data to be copied off the master server more quickly than that. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-This controls whether the array input parser recognizes unquoted NULL as specifying a null array element. By default, this is on, allowing array values containing null values to be entered. However, PostgreSQL versions before 8.2 did not support null values in arrays, and therefore would treat NULL as specifying a normal array element with the string value "NULL". For backward compatibility with applications that require the old behavior, this variable can be turned off. Note that it is possible to create array values containing null values even when this variable is off.
+This controls whether the array input parser recognizes unquoted NULL as specifying a null array element. By default, this is on, allowing array values containing null values to be entered. However, PostgreSQL versions before 8.2 did not support null values in arrays, and therefore would treat NULL as specifying a normal array element with the string value “NULL”. For backward compatibility with applications that require the old behavior, this variable can be turned off. Note that it is possible to create array values containing null values even when this variable is off.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Specifies the maximum age (in transactions) that a table's pg_class.relfrozenxid field can attain before a VACUUM operation is forced to prevent transaction ID wraparound within the table. Note that the system will launch autovacuum processes to prevent wraparound even when autovacuum is otherwise disabled. Vacuum also allows removal of old files from the pg_clog subdirectory, which is why the default is a relatively low 200 million transactions. This parameter can only be set at server start, but the setting can be reduced for individual tables by changing table storage parameters. For more information see Section 24.1.5.
+Specifies the maximum age (in transactions) that a table's pg_class.relfrozenxid field can attain before a VACUUM operation is forced to prevent transaction ID wraparound within the table. Note that the system will launch autovacuum processes to prevent wraparound even when autovacuum is otherwise disabled. Vacuum also allows removal of old files from the pg_xact subdirectory, which is why the default is a relatively low 200 million transactions. This parameter can only be set at server start, but the setting can be reduced for individual tables by changing table storage parameters. For more information see Section 24.1.5.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: 8kB
 enumvals: None
 
-Whenever more than bgwriter_flush_after bytes have been written by the bgwriter, attempt to force the OS to issue these writes to the underlying storage. Doing so will limit the amount of dirty data in the kernel's page cache, reducing the likelihood of stalls when an fsync is issued at the end of a checkpoint, or when the OS writes data back in larger batches in the background. Often that will result in greatly reduced transaction latency, but there also are some cases, especially with workloads that are bigger than shared_buffers, but smaller than the OS's page cache, where performance might degrade. This setting may have no effect on some platforms. The valid range is between 0, which disables forced writeback, and 2MB. The default is 512kB on Linux, 0 elsewhere. (If BLCKSZ is not 8kB, the default and maximum values scale proportionally to it.) This parameter can only be set in the postgresql.conf file or on the server command line.
+Whenever more than bgwriter_flush_after bytes have been written by the background writer, attempt to force the OS to issue these writes to the underlying storage. Doing so will limit the amount of dirty data in the kernel's page cache, reducing the likelihood of stalls when an fsync is issued at the end of a checkpoint, or when the OS writes data back in larger batches in the background. Often that will result in greatly reduced transaction latency, but there also are some cases, especially with workloads that are bigger than shared_buffers, but smaller than the OS's page cache, where performance might degrade. This setting may have no effect on some platforms. The valid range is between 0, which disables forced writeback, and 2MB. The default is 512kB on Linux, 0 elsewhere. (If BLCKSZ is not 8kB, the default and maximum values scale proportionally to it.) This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-The number of dirty buffers written in each round is based on the number of new buffers that have been needed by server processes during recent rounds. The average recent need is multiplied by bgwriter_lru_multiplier to arrive at an estimate of the number of buffers that will be needed during the next round. Dirty buffers are written until there are that many clean, reusable buffers available. (However, no more than bgwriter_lru_maxpages buffers will be written per round.) Thus, a setting of 1.0 represents a "just in time" policy of writing exactly the number of buffers predicted to be needed. Larger values provide some cushion against spikes in demand, while smaller values intentionally leave writes to be done by server processes. The default is 2.0. This parameter can only be set in the postgresql.conf file or on the server command line.
+The number of dirty buffers written in each round is based on the number of new buffers that have been needed by server processes during recent rounds. The average recent need is multiplied by bgwriter_lru_multiplier to arrive at an estimate of the number of buffers that will be needed during the next round. Dirty buffers are written until there are that many clean, reusable buffers available. (However, no more than bgwriter_lru_maxpages buffers will be written per round.) Thus, a setting of 1.0 represents a “just in time” policy of writing exactly the number of buffers predicted to be needed. Larger values provide some cushion against spikes in demand, while smaller values intentionally leave writes to be done by server processes. The default is 2.0. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Sets the planner's estimate of the fraction of a cursor's rows that will be retrieved. The default is 0.1. Smaller values of this setting bias the planner towards using "fast start" plans for cursors, which will retrieve the first few rows quickly while perhaps taking a long time to fetch all rows. Larger values put more emphasis on the total estimated time. At the maximum setting of 1.0, cursors are planned exactly like regular queries, considering only the total estimated time and not how soon the first rows might be delivered.
+Sets the planner's estimate of the fraction of a cursor's rows that will be retrieved. The default is 0.1. Smaller values of this setting bias the planner towards using “fast start” plans for cursors, which will retrieve the first few rows quickly while perhaps taking a long time to fetch all rows. Larger values put more emphasis on the total estimated time. At the maximum setting of 1.0, cursors are planned exactly like regular queries, considering only the total estimated time and not how soon the first rows might be delivered.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-This parameter enables per-database user names. It is off by default. This parameter can only be set in the postgresql.conf file or on the server command line. If this is on, you should create users as username@dbname. When username is passed by a connecting client, @ and the database name are appended to the user name and that database-specific user name is looked up by the server. Note that when you create users with names containing @ within the SQL environment, you will need to quote the user name. With this parameter enabled, you can still create ordinary global users. Simply append @ when specifying the user name in the client, e.g., joe@. The @ will be stripped off before the user name is looked up by the server. db_user_namespace causes the client's and server's user name representation to differ. Authentication checks are always done with the server's user name so authentication methods must be configured for the server's user name, not the client's. Because md5 uses the user name as salt on both the client and server, md5 cannot be used with db_user_namespace. Note: This feature is intended as a temporary measure until a complete solution is found. At that time, this option will be removed.
+This parameter enables per-database user names. It is off by default. This parameter can only be set in the postgresql.conf file or on the server command line. If this is on, you should create users as username@dbname. When username is passed by a connecting client, @ and the database name are appended to the user name and that database-specific user name is looked up by the server. Note that when you create users with names containing @ within the SQL environment, you will need to quote the user name. With this parameter enabled, you can still create ordinary global users. Simply append @ when specifying the user name in the client, e.g., joe@. The @ will be stripped off before the user name is looked up by the server. db_user_namespace causes the client's and server's user name representation to differ. Authentication checks are always done with the server's user name so authentication methods must be configured for the server's user name, not the client's. Because md5 uses the user name as salt on both the client and server, md5 cannot be used with db_user_namespace. Note This feature is intended as a temporary measure until a complete solution is found. At that time, this option will be removed.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-When set, debug_pretty_print indents the messages produced by debug_print_parse, debug_print_rewritten, or debug_print_plan. This results in more readable but much longer output than the "compact" format used when it is off. It is on by default.
+When set, debug_pretty_print indents the messages produced by debug_print_parse, debug_print_rewritten, or debug_print_plan. This results in more readable but much longer output than the “compact” format used when it is off. It is on by default.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: ['serializable', 'repeatable read', 'read committed', 'read uncommitted']
 
-Each SQL transaction has an isolation level, which can be either "read uncommitted", "read committed", "repeatable read", or "serializable". This parameter controls the default isolation level of each new transaction. The default is "read committed". Consult Chapter 13 and SET TRANSACTION for more information.
+Each SQL transaction has an isolation level, which can be either “read uncommitted”, “read committed”, “repeatable read”, or “serializable”. This parameter controls the default isolation level of each new transaction. The default is “read committed”. Consult Chapter 13 and SET TRANSACTION for more information.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: bool
+context: user
+boot_val: on
+unit: None
+enumvals: None
+
+Enables or disables the query planner's use of gather merge plan types. The default is on.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Soft upper limit of the size of the set returned by GIN index scans. For more information see Section 63.5.
+Soft upper limit of the size of the set returned by GIN index scans. For more information see Section 64.5.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: kB
 enumvals: None
 
-Sets the maximum size of the GIN pending list which is used when fastupdate is enabled. If the list grows larger than this maximum size, it is cleaned up by moving the entries in it to the main GIN data structure in bulk. The default is four megabytes (4MB). This setting can be overridden for individual GIN indexes by changing index storage parameters. See Section 63.4.1 and Section 63.5 for more information.
+Sets the maximum size of the GIN pending list which is used when fastupdate is enabled. If the list grows larger than this maximum size, it is cleaned up by moving the entries in it to the main GIN data structure in bulk. The default is four megabytes (4MB). This setting can be overridden for individual GIN indexes by changing index storage parameters. See Section 64.4.1 and Section 64.5 for more information.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: bool
 context: postmaster
-boot_val: off
+boot_val: on
 unit: None
 enumvals: None
 
-Specifies whether or not you can connect and run queries during recovery, as described in Section 26.5. The default value is off. This parameter can only be set at server start. It only has effect during archive recovery or in standby mode.
+Specifies whether or not you can connect and run queries during recovery, as described in Section 26.5. The default value is on. This parameter can only be set at server start. It only has effect during archive recovery or in standby mode.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Reports whether PostgreSQL was built with support for 64-bit-integer dates and times. This can be disabled by configuring with --disable-integer-datetimes when building PostgreSQL. The default value is on.
+Reports whether PostgreSQL was built with support for 64-bit-integer dates and times. As of PostgreSQL 10, this is always on.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Specifies the TCP/IP address(es) on which the server is to listen for connections from client applications. The value takes the form of a comma-separated list of host names and/or numeric IP addresses. The special entry * corresponds to all available IP interfaces. The entry 0.0.0.0 allows listening for all IPv4 addresses and :: allows listening for all IPv6 addresses. If the list is empty, the server does not listen on any IP interface at all, in which case only Unix-domain sockets can be used to connect to it. The default value is localhost, which allows only local TCP/IP "loopback" connections to be made. While client authentication (Chapter 20) allows fine-grained control over who can access the server, listen_addresses controls which interfaces accept connection attempts, which can help prevent repeated malicious connection requests on insecure network interfaces. This parameter can only be set at server start.
+Specifies the TCP/IP address(es) on which the server is to listen for connections from client applications. The value takes the form of a comma-separated list of host names and/or numeric IP addresses. The special entry * corresponds to all available IP interfaces. The entry 0.0.0.0 allows listening for all IPv4 addresses and :: allows listening for all IPv6 addresses. If the list is empty, the server does not listen on any IP interface at all, in which case only Unix-domain sockets can be used to connect to it. The default value is localhost, which allows only local TCP/IP “loopback” connections to be made. While client authentication (Chapter 20) allows fine-grained control over who can access the server, listen_addresses controls which interfaces accept connection attempts, which can help prevent repeated malicious connection requests on insecure network interfaces. This parameter can only be set at server start.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-This variable specifies one or more shared libraries that are to be preloaded at connection start. The parameter value only takes effect at the start of the connection. Subsequent changes have no effect. If a specified library is not found, the connection attempt will fail. This option can be set by any user. Because of that, the libraries that can be loaded are restricted to those appearing in the plugins subdirectory of the installation's standard library directory. (It is the database administrator's responsibility to ensure that only "safe" libraries are installed there.) Entries in local_preload_libraries can specify this directory explicitly, for example $libdir/plugins/mylib, or just specify the library name — mylib would have the same effect as $libdir/plugins/mylib. The intent of this feature is to allow unprivileged users to load debugging or performance-measurement libraries into specific sessions without requiring an explicit LOAD command. To that end, it would be typical to set this parameter using the PGOPTIONS environment variable on the client or by using ALTER ROLE SET. However, unless a module is specifically designed to be used in this way by non-superusers, this is usually not the right setting to use. Look at session_preload_libraries instead.
+This variable specifies one or more shared libraries that are to be preloaded at connection start. It contains a comma-separated list of library names, where each name is interpreted as for the LOAD command. Whitespace between entries is ignored; surround a library name with double quotes if you need to include whitespace or commas in the name. The parameter value only takes effect at the start of the connection. Subsequent changes have no effect. If a specified library is not found, the connection attempt will fail. This option can be set by any user. Because of that, the libraries that can be loaded are restricted to those appearing in the plugins subdirectory of the installation's standard library directory. (It is the database administrator's responsibility to ensure that only “safe” libraries are installed there.) Entries in local_preload_libraries can specify this directory explicitly, for example $libdir/plugins/mylib, or just specify the library name — mylib would have the same effect as $libdir/plugins/mylib. The intent of this feature is to allow unprivileged users to load debugging or performance-measurement libraries into specific sessions without requiring an explicit LOAD command. To that end, it would be typical to set this parameter using the PGOPTIONS environment variable on the client or by using ALTER ROLE SET. However, unless a module is specifically designed to be used in this way by non-superusers, this is usually not the right setting to use. Look at session_preload_libraries instead.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Causes each attempted connection to the server to be logged, as well as successful completion of client authentication. Only superusers can change this parameter at session start, and it cannot be changed at all within a session. The default is off. Note: Some client programs, like psql, attempt to connect twice while determining if a password is required, so duplicate "connection received" messages do not necessarily indicate a problem.
+Causes each attempted connection to the server to be logged, as well as successful completion of client authentication. Only superusers can change this parameter at session start, and it cannot be changed at all within a session. The default is off. Note Some client programs, like psql, attempt to connect twice while determining if a password is required, so duplicate “connection received” messages do not necessarily indicate a problem.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-PostgreSQL supports several methods for logging server messages, including stderr, csvlog and syslog. On Windows, eventlog is also supported. Set this parameter to a list of desired log destinations separated by commas. The default is to log to stderr only. This parameter can only be set in the postgresql.conf file or on the server command line. If csvlog is included in log_destination, log entries are output in "comma separated value" (CSV) format, which is convenient for loading logs into programs. See Section 19.8.4 for details. logging_collector must be enabled to generate CSV-format log output. Note: On most Unix systems, you will need to alter the configuration of your system's syslog daemon in order to make use of the syslog option for log_destination. PostgreSQL can log to syslog facilities LOCAL0 through LOCAL7 (see syslog_facility), but the default syslog configuration on most platforms will discard all such messages. You will need to add something like: local0.* /var/log/postgresql to the syslog daemon's configuration file to make it work. On Windows, when you use the eventlog option for log_destination, you should register an event source and its library with the operating system so that the Windows Event Viewer can display event log messages cleanly. See Section 18.11 for details.
+PostgreSQL supports several methods for logging server messages, including stderr, csvlog and syslog. On Windows, eventlog is also supported. Set this parameter to a list of desired log destinations separated by commas. The default is to log to stderr only. This parameter can only be set in the postgresql.conf file or on the server command line. If csvlog is included in log_destination, log entries are output in “comma separated value” (CSV) format, which is convenient for loading logs into programs. See Section 19.8.4 for details. logging_collector must be enabled to generate CSV-format log output. When either stderr or csvlog are included, the file current_logfiles is created to record the location of the log file(s) currently in use by the logging collector and the associated logging destination. This provides a convenient way to find the logs currently in use by the instance. Here is an example of this file's content: stderr log/postgresql.log csvlog log/postgresql.csv current_logfiles is recreated when a new log file is created as an effect of rotation, and when log_destination is reloaded. It is removed when neither stderr nor csvlog are included in log_destination, and when the logging collector is disabled. Note On most Unix systems, you will need to alter the configuration of your system's syslog daemon in order to make use of the syslog option for log_destination. PostgreSQL can log to syslog facilities LOCAL0 through LOCAL7 (see syslog_facility), but the default syslog configuration on most platforms will discard all such messages. You will need to add something like: local0.* /var/log/postgresql to the syslog daemon's configuration file to make it work. On Windows, when you use the eventlog option for log_destination, you should register an event source and its library with the operating system so that the Windows Event Viewer can display event log messages cleanly. See Section 18.11 for details.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
 context: sighup
-boot_val: pg_log
+boot_val: log
 unit: None
 enumvals: None
 
-When logging_collector is enabled, this parameter determines the directory in which log files will be created. It can be specified as an absolute path, or relative to the cluster data directory. This parameter can only be set in the postgresql.conf file or on the server command line. The default is pg_log.
+When logging_collector is enabled, this parameter determines the directory in which log files will be created. It can be specified as an absolute path, or relative to the cluster data directory. This parameter can only be set in the postgresql.conf file or on the server command line. The default is log.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Causes the duration of every completed statement to be logged. The default is off. Only superusers can change this setting. For clients using extended query protocol, durations of the Parse, Bind, and Execute steps are logged independently. Note: The difference between setting this option and setting log_min_duration_statement to zero is that exceeding log_min_duration_statement forces the text of the query to be logged, but this option doesn't. Thus, if log_duration is on and log_min_duration_statement has a positive value, all durations are logged but the query text is included only for statements exceeding the threshold. This behavior can be useful for gathering statistics in high-load installations.
+Causes the duration of every completed statement to be logged. The default is off. Only superusers can change this setting. For clients using extended query protocol, durations of the Parse, Bind, and Execute steps are logged independently. Note The difference between setting this option and setting log_min_duration_statement to zero is that exceeding log_min_duration_statement forces the text of the query to be logged, but this option doesn't. Thus, if log_duration is on and log_min_duration_statement has a positive value, all durations are logged but the query text is included only for statements exceeding the threshold. This behavior can be useful for gathering statistics in high-load installations.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
 context: sighup
-boot_val: 
+boot_val: %m [%p] 
 unit: None
 enumvals: None
 
-This is a printf-style string that is output at the beginning of each log line. % characters begin "escape sequences" that are replaced with status information as outlined below. Unrecognized escapes are ignored. Other characters are copied straight to the log line. Some escapes are only recognized by session processes, and will be treated as empty by background processes such as the main server process. Status information may be aligned either left or right by specifying a numeric literal after the % and before the option. A negative value will cause the status information to be padded on the right with spaces to give it a minimum width, whereas a positive value will pad on the left. Padding can be useful to aid human readability in log files. This parameter can only be set in the postgresql.conf file or on the server command line. The default is an empty string. Escape Effect Session only %a Application name yes %u User name yes %d Database name yes %r Remote host name or IP address, and remote port yes %h Remote host name or IP address yes %p Process ID no %t Time stamp without milliseconds no %m Time stamp with milliseconds no %n Time stamp with milliseconds (as a Unix epoch) no %i Command tag: type of session's current command yes %e SQLSTATE error code no %c Session ID: see below no %l Number of the log line for each session or process, starting at 1 no %s Process start time stamp no %v Virtual transaction ID (backendID/localXID) no %x Transaction ID (0 if none is assigned) no %q Produces no output, but tells non-session processes to stop at this point in the string; ignored by session processes no %% Literal % no The %c escape prints a quasi-unique session identifier, consisting of two 4-byte hexadecimal numbers (without leading zeros) separated by a dot. The numbers are the process start time and the process ID, so %c can also be used as a space saving way of printing those items. For example, to generate the session identifier from pg_stat_activity, use this query: SELECT to_hex(trunc(EXTRACT(EPOCH FROM backend_start))::integer) || '.' || to_hex(pid) FROM pg_stat_activity; Tip: If you set a nonempty value for log_line_prefix, you should usually make its last character be a space, to provide visual separation from the rest of the log line. A punctuation character can be used too. Tip: Syslog produces its own time stamp and process ID information, so you probably do not want to include those escapes if you are logging to syslog.
+This is a printf-style string that is output at the beginning of each log line. % characters begin “escape sequences” that are replaced with status information as outlined below. Unrecognized escapes are ignored. Other characters are copied straight to the log line. Some escapes are only recognized by session processes, and will be treated as empty by background processes such as the main server process. Status information may be aligned either left or right by specifying a numeric literal after the % and before the option. A negative value will cause the status information to be padded on the right with spaces to give it a minimum width, whereas a positive value will pad on the left. Padding can be useful to aid human readability in log files. This parameter can only be set in the postgresql.conf file or on the server command line. The default is '%m [%p] ' which logs a time stamp and the process ID. Escape Effect Session only %a Application name yes %u User name yes %d Database name yes %r Remote host name or IP address, and remote port yes %h Remote host name or IP address yes %p Process ID no %t Time stamp without milliseconds no %m Time stamp with milliseconds no %n Time stamp with milliseconds (as a Unix epoch) no %i Command tag: type of session's current command yes %e SQLSTATE error code no %c Session ID: see below no %l Number of the log line for each session or process, starting at 1 no %s Process start time stamp no %v Virtual transaction ID (backendID/localXID) no %x Transaction ID (0 if none is assigned) no %q Produces no output, but tells non-session processes to stop at this point in the string; ignored by session processes no %% Literal % no The %c escape prints a quasi-unique session identifier, consisting of two 4-byte hexadecimal numbers (without leading zeros) separated by a dot. The numbers are the process start time and the process ID, so %c can also be used as a space saving way of printing those items. For example, to generate the session identifier from pg_stat_activity, use this query: SELECT to_hex(trunc(EXTRACT(EPOCH FROM backend_start))::integer) || '.' || to_hex(pid) FROM pg_stat_activity; Tip If you set a nonempty value for log_line_prefix, you should usually make its last character be a space, to provide visual separation from the rest of the log line. A punctuation character can be used too. Tip Syslog produces its own time stamp and process ID information, so you probably do not want to include those escapes if you are logging to syslog. Tip The %q escape is useful when including information that is only available in session (backend) context like user or database name. For example: log_line_prefix = '%m [%p] %q%u@%d/%a '

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: ms
 enumvals: None
 
-Causes the duration of each completed statement to be logged if the statement ran for at least the specified number of milliseconds. Setting this to zero prints all statement durations. Minus-one (the default) disables logging statement durations. For example, if you set it to 250ms then all SQL statements that run 250ms or longer will be logged. Enabling this parameter can be helpful in tracking down unoptimized queries in your applications. Only superusers can change this setting. For clients using extended query protocol, durations of the Parse, Bind, and Execute steps are logged independently. Note: When using this option together with log_statement, the text of statements that are logged because of log_statement will not be repeated in the duration log message. If you are not using syslog, it is recommended that you log the PID or session ID using log_line_prefix so that you can link the statement message to the later duration message using the process ID or session ID.
+Causes the duration of each completed statement to be logged if the statement ran for at least the specified number of milliseconds. Setting this to zero prints all statement durations. Minus-one (the default) disables logging statement durations. For example, if you set it to 250ms then all SQL statements that run 250ms or longer will be logged. Enabling this parameter can be helpful in tracking down unoptimized queries in your applications. Only superusers can change this setting. For clients using extended query protocol, durations of the Parse, Bind, and Execute steps are logged independently. Note When using this option together with log_statement, the text of statements that are logged because of log_statement will not be repeated in the duration log message. If you are not using syslog, it is recommended that you log the PID or session ID using log_line_prefix so that you can link the statement message to the later duration message using the process ID or session ID.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Causes each replication command to be logged in the server log. See Section 51.3 for more information about replication command. The default value is off. Only superusers can change this setting.
+Causes each replication command to be logged in the server log. See Section 52.4 for more information about replication command. The default value is off. Only superusers can change this setting.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: ['none', 'ddl', 'mod', 'all']
 
-Controls which SQL statements are logged. Valid values are none (off), ddl, mod, and all (all statements). ddl logs all data definition statements, such as CREATE, ALTER, and DROP statements. mod logs all ddl statements, plus data-modifying statements such as INSERT, UPDATE, DELETE, TRUNCATE, and COPY FROM. PREPARE, EXECUTE, and EXPLAIN ANALYZE statements are also logged if their contained command is of an appropriate type. For clients using extended query protocol, logging occurs when an Execute message is received, and values of the Bind parameters are included (with any embedded single-quote marks doubled). The default is none. Only superusers can change this setting. Note: Statements that contain simple syntax errors are not logged even by the log_statement = all setting, because the log message is emitted only after basic parsing has been done to determine the statement type. In the case of extended query protocol, this setting likewise does not log statements that fail before the Execute phase (i.e., during parse analysis or planning). Set log_min_error_statement to ERROR (or lower) to log such statements.
+Controls which SQL statements are logged. Valid values are none (off), ddl, mod, and all (all statements). ddl logs all data definition statements, such as CREATE, ALTER, and DROP statements. mod logs all ddl statements, plus data-modifying statements such as INSERT, UPDATE, DELETE, TRUNCATE, and COPY FROM. PREPARE, EXECUTE, and EXPLAIN ANALYZE statements are also logged if their contained command is of an appropriate type. For clients using extended query protocol, logging occurs when an Execute message is received, and values of the Bind parameters are included (with any embedded single-quote marks doubled). The default is none. Only superusers can change this setting. Note Statements that contain simple syntax errors are not logged even by the log_statement = all setting, because the log message is emitted only after basic parsing has been done to determine the statement type. In the case of extended query protocol, this setting likewise does not log statements that fail before the Execute phase (i.e., during parse analysis or planning). Set log_min_error_statement to ERROR (or lower) to log such statements. Logged statements might reveal sensitive data and even contain plaintext passwords.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-This parameter enables the logging collector, which is a background process that captures log messages sent to stderr and redirects them into log files. This approach is often more useful than logging to syslog, since some types of messages might not appear in syslog output. (One common example is dynamic-linker failure messages; another is error messages produced by scripts such as archive_command.) This parameter can only be set at server start. Note: It is possible to log to stderr without using the logging collector; the log messages will just go to wherever the server's stderr is directed. However, that method is only suitable for low log volumes, since it provides no convenient way to rotate log files. Also, on some platforms not using the logging collector can result in lost or garbled log output, because multiple processes writing concurrently to the same log file can overwrite each other's output. Note: The logging collector is designed to never lose messages. This means that in case of extremely high load, server processes could be blocked while trying to send additional log messages when the collector has fallen behind. In contrast, syslog prefers to drop messages if it cannot write them, which means it may fail to log some messages in such cases but it will not block the rest of the system.
+This parameter enables the logging collector, which is a background process that captures log messages sent to stderr and redirects them into log files. This approach is often more useful than logging to syslog, since some types of messages might not appear in syslog output. (One common example is dynamic-linker failure messages; another is error messages produced by scripts such as archive_command.) This parameter can only be set at server start. Note It is possible to log to stderr without using the logging collector; the log messages will just go to wherever the server's stderr is directed. However, that method is only suitable for low log volumes, since it provides no convenient way to rotate log files. Also, on some platforms not using the logging collector can result in lost or garbled log output, because multiple processes writing concurrently to the same log file can overwrite each other's output. Note The logging collector is designed to never lose messages. This means that in case of extremely high load, server processes could be blocked while trying to send additional log messages when the collector has fallen behind. In contrast, syslog prefers to drop messages if it cannot write them, which means it may fail to log some messages in such cases but it will not block the rest of the system.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Sets the maximum number of simultaneously open files allowed to each server subprocess. The default is one thousand files. If the kernel is enforcing a safe per-process limit, you don't need to worry about this setting. But on some platforms (notably, most BSD systems), the kernel will allow individual processes to open many more files than the system can actually support if many processes all try to open that many files. If you find yourself seeing "Too many open files" failures, try reducing this setting. This parameter can only be set at server start.
+Sets the maximum number of simultaneously open files allowed to each server subprocess. The default is one thousand files. If the kernel is enforcing a safe per-process limit, you don't need to worry about this setting. But on some platforms (notably, most BSD systems), the kernel will allow individual processes to open many more files than the system can actually support if many processes all try to open that many files. If you find yourself seeing “Too many open files” failures, try reducing this setting. This parameter can only be set at server start.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: integer
+context: postmaster
+boot_val: 4
+unit: None
+enumvals: None
+
+Specifies maximum number of logical replication workers. This includes both apply workers and table synchronization workers. Logical replication workers are taken from the pool defined by max_worker_processes. The default value is 4. This parameter can only be set at server start.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: integer
+context: user
+boot_val: 8
+unit: None
+enumvals: None
+
+Sets the maximum number of workers that the system can support for parallel queries. The default value is 8. When increasing or decreasing this value, consider also adjusting max_parallel_workers_per_gather. Also, note that a setting for this value which is higher than max_worker_processes will have no effect, since parallel workers are taken from the pool of worker processes established by that setting.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: integer
 context: user
-boot_val: 0
+boot_val: 2
 unit: None
 enumvals: None
 
-Sets the maximum number of workers that can be started by a single Gather node. Parallel workers are taken from the pool of processes established by max_worker_processes. Note that the requested number of workers may not actually be available at run time. If this occurs, the plan will run with fewer workers than expected, which may be inefficient. Setting this value to 0, which is the default, disables parallel query execution. Note that parallel queries may consume very substantially more resources than non-parallel queries, because each worker process is a completely separate process which has roughly the same impact on the system as an additional user session. This should be taken into account when choosing a value for this setting, as well as when configuring other settings that control resource utilization, such as work_mem. Resource limits such as work_mem are applied individually to each worker, which means the total utilization may be much higher across all processes than it would normally be for any single process. For example, a parallel query using 4 workers may use up to 5 times as much CPU time, memory, I/O bandwidth, and so forth as a query which uses no workers at all. For more information on parallel query, see Chapter 15.
+Sets the maximum number of workers that can be started by a single Gather or Gather Merge node. Parallel workers are taken from the pool of processes established by max_worker_processes, limited by max_parallel_workers. Note that the requested number of workers may not actually be available at run time. If this occurs, the plan will run with fewer workers than expected, which may be inefficient. The default value is 2. Setting this value to 0 disables parallel query execution. Note that parallel queries may consume very substantially more resources than non-parallel queries, because each worker process is a completely separate process which has roughly the same impact on the system as an additional user session. This should be taken into account when choosing a value for this setting, as well as when configuring other settings that control resource utilization, such as work_mem. Resource limits such as work_mem are applied individually to each worker, which means the total utilization may be much higher across all processes than it would normally be for any single process. For example, a parallel query using 4 workers may use up to 5 times as much CPU time, memory, I/O bandwidth, and so forth as a query which uses no workers at all. For more information on parallel query, see Chapter 15.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: integer
+context: sighup
+boot_val: 2
+unit: None
+enumvals: None
+
+This controls how many rows on a single page can be predicate-locked before the lock is promoted to covering the whole page. The default is 2. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: integer
+context: sighup
+boot_val: -2
+unit: None
+enumvals: None
+
+This controls how many pages or tuples of a single relation can be predicate-locked before the lock is promoted to covering the whole relation. Values greater than or equal to zero mean an absolute limit, while negative values mean max_pred_locks_per_transaction divided by the absolute value of this setting. The default is -2, which keeps the behavior from previous versions of PostgreSQL. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Sets the maximum number of transactions that can be in the "prepared" state simultaneously (see PREPARE TRANSACTION). Setting this parameter to zero (which is the default) disables the prepared-transaction feature. This parameter can only be set at server start. If you are not planning to use prepared transactions, this parameter should be set to zero to prevent accidental creation of prepared transactions. If you are using prepared transactions, you will probably want max_prepared_transactions to be at least as large as max_connections, so that every session can have a prepared transaction pending. When running a standby server, you must set this parameter to the same or higher value than on the master server. Otherwise, queries will not be allowed in the standby server.
+Sets the maximum number of transactions that can be in the “prepared” state simultaneously (see PREPARE TRANSACTION). Setting this parameter to zero (which is the default) disables the prepared-transaction feature. This parameter can only be set at server start. If you are not planning to use prepared transactions, this parameter should be set to zero to prevent accidental creation of prepared transactions. If you are using prepared transactions, you will probably want max_prepared_transactions to be at least as large as max_connections, so that every session can have a prepared transaction pending. When running a standby server, you must set this parameter to the same or higher value than on the master server. Otherwise, queries will not be allowed in the standby server.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: integer
 context: postmaster
-boot_val: 0
+boot_val: 10
 unit: None
 enumvals: None
 
-Specifies the maximum number of replication slots (see Section 26.2.6) that the server can support. The default is zero. This parameter can only be set at server start. wal_level must be set to replica or higher to allow replication slots to be used. Setting it to a lower value than the number of currently existing replication slots will prevent the server from starting.
+Specifies the maximum number of replication slots (see Section 26.2.6) that the server can support. The default is 10. This parameter can only be set at server start. wal_level must be set to replica or higher to allow replication slots to be used. Setting it to a lower value than the number of currently existing replication slots will prevent the server from starting. On the subscriber side, specifies how many replication origins (see Chapter 49) can be tracked simultaneously, effectively limiting how many logical replication subscriptions can be created on the server. Setting it a lower value than the current number of tracked replication origins (reflected in pg_replication_origin_status, not pg_replication_origin) will prevent the server from starting.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: integer
+context: sighup
+boot_val: 2
+unit: None
+enumvals: None
+
+Maximum number of synchronization workers per subscription. This parameter controls the amount of parallelism of the initial data copy during the subscription initialization or when new tables are added. Currently, there can be only one synchronization worker per table. The synchronization workers are taken from the pool defined by max_logical_replication_workers. The default value is 2. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: integer
 context: postmaster
-boot_val: 0
+boot_val: 10
 unit: None
 enumvals: None
 
-Specifies the maximum number of concurrent connections from standby servers or streaming base backup clients (i.e., the maximum number of simultaneously running WAL sender processes). The default is zero, meaning replication is disabled. WAL sender processes count towards the total number of connections, so the parameter cannot be set higher than max_connections. Abrupt streaming client disconnection might cause an orphaned connection slot until a timeout is reached, so this parameter should be set slightly higher than the maximum number of expected clients so disconnected clients can immediately reconnect. This parameter can only be set at server start. wal_level must be set to replica or higher to allow connections from standby servers.
+Specifies the maximum number of concurrent connections from standby servers or streaming base backup clients (i.e., the maximum number of simultaneously running WAL sender processes). The default is 10. The value 0 means replication is disabled. WAL sender processes count towards the total number of connections, so the parameter cannot be set higher than max_connections. Abrupt streaming client disconnection might cause an orphaned connection slot until a timeout is reached, so this parameter should be set slightly higher than the maximum number of expected clients so disconnected clients can immediately reconnect. This parameter can only be set at server start. wal_level must be set to replica or higher to allow connections from standby servers.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: integer
 context: sighup
-boot_val: 64
-unit: 16MB
+boot_val: 1024
+unit: MB
 enumvals: None
 
 Maximum size to let the WAL grow during automatic checkpoints. This is a soft limit; WAL size can exceed max_wal_size under special circumstances, like under heavy load, a failing archive_command, or a high wal_keep_segments setting. The default is 1 GB. Increasing this parameter can increase the amount of time needed for crash recovery. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Sets the maximum number of background processes that the system can support. This parameter can only be set at server start. The default is 8. When running a standby server, you must set this parameter to the same or higher value than on the master server. Otherwise, queries will not be allowed in the standby server.
+Sets the maximum number of background processes that the system can support. This parameter can only be set at server start. The default is 8. When running a standby server, you must set this parameter to the same or higher value than on the master server. Otherwise, queries will not be allowed in the standby server. When changing this value, consider also adjusting max_parallel_workers and max_parallel_workers_per_gather.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: integer
+context: user
+boot_val: 64
+unit: 8kB
+enumvals: None
+
+Sets the minimum amount of index data that must be scanned in order for a parallel scan to be considered. Note that a parallel index scan typically won't touch the entire index; it is the number of pages which the planner believes will actually be touched by the scan which is relevant. The default is 512 kilobytes (512kB).

--- 9.6
+++ 10
@@ -1,7 +0,0 @@
-vartype: integer
-context: user
-boot_val: 1024
-unit: 8kB
-enumvals: None
-
-Sets the minimum size of relations to be considered for parallel scan. The default is 8 megabytes (8MB).

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: integer
+context: user
+boot_val: 1024
+unit: 8kB
+enumvals: None
+
+Sets the minimum amount of table data that must be scanned in order for a parallel scan to be considered. For a parallel sequential scan, the amount of table data scanned is always equal to the size of the table, but when indexes are used the amount of table data scanned will normally be less. The default is 8 megabytes (8MB).

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: integer
 context: sighup
-boot_val: 5
-unit: 16MB
+boot_val: 80
+unit: MB
 enumvals: None
 
 As long as WAL disk usage stays below this setting, old WAL files are always recycled for future use at a checkpoint, rather than removed. This can be used to ensure that enough WAL space is reserved to handle spikes in WAL usage, for example when running large batch jobs. The default is 80 MB. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: min
 enumvals: None
 
-Sets the minimum time that a snapshot can be used without risk of a snapshot too old error occurring when using the snapshot. This parameter can only be set at server start. Beyond the threshold, old data may be vacuumed away. This can help prevent bloat in the face of snapshots which remain in use for a long time. To prevent incorrect results due to cleanup of data which would otherwise be visible to the snapshot, an error is generated when the snapshot is older than this threshold and the snapshot is used to read a page which has been modified since the snapshot was built. A value of -1 disables this feature, and is the default. Useful values for production work probably range from a small number of hours to a few days. The setting will be coerced to a granularity of minutes, and small numbers (such as 0 or 1min) are only allowed because they may sometimes be useful for testing. While a setting as high as 60d is allowed, please note that in many workloads extreme bloat or transaction ID wraparound may occur in much shorter time frames. When this feature is enabled, freed space at the end of a relation cannot be released to the operating system, since that could remove information needed to detect the snapshot too old condition. All space allocated to a relation remains associated with that relation for reuse only within that relation unless explicitly freed (for example, with VACUUM FULL). This setting does not attempt to guarantee that an error will be generated under any particular circumstances. In fact, if the correct results can be generated from (for example) a cursor which has materialized a result set, no error will be generated even if the underlying rows in the referenced table have been vacuumed away. Some tables cannot safely be vacuumed early, and so will not be affected by this setting. Examples include system catalogs and any table which has a hash index. For such tables this setting will neither reduce bloat nor create a possibility of a snapshot too old error on scanning.
+Sets the minimum time that a snapshot can be used without risk of a snapshot too old error occurring when using the snapshot. This parameter can only be set at server start. Beyond the threshold, old data may be vacuumed away. This can help prevent bloat in the face of snapshots which remain in use for a long time. To prevent incorrect results due to cleanup of data which would otherwise be visible to the snapshot, an error is generated when the snapshot is older than this threshold and the snapshot is used to read a page which has been modified since the snapshot was built. A value of -1 disables this feature, and is the default. Useful values for production work probably range from a small number of hours to a few days. The setting will be coerced to a granularity of minutes, and small numbers (such as 0 or 1min) are only allowed because they may sometimes be useful for testing. While a setting as high as 60d is allowed, please note that in many workloads extreme bloat or transaction ID wraparound may occur in much shorter time frames. When this feature is enabled, freed space at the end of a relation cannot be released to the operating system, since that could remove information needed to detect the snapshot too old condition. All space allocated to a relation remains associated with that relation for reuse only within that relation unless explicitly freed (for example, with VACUUM FULL). This setting does not attempt to guarantee that an error will be generated under any particular circumstances. In fact, if the correct results can be generated from (for example) a cursor which has materialized a result set, no error will be generated even if the underlying rows in the referenced table have been vacuumed away. Some tables cannot safely be vacuumed early, and so will not be affected by this setting, such as system catalogs. For such tables this setting will neither reduce bloat nor create a possibility of a snapshot too old error on scanning.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
-vartype: bool
+vartype: enum
 context: user
-boot_val: on
+boot_val: md5
 unit: None
-enumvals: None
+enumvals: ['md5', 'scram-sha-256']
 
-When a password is specified in CREATE USER or ALTER ROLE without writing either ENCRYPTED or UNENCRYPTED, this parameter determines whether the password is to be encrypted. The default is on (encrypt the password).
+When a password is specified in CREATE ROLE or ALTER ROLE, this parameter determines the algorithm to use to encrypt the password. The default value is md5, which stores the password as an MD5 hash (on is also accepted, as alias for md5). Setting this parameter to scram-sha-256 will encrypt the password with SCRAM-SHA-256. Note that older clients might lack support for the SCRAM authentication mechanism, and hence not work with passwords encrypted with SCRAM-SHA-256. See Section 20.3.2 for more details.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Sets the planner's estimate of the cost of a non-sequentially-fetched disk page. The default is 4.0. This value can be overridden for tables and indexes in a particular tablespace by setting the tablespace parameter of the same name (see ALTER TABLESPACE). Reducing this value relative to seq_page_cost will cause the system to prefer index scans; raising it will make index scans look relatively more expensive. You can raise or lower both values together to change the importance of disk I/O costs relative to CPU costs, which are described by the following parameters. Random access to mechanical disk storage is normally much more expensive than four times sequential access. However, a lower default is used (4.0) because the majority of random accesses to disk, such as indexed reads, are assumed to be in cache. The default value can be thought of as modeling random access as 40 times slower than sequential, while expecting 90% of random reads to be cached. If you believe a 90% cache rate is an incorrect assumption for your workload, you can increase random_page_cost to better reflect the true cost of random storage reads. Correspondingly, if your data is likely to be completely in cache, such as when the database is smaller than the total server memory, decreasing random_page_cost can be appropriate. Storage that has a low random read cost relative to sequential, e.g., solid-state drives, might also be better modeled with a lower value for random_page_cost, e.g., 1.1. Tip: Although the system will let you set random_page_cost to less than seq_page_cost, it is not physically sensible to do so. However, setting them equal makes sense if the database is entirely cached in RAM, since in that case there is no penalty for touching pages out of sequence. Also, in a heavily-cached database you should lower both values relative to the CPU parameters, since the cost of fetching a page already in RAM is much smaller than it would normally be.
+Sets the planner's estimate of the cost of a non-sequentially-fetched disk page. The default is 4.0. This value can be overridden for tables and indexes in a particular tablespace by setting the tablespace parameter of the same name (see ALTER TABLESPACE). Reducing this value relative to seq_page_cost will cause the system to prefer index scans; raising it will make index scans look relatively more expensive. You can raise or lower both values together to change the importance of disk I/O costs relative to CPU costs, which are described by the following parameters. Random access to mechanical disk storage is normally much more expensive than four times sequential access. However, a lower default is used (4.0) because the majority of random accesses to disk, such as indexed reads, are assumed to be in cache. The default value can be thought of as modeling random access as 40 times slower than sequential, while expecting 90% of random reads to be cached. If you believe a 90% cache rate is an incorrect assumption for your workload, you can increase random_page_cost to better reflect the true cost of random storage reads. Correspondingly, if your data is likely to be completely in cache, such as when the database is smaller than the total server memory, decreasing random_page_cost can be appropriate. Storage that has a low random read cost relative to sequential, e.g., solid-state drives, might also be better modeled with a lower value for random_page_cost, e.g., 1.1. Tip Although the system will let you set random_page_cost to less than seq_page_cost, it is not physically sensible to do so. However, setting them equal makes sense if the database is entirely cached in RAM, since in that case there is no penalty for touching pages out of sequence. Also, in a heavily-cached database you should lower both values relative to the CPU parameters, since the cost of fetching a page already in RAM is much smaller than it would normally be.

--- 9.6
+++ 10
@@ -1,6 +1,6 @@
 vartype: string
 context: internal
-boot_val: 9.6.24
+boot_val: 10.23 (Debian 10.23-1.pgdg110+1)
 unit: None
 enumvals: None
 

--- 9.6
+++ 10
@@ -1,6 +1,6 @@
 vartype: integer
 context: internal
-boot_val: 90624
+boot_val: 100023
 unit: None
 enumvals: None
 

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-This variable specifies one or more shared libraries that are to be preloaded at connection start. Only superusers can change this setting. The parameter value only takes effect at the start of the connection. Subsequent changes have no effect. If a specified library is not found, the connection attempt will fail. The intent of this feature is to allow debugging or performance-measurement libraries to be loaded into specific sessions without an explicit LOAD command being given. For example, auto_explain could be enabled for all sessions under a given user name by setting this parameter with ALTER ROLE SET. Also, this parameter can be changed without restarting the server (but changes only take effect when a new session is started), so it is easier to add new modules this way, even if they should apply to all sessions. Unlike shared_preload_libraries, there is no large performance advantage to loading a library at session start rather than when it is first used. There is some advantage, however, when connection pooling is used.
+This variable specifies one or more shared libraries that are to be preloaded at connection start. It contains a comma-separated list of library names, where each name is interpreted as for the LOAD command. Whitespace between entries is ignored; surround a library name with double quotes if you need to include whitespace or commas in the name. The parameter value only takes effect at the start of the connection. Subsequent changes have no effect. If a specified library is not found, the connection attempt will fail. Only superusers can change this setting. The intent of this feature is to allow debugging or performance-measurement libraries to be loaded into specific sessions without an explicit LOAD command being given. For example, auto_explain could be enabled for all sessions under a given user name by setting this parameter with ALTER ROLE SET. Also, this parameter can be changed without restarting the server (but changes only take effect when a new session is started), so it is easier to add new modules this way, even if they should apply to all sessions. Unlike shared_preload_libraries, there is no large performance advantage to loading a library at session start rather than when it is first used. There is some advantage, however, when connection pooling is used.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: 8kB
 enumvals: None
 
-Sets the amount of memory the database server uses for shared memory buffers. The default is typically 128 megabytes (128MB), but might be less if your kernel settings will not support it (as determined during initdb). This setting must be at least 128 kilobytes. (Non-default values of BLCKSZ change the minimum.) However, settings significantly higher than the minimum are usually needed for good performance. This parameter can only be set at server start. If you have a dedicated database server with 1GB or more of RAM, a reasonable starting value for shared_buffers is 25% of the memory in your system. There are some workloads where even large settings for shared_buffers are effective, but because PostgreSQL also relies on the operating system cache, it is unlikely that an allocation of more than 40% of RAM to shared_buffers will work better than a smaller amount. Larger settings for shared_buffers usually require a corresponding increase in max_wal_size, in order to spread out the process of writing large quantities of new or changed data over a longer period of time. On systems with less than 1GB of RAM, a smaller percentage of RAM is appropriate, so as to leave adequate space for the operating system. Also, on Windows, large values for shared_buffers aren't as effective. You may find better results keeping the setting relatively low and using the operating system cache more instead. The useful range for shared_buffers on Windows systems is generally from 64MB to 512MB.
+Sets the amount of memory the database server uses for shared memory buffers. The default is typically 128 megabytes (128MB), but might be less if your kernel settings will not support it (as determined during initdb). This setting must be at least 128 kilobytes. (Non-default values of BLCKSZ change the minimum.) However, settings significantly higher than the minimum are usually needed for good performance. This parameter can only be set at server start. If you have a dedicated database server with 1GB or more of RAM, a reasonable starting value for shared_buffers is 25% of the memory in your system. There are some workloads where even larger settings for shared_buffers are effective, but because PostgreSQL also relies on the operating system cache, it is unlikely that an allocation of more than 40% of RAM to shared_buffers will work better than a smaller amount. Larger settings for shared_buffers usually require a corresponding increase in max_wal_size, in order to spread out the process of writing large quantities of new or changed data over a longer period of time. On systems with less than 1GB of RAM, a smaller percentage of RAM is appropriate, so as to leave adequate space for the operating system.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-This variable specifies one or more shared libraries to be preloaded at server start. This parameter can only be set at server start. If a specified library is not found, the server will fail to start. Some libraries need to perform certain operations that can only take place at postmaster start, such as allocating shared memory, reserving light-weight locks, or starting background workers. Those libraries must be loaded at server start through this parameter. See the documentation of each library for details. Other libraries can also be preloaded. By preloading a shared library, the library startup time is avoided when the library is first used. However, the time to start each new server process might increase slightly, even if that process never uses the library. So this parameter is recommended only for libraries that will be used in most sessions. Also, changing this parameter requires a server restart, so this is not the right setting to use for short-term debugging tasks, say. Use session_preload_libraries for that instead. Note: On Windows hosts, preloading a library at server start will not reduce the time required to start each new server process; each server process will re-load all preload libraries. However, shared_preload_libraries is still useful on Windows hosts for libraries that need to perform operations at postmaster start time.
+This variable specifies one or more shared libraries to be preloaded at server start. It contains a comma-separated list of library names, where each name is interpreted as for the LOAD command. Whitespace between entries is ignored; surround a library name with double quotes if you need to include whitespace or commas in the name. This parameter can only be set at server start. If a specified library is not found, the server will fail to start. Some libraries need to perform certain operations that can only take place at postmaster start, such as allocating shared memory, reserving light-weight locks, or starting background workers. Those libraries must be loaded at server start through this parameter. See the documentation of each library for details. Other libraries can also be preloaded. By preloading a shared library, the library startup time is avoided when the library is first used. However, the time to start each new server process might increase slightly, even if that process never uses the library. So this parameter is recommended only for libraries that will be used in most sessions. Also, changing this parameter requires a server restart, so this is not the right setting to use for short-term debugging tasks, say. Use session_preload_libraries for that instead. Note On Windows hosts, preloading a library at server start will not reduce the time required to start each new server process; each server process will re-load all preload libraries. However, shared_preload_libraries is still useful on Windows hosts for libraries that need to perform operations at postmaster start time.

--- 9.6
+++ 10
@@ -1,7 +0,0 @@
-vartype: bool
-context: user
-boot_val: on
-unit: None
-enumvals: None
-
-This setting controls whether undecorated table references are considered to include inheritance child tables. The default is on, which means child tables are included (thus, a * suffix is assumed by default). If turned off, child tables are not included (thus, an ONLY prefix is assumed). The SQL standard requires child tables to be included, so the off setting is not spec-compliant, but it is provided for compatibility with PostgreSQL releases prior to 7.1. See Section 5.9 for more information. Turning sql_inheritance off is deprecated, because that behavior has been found to be error-prone as well as contrary to SQL standard. Discussions of inheritance behavior elsewhere in this manual generally assume that it is on.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: bool
-context: postmaster
+context: sighup
 boot_val: off
 unit: None
 enumvals: None
 
-Enables SSL connections. Please read Section 18.9 before using this. The default is off. This parameter can only be set at server start. SSL communication is only possible with TCP/IP connections.
+Enables SSL connections. Please read Section 18.9 before using this. This parameter can only be set in the postgresql.conf file or on the server command line. The default is off.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
-context: postmaster
+context: sighup
 boot_val: 
 unit: None
 enumvals: None
 
-Specifies the name of the file containing the SSL server certificate authority (CA). The default is empty, meaning no CA file is loaded, and client certificate verification is not performed. (In previous releases of PostgreSQL, the name of this file was hard-coded as root.crt.) Relative paths are relative to the data directory. This parameter can only be set at server start.
+Specifies the name of the file containing the SSL server certificate authority (CA). Relative paths are relative to the data directory. This parameter can only be set in the postgresql.conf file or on the server command line. The default is empty, meaning no CA file is loaded, and client certificate verification is not performed. In previous releases of PostgreSQL, the name of this file was hard-coded as root.crt.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
-context: postmaster
+context: sighup
 boot_val: server.crt
 unit: None
 enumvals: None
 
-Specifies the name of the file containing the SSL server certificate. The default is server.crt. Relative paths are relative to the data directory. This parameter can only be set at server start.
+Specifies the name of the file containing the SSL server certificate. Relative paths are relative to the data directory. This parameter can only be set in the postgresql.conf file or on the server command line. The default is server.crt.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
-context: postmaster
+context: sighup
 boot_val: HIGH:MEDIUM:+3DES:!aNULL
 unit: None
 enumvals: None
 
-Specifies a list of SSL cipher suites that are allowed to be used by SSL connections. See the ciphers manual page in the OpenSSL package for the syntax of this setting and a list of supported values. Only connections using TLS version 1.2 and lower are affected. There is currently no setting that controls the cipher choices used by TLS version 1.3 connections. The default value is HIGH:MEDIUM:+3DES:!aNULL. It is usually reasonable, unless you have specific security requirements. This parameter can only be set at server start. Explanation of the default value: HIGH Cipher suites that use ciphers from HIGH group (e.g., AES, Camellia, 3DES) MEDIUM Cipher suites that use ciphers from MEDIUM group (e.g., RC4, SEED) +3DES The OpenSSL default order for HIGH is problematic because it orders 3DES higher than AES128. This is wrong because 3DES offers less security than AES128, and it is also much slower. +3DES reorders it after all other HIGH and MEDIUM ciphers. !aNULL Disables anonymous cipher suites that do no authentication. Such cipher suites are vulnerable to man-in-the-middle attacks and therefore should not be used. Available cipher suite details will vary across OpenSSL versions. Use the command openssl ciphers -v 'HIGH:MEDIUM:+3DES:!aNULL' to see actual details for the currently installed OpenSSL version. Note that this list is filtered at run time based on the server key type.
+Specifies a list of SSL cipher suites that are allowed to be used by SSL connections. See the ciphers manual page in the OpenSSL package for the syntax of this setting and a list of supported values. Only connections using TLS version 1.2 and lower are affected. There is currently no setting that controls the cipher choices used by TLS version 1.3 connections. The default value is HIGH:MEDIUM:+3DES:!aNULL. The default is usually a reasonable choice unless you have specific security requirements. This parameter can only be set in the postgresql.conf file or on the server command line. Explanation of the default value: HIGH Cipher suites that use ciphers from HIGH group (e.g., AES, Camellia, 3DES) MEDIUM Cipher suites that use ciphers from MEDIUM group (e.g., RC4, SEED) +3DES The OpenSSL default order for HIGH is problematic because it orders 3DES higher than AES128. This is wrong because 3DES offers less security than AES128, and it is also much slower. +3DES reorders it after all other HIGH and MEDIUM ciphers. !aNULL Disables anonymous cipher suites that do no authentication. Such cipher suites are vulnerable to man-in-the-middle attacks and therefore should not be used. Available cipher suite details will vary across OpenSSL versions. Use the command openssl ciphers -v 'HIGH:MEDIUM:+3DES:!aNULL' to see actual details for the currently installed OpenSSL version. Note that this list is filtered at run time based on the server key type.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
-context: postmaster
+context: sighup
 boot_val: 
 unit: None
 enumvals: None
 
-Specifies the name of the file containing the SSL server certificate revocation list (CRL). The default is empty, meaning no CRL file is loaded. (In previous releases of PostgreSQL, the name of this file was hard-coded as root.crl.) Relative paths are relative to the data directory. This parameter can only be set at server start.
+Specifies the name of the file containing the SSL client certificate revocation list (CRL). Relative paths are relative to the data directory. This parameter can only be set in the postgresql.conf file or on the server command line. The default is empty, meaning no CRL file is loaded. In previous releases of PostgreSQL, the name of this file was hard-coded as root.crl.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: string
+context: sighup
+boot_val: 
+unit: None
+enumvals: None
+
+Specifies the name of the file containing Diffie-Hellman parameters used for so-called ephemeral DH family of SSL ciphers. The default is empty, in which case compiled-in default DH parameters used. Using custom DH parameters reduces the exposure if an attacker manages to crack the well-known compiled-in DH parameters. You can create your own DH parameters file with the command openssl dhparam -out dhparams.pem 2048. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
-context: postmaster
+context: sighup
 boot_val: prime256v1
 unit: None
 enumvals: None
 
-Specifies the name of the curve to use in ECDH key exchange. It needs to be supported by all clients that connect. It does not need to be same curve as used by server's Elliptic Curve key. The default is prime256v1. This parameter can only be set at server start. OpenSSL names for most common curves: prime256v1 (NIST P-256), secp384r1 (NIST P-384), secp521r1 (NIST P-521). The full list of available curves can be shown with the command openssl ecparam -list_curves. Not all of them are usable in TLS though.
+Specifies the name of the curve to use in ECDH key exchange. It needs to be supported by all clients that connect. It does not need to be the same curve used by the server's Elliptic Curve key. This parameter can only be set in the postgresql.conf file or on the server command line. The default is prime256v1. OpenSSL names for the most common curves are: prime256v1 (NIST P-256), secp384r1 (NIST P-384), secp521r1 (NIST P-521). The full list of available curves can be shown with the command openssl ecparam -list_curves. Not all of them are usable in TLS though.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: string
-context: postmaster
+context: sighup
 boot_val: server.key
 unit: None
 enumvals: None
 
-Specifies the name of the file containing the SSL server private key. The default is server.key. Relative paths are relative to the data directory. This parameter can only be set at server start.
+Specifies the name of the file containing the SSL server private key. Relative paths are relative to the data directory. This parameter can only be set in the postgresql.conf file or on the server command line. The default is server.key.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: bool
-context: postmaster
+context: sighup
 boot_val: on
 unit: None
 enumvals: None
 
-Specifies whether to use the server's SSL cipher preferences, rather than the client's. The default is true. This parameter can only be set at server start. Older PostgreSQL versions do not have this setting and always use the client's preferences. This setting is mainly for backward compatibility with those versions. Using the server's preferences is usually better because it is more likely that the server is appropriately configured.
+Specifies whether to use the server's SSL cipher preferences, rather than the client's. This parameter can only be set in the postgresql.conf file or on the server command line. The default is true. Older PostgreSQL versions do not have this setting and always use the client's preferences. This setting is mainly for backward compatibility with those versions. Using the server's preferences is usually better because it is more likely that the server is appropriately configured.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Determines the number of connection "slots" that are reserved for connections by PostgreSQL superusers. At most max_connections connections can ever be active simultaneously. Whenever the number of active concurrent connections is at least max_connections minus superuser_reserved_connections, new connections will be accepted only for superusers, and no new replication connections will be accepted. The default value is three connections. The value must be less than the value of max_connections. This parameter can only be set at server start.
+Determines the number of connection “slots” that are reserved for connections by PostgreSQL superusers. At most max_connections connections can ever be active simultaneously. Whenever the number of active concurrent connections is at least max_connections minus superuser_reserved_connections, new connections will be accepted only for superusers, and no new replication connections will be accepted. The default value is three connections. The value must be less than the value of max_connections. This parameter can only be set at server start.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-This allows sequential scans of large tables to synchronize with each other, so that concurrent scans read the same block at about the same time and hence share the I/O workload. When this is enabled, a scan might start in the middle of the table and then "wrap around" the end to cover all rows, so as to synchronize with the activity of scans already in progress. This can result in unpredictable changes in the row ordering returned by queries that have no ORDER BY clause. Setting this parameter to off ensures the pre-8.3 behavior in which a sequential scan always starts from the beginning of the table. The default is on.
+This allows sequential scans of large tables to synchronize with each other, so that concurrent scans read the same block at about the same time and hence share the I/O workload. When this is enabled, a scan might start in the middle of the table and then “wrap around” the end to cover all rows, so as to synchronize with the activity of scans already in progress. This can result in unpredictable changes in the row ordering returned by queries that have no ORDER BY clause. Setting this parameter to off ensures the pre-8.3 behavior in which a sequential scan always starts from the beginning of the table. The default is on.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: ['local', 'remote_write', 'remote_apply', 'on', 'off']
 
-Specifies how much WAL processing must complete before the database server returns a "success" indication to the client. Valid values are remote_apply, on (the default), remote_write, local, and off. If synchronous_standby_names is empty, the only meaningful settings are on and off; remote_apply, remote_write and local all provide the same local synchronization level as on. The local behavior of all non-off modes is to wait for local flush of WAL to disk. In off mode, there is no waiting, so there can be a delay between when success is reported to the client and when the transaction is later guaranteed to be safe against a server crash. (The maximum delay is three times wal_writer_delay.) Unlike fsync, setting this parameter to off does not create any risk of database inconsistency: an operating system or database crash might result in some recent allegedly-committed transactions being lost, but the database state will be just the same as if those transactions had been aborted cleanly. So, turning synchronous_commit off can be a useful alternative when performance is more important than exact certainty about the durability of a transaction. For more discussion see Section 30.3. If synchronous_standby_names is non-empty, synchronous_commit also controls whether transaction commits will wait for their WAL records to be processed on the standby server(s). When set to remote_apply, commits will wait until replies from the current synchronous standby(s) indicate they have received the commit record of the transaction and applied it, so that it has become visible to queries on the standby(s), and also written to durable storage on the standbys. This will cause much larger commit delays than previous settings since it waits for WAL replay. When set to on, commits wait until replies from the current synchronous standby(s) indicate they have received the commit record of the transaction and flushed it to durable storage. This ensures the transaction will not be lost unless both the primary and all synchronous standbys suffer corruption of their database storage. When set to remote_write, commits will wait until replies from the current synchronous standby(s) indicate they have received the commit record of the transaction and written it to their file systems. This setting ensures data preservation if a standby instance of PostgreSQL crashes, but not if the standby suffers an operating-system-level crash because the data has not necessarily reached durable storage on the standby. The setting local causes commits to wait for local flush to disk, but not for replication. This is usually not desirable when synchronous replication is in use, but is provided for completeness. This parameter can be changed at any time; the behavior for any one transaction is determined by the setting in effect when it commits. It is therefore possible, and useful, to have some transactions commit synchronously and others asynchronously. For example, to make a single multistatement transaction commit asynchronously when the default is the opposite, issue SET LOCAL synchronous_commit TO OFF within the transaction. Table 19-1 summarizes the capabilities of the synchronous_commit settings. Table 19-1. synchronous_commit Modes synchronous_commit setting local durable commit standby durable commit after PG crash standby durable commit after OS crash standby query consistency remote_apply • • • • on • • • remote_write • • local • off
+Specifies how much WAL processing must complete before the database server returns a “success” indication to the client. Valid values are remote_apply, on (the default), remote_write, local, and off. If synchronous_standby_names is empty, the only meaningful settings are on and off; remote_apply, remote_write and local all provide the same local synchronization level as on. The local behavior of all non-off modes is to wait for local flush of WAL to disk. In off mode, there is no waiting, so there can be a delay between when success is reported to the client and when the transaction is later guaranteed to be safe against a server crash. (The maximum delay is three times wal_writer_delay.) Unlike fsync, setting this parameter to off does not create any risk of database inconsistency: an operating system or database crash might result in some recent allegedly-committed transactions being lost, but the database state will be just the same as if those transactions had been aborted cleanly. So, turning synchronous_commit off can be a useful alternative when performance is more important than exact certainty about the durability of a transaction. For more discussion see Section 30.3. If synchronous_standby_names is non-empty, synchronous_commit also controls whether transaction commits will wait for their WAL records to be processed on the standby server(s). When set to remote_apply, commits will wait until replies from the current synchronous standby(s) indicate they have received the commit record of the transaction and applied it, so that it has become visible to queries on the standby(s), and also written to durable storage on the standbys. This will cause much larger commit delays than previous settings since it waits for WAL replay. When set to on, commits wait until replies from the current synchronous standby(s) indicate they have received the commit record of the transaction and flushed it to durable storage. This ensures the transaction will not be lost unless both the primary and all synchronous standbys suffer corruption of their database storage. When set to remote_write, commits will wait until replies from the current synchronous standby(s) indicate they have received the commit record of the transaction and written it to their file systems. This setting ensures data preservation if a standby instance of PostgreSQL crashes, but not if the standby suffers an operating-system-level crash because the data has not necessarily reached durable storage on the standby. The setting local causes commits to wait for local flush to disk, but not for replication. This is usually not desirable when synchronous replication is in use, but is provided for completeness. This parameter can be changed at any time; the behavior for any one transaction is determined by the setting in effect when it commits. It is therefore possible, and useful, to have some transactions commit synchronously and others asynchronously. For example, to make a single multistatement transaction commit asynchronously when the default is the opposite, issue SET LOCAL synchronous_commit TO OFF within the transaction. Table 19.1 summarizes the capabilities of the synchronous_commit settings. Table 19.1. synchronous_commit Modes synchronous_commit setting local durable commit standby durable commit after PG crash standby durable commit after OS crash standby query consistency remote_apply • • • • on • • • remote_write • • local • off

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Specifies a list of standby servers that can support synchronous replication, as described in Section 26.2.8. There will be one or more active synchronous standbys; transactions waiting for commit will be allowed to proceed after these standby servers confirm receipt of their data. The synchronous standbys will be those whose names appear earlier in this list, and that are both currently connected and streaming data in real-time (as shown by a state of streaming in the pg_stat_replication view). Other standby servers appearing later in this list represent potential synchronous standbys. If any of the current synchronous standbys disconnects for whatever reason, it will be replaced immediately with the next-highest-priority standby. Specifying more than one standby name can allow very high availability. This parameter specifies a list of standby servers using either of the following syntaxes: num_sync ( standby_name [, ...] ) standby_name [, ...] where num_sync is the number of synchronous standbys that transactions need to wait for replies from, and standby_name is the name of a standby server. For example, a setting of 3 (s1, s2, s3, s4) makes transaction commits wait until their WAL records are received by three higher-priority standbys chosen from standby servers s1, s2, s3 and s4. The second syntax was used before PostgreSQL version 9.6 and is still supported. It's the same as the first syntax with num_sync equal to 1. For example, 1 (s1, s2) and s1, s2 have the same meaning: either s1 or s2 is chosen as a synchronous standby. The name of a standby server for this purpose is the application_name setting of the standby, as set in the primary_conninfo of the standby's WAL receiver. There is no mechanism to enforce uniqueness. In case of duplicates one of the matching standbys will be considered as higher priority, though exactly which one is indeterminate. The special entry * matches any application_name, including the default application name of walreceiver. Note: Each standby_name should have the form of a valid SQL identifier, unless it is *. You can use double-quoting if necessary. But note that standby_names are compared to standby application names case-insensitively, whether double-quoted or not. If no synchronous standby names are specified here, then synchronous replication is not enabled and transaction commits will not wait for replication. This is the default configuration. Even when synchronous replication is enabled, individual transactions can be configured not to wait for replication by setting the synchronous_commit parameter to local or off. This parameter can only be set in the postgresql.conf file or on the server command line.
+Specifies a list of standby servers that can support synchronous replication, as described in Section 26.2.8. There will be one or more active synchronous standbys; transactions waiting for commit will be allowed to proceed after these standby servers confirm receipt of their data. The synchronous standbys will be those whose names appear in this list, and that are both currently connected and streaming data in real-time (as shown by a state of streaming in the pg_stat_replication view). Specifying more than one synchronous standby can allow for very high availability and protection against data loss. The name of a standby server for this purpose is the application_name setting of the standby, as set in the standby's connection information. In case of a physical replication standby, this should be set in the primary_conninfo setting in recovery.conf; the default is walreceiver. For logical replication, this can be set in the connection information of the subscription, and it defaults to the subscription name. For other replication stream consumers, consult their documentation. This parameter specifies a list of standby servers using either of the following syntaxes: [FIRST] num_sync ( standby_name [, ...] ) ANY num_sync ( standby_name [, ...] ) standby_name [, ...] where num_sync is the number of synchronous standbys that transactions need to wait for replies from, and standby_name is the name of a standby server. FIRST and ANY specify the method to choose synchronous standbys from the listed servers. The keyword FIRST, coupled with num_sync, specifies a priority-based synchronous replication and makes transaction commits wait until their WAL records are replicated to num_sync synchronous standbys chosen based on their priorities. For example, a setting of FIRST 3 (s1, s2, s3, s4) will cause each commit to wait for replies from three higher-priority standbys chosen from standby servers s1, s2, s3 and s4. The standbys whose names appear earlier in the list are given higher priority and will be considered as synchronous. Other standby servers appearing later in this list represent potential synchronous standbys. If any of the current synchronous standbys disconnects for whatever reason, it will be replaced immediately with the next-highest-priority standby. The keyword FIRST is optional. The keyword ANY, coupled with num_sync, specifies a quorum-based synchronous replication and makes transaction commits wait until their WAL records are replicated to at least num_sync listed standbys. For example, a setting of ANY 3 (s1, s2, s3, s4) will cause each commit to proceed as soon as at least any three standbys of s1, s2, s3 and s4 reply. FIRST and ANY are case-insensitive. If these keywords are used as the name of a standby server, its standby_name must be double-quoted. The third syntax was used before PostgreSQL version 9.6 and is still supported. It's the same as the first syntax with FIRST and num_sync equal to 1. For example, FIRST 1 (s1, s2) and s1, s2 have the same meaning: either s1 or s2 is chosen as a synchronous standby. The special entry * matches any standby name. There is no mechanism to enforce uniqueness of standby names. In case of duplicates one of the matching standbys will be considered as higher priority, though exactly which one is indeterminate. Note Each standby_name should have the form of a valid SQL identifier, unless it is *. You can use double-quoting if necessary. But note that standby_names are compared to standby application names case-insensitively, whether double-quoted or not. If no synchronous standby names are specified here, then synchronous replication is not enabled and transaction commits will not wait for replication. This is the default configuration. Even when synchronous replication is enabled, individual transactions can be configured not to wait for replication by setting the synchronous_commit parameter to local or off. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: ['local0', 'local1', 'local2', 'local3', 'local4', 'local5', 'local6', 'local7']
 
-When logging to syslog is enabled, this parameter determines the syslog "facility" to be used. You can choose from LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7; the default is LOCAL0. See also the documentation of your system's syslog daemon. This parameter can only be set in the postgresql.conf file or on the server command line.
+When logging to syslog is enabled, this parameter determines the syslog “facility” to be used. You can choose from LOCAL0, LOCAL1, LOCAL2, LOCAL3, LOCAL4, LOCAL5, LOCAL6, LOCAL7; the default is LOCAL0. See also the documentation of your system's syslog daemon. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-When logging to syslog and this is on (the default), then each message will be prefixed by an increasing sequence number (such as [2]). This circumvents the "--- last message repeated N times ---" suppression that many syslog implementations perform by default. In more modern syslog implementations, repeated message suppression can be configured (for example, $RepeatedMsgReduction in rsyslog), so this might not be necessary. Also, you could turn this off if you actually want to suppress repeated messages. This parameter can only be set in the postgresql.conf file or on the server command line.
+When logging to syslog and this is on (the default), then each message will be prefixed by an increasing sequence number (such as [2]). This circumvents the “--- last message repeated N times ---” suppression that many syslog implementations perform by default. In more modern syslog implementations, repeated message suppression can be configured (for example, $RepeatedMsgReduction in rsyslog), so this might not be necessary. Also, you could turn this off if you actually want to suppress repeated messages. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Specifies the number of TCP keepalives that can be lost before the server's connection to the client is considered dead. A value of 0 uses the system default. This parameter is supported only on systems that support TCP_KEEPCNT or an equivalent socket option; on other systems, it must be zero. In sessions connected via a Unix-domain socket, this parameter is ignored and always reads as zero. Note: This parameter is not supported on Windows, and must be zero.
+Specifies the number of TCP keepalives that can be lost before the server's connection to the client is considered dead. A value of 0 uses the system default. This parameter is supported only on systems that support TCP_KEEPCNT or an equivalent socket option; on other systems, it must be zero. In sessions connected via a Unix-domain socket, this parameter is ignored and always reads as zero. Note This parameter is not supported on Windows, and must be zero.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: s
 enumvals: None
 
-Specifies the number of seconds of inactivity after which TCP should send a keepalive message to the client. A value of 0 uses the system default. This parameter is supported only on systems that support TCP_KEEPIDLE or an equivalent socket option, and on Windows; on other systems, it must be zero. In sessions connected via a Unix-domain socket, this parameter is ignored and always reads as zero. Note: On Windows, a value of 0 will set this parameter to 2 hours, since Windows does not provide a way to read the system default value.
+Specifies the number of seconds of inactivity after which TCP should send a keepalive message to the client. A value of 0 uses the system default. This parameter is supported only on systems that support TCP_KEEPIDLE or an equivalent socket option, and on Windows; on other systems, it must be zero. In sessions connected via a Unix-domain socket, this parameter is ignored and always reads as zero. Note On Windows, a value of 0 will set this parameter to 2 hours, since Windows does not provide a way to read the system default value.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: s
 enumvals: None
 
-Specifies the number of seconds after which a TCP keepalive message that is not acknowledged by the client should be retransmitted. A value of 0 uses the system default. This parameter is supported only on systems that support TCP_KEEPINTVL or an equivalent socket option, and on Windows; on other systems, it must be zero. In sessions connected via a Unix-domain socket, this parameter is ignored and always reads as zero. Note: On Windows, a value of 0 will set this parameter to 1 second, since Windows does not provide a way to read the system default value.
+Specifies the number of seconds after which a TCP keepalive message that is not acknowledged by the client should be retransmitted. A value of 0 uses the system default. This parameter is supported only on systems that support TCP_KEEPINTVL or an equivalent socket option, and on Windows; on other systems, it must be zero. In sessions connected via a Unix-domain socket, this parameter is ignored and always reads as zero. Note On Windows, a value of 0 will set this parameter to 1 second, since Windows does not provide a way to read the system default value.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Enables the collection of information on the currently executing command of each session, along with the time when that command began execution. This parameter is on by default. Note that even when enabled, this information is not visible to all users, only to superusers and the user owning the session being reported on, so it should not represent a security risk. Only superusers can change this setting.
+Enables the collection of information on the currently executing command of each session, along with the time when that command began execution. This parameter is on by default. Note that even when enabled, this information is not visible to all users, only to superusers, roles with privileges of the pg_read_all_stats role and the user owning the sessions being reported on (including sessions belonging to a role they have the privileges of), so it should not represent a security risk. Only superusers can change this setting.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: ['none', 'pl', 'all']
 
-Enables tracking of function call counts and time used. Specify pl to track only procedural-language functions, all to also track SQL and C language functions. The default is none, which disables function statistics tracking. Only superusers can change this setting. Note: SQL-language functions that are simple enough to be "inlined" into the calling query will not be tracked, regardless of this setting.
+Enables tracking of function call counts and time used. Specify pl to track only procedural-language functions, all to also track SQL and C language functions. The default is none, which disables function statistics tracking. Only superusers can change this setting. Note SQL-language functions that are simple enough to be “inlined” into the calling query will not be tracked, regardless of this setting.

--- 9.6
+++ 10
@@ -0,0 +1,7 @@
+vartype: string
+context: superuser
+boot_val: 
+unit: None
+enumvals: None
+
+This parameter is intended to be used to check for bugs in the WAL redo routines. When enabled, full-page images of any buffers modified in conjunction with the WAL record are added to the record. If the record is subsequently replayed, the system will first apply each record and then test whether the buffers modified by the record match the stored images. In certain cases (such as hint bits), minor variations are acceptable, and will be ignored. Any unexpected differences will result in a fatal error, terminating recovery. The default value of this setting is the empty string, which disables the feature. It can be set to all to check all records, or to a comma-separated list of resource managers to check only records originating from those resource managers. Currently, the supported resource managers are heap, heap2, btree, hash, gin, gist, sequence, spgist, brin, and generic. Only superusers can change this setting.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: None
 enumvals: None
 
-Specifies the minimum number of past log file segments kept in the pg_xlog directory, in case a standby server needs to fetch them for streaming replication. Each segment is normally 16 megabytes. If a standby server connected to the sending server falls behind by more than wal_keep_segments segments, the sending server might remove a WAL segment still needed by the standby, in which case the replication connection will be terminated. Downstream connections will also eventually fail as a result. (However, the standby server can recover by fetching the segment from archive, if WAL archiving is in use.) This sets only the minimum number of segments retained in pg_xlog; the system might need to retain more segments for WAL archival or to recover from a checkpoint. If wal_keep_segments is zero (the default), the system doesn't keep any extra segments for standby purposes, so the number of old WAL segments available to standby servers is a function of the location of the previous checkpoint and status of WAL archiving. This parameter can only be set in the postgresql.conf file or on the server command line.
+Specifies the minimum number of past log file segments kept in the pg_wal directory, in case a standby server needs to fetch them for streaming replication. Each segment is normally 16 megabytes. If a standby server connected to the sending server falls behind by more than wal_keep_segments segments, the sending server might remove a WAL segment still needed by the standby, in which case the replication connection will be terminated. Downstream connections will also eventually fail as a result. (However, the standby server can recover by fetching the segment from archive, if WAL archiving is in use.) This sets only the minimum number of segments retained in pg_wal; the system might need to retain more segments for WAL archival or to recover from a checkpoint. If wal_keep_segments is zero (the default), the system doesn't keep any extra segments for standby purposes, so the number of old WAL segments available to standby servers is a function of the location of the previous checkpoint and status of WAL archiving. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 9.6
+++ 10
@@ -1,7 +1,7 @@
 vartype: enum
 context: postmaster
-boot_val: minimal
+boot_val: replica
 unit: None
 enumvals: ['minimal', 'replica', 'logical']
 
-wal_level determines how much information is written to the WAL. The default value is minimal, which writes only the information needed to recover from a crash or immediate shutdown. replica adds logging required for WAL archiving as well as information required to run read-only queries on a standby server. Finally, logical adds information necessary to support logical decoding. Each level includes the information logged at all lower levels. This parameter can only be set at server start. In minimal level, WAL-logging of some bulk operations can be safely skipped, which can make those operations much faster (see Section 14.4.7). Operations in which this optimization can be applied include: CREATE TABLE AS CREATE INDEX CLUSTER COPY into tables that were created or truncated in the same transaction But minimal WAL does not contain enough information to reconstruct the data from a base backup and the WAL logs, so replica or higher must be used to enable WAL archiving (archive_mode) and streaming replication. In logical level, the same information is logged as with replica, plus information needed to allow extracting logical change sets from the WAL. Using a level of logical will increase the WAL volume, particularly if many tables are configured for REPLICA IDENTITY FULL and many UPDATE and DELETE statements are executed. In releases prior to 9.6, this parameter also allowed the values archive and hot_standby. These are still accepted but mapped to replica.
+wal_level determines how much information is written to the WAL. The default value is replica, which writes enough data to support WAL archiving and replication, including running read-only queries on a standby server. minimal removes all logging except the information required to recover from a crash or immediate shutdown. Finally, logical adds information necessary to support logical decoding. Each level includes the information logged at all lower levels. This parameter can only be set at server start. In minimal level, WAL-logging of some bulk operations can be safely skipped, which can make those operations much faster (see Section 14.4.7). Operations in which this optimization can be applied include: CREATE TABLE AS CREATE INDEX CLUSTER COPY into tables that were created or truncated in the same transaction But minimal WAL does not contain enough information to reconstruct the data from a base backup and the WAL logs, so replica or higher must be used to enable WAL archiving (archive_mode) and streaming replication. In logical level, the same information is logged as with replica, plus information needed to allow extracting logical change sets from the WAL. Using a level of logical will increase the WAL volume, particularly if many tables are configured for REPLICA IDENTITY FULL and many UPDATE and DELETE statements are executed. In releases prior to 9.6, this parameter also allowed the values archive and hot_standby. These are still accepted but mapped to replica.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: s
 enumvals: None
 
-Specifies the minimum frequency for the WAL receiver process on the standby to send information about replication progress to the primary or upstream standby, where it can be seen using the pg_stat_replication view. The standby will report the last transaction log position it has written, the last position it has flushed to disk, and the last position it has applied. This parameter's value is the maximum interval, in seconds, between reports. Updates are sent each time the write or flush positions change, or at least as often as specified by this parameter. Thus, the apply position may lag slightly behind the true position. Setting this parameter to zero disables status updates completely. This parameter can only be set in the postgresql.conf file or on the server command line. The default value is 10 seconds.
+Specifies the minimum frequency for the WAL receiver process on the standby to send information about replication progress to the primary or upstream standby, where it can be seen using the pg_stat_replication view. The standby will report the last write-ahead log location it has written, the last position it has flushed to disk, and the last position it has applied. This parameter's value is the maximum interval, in seconds, between reports. Updates are sent each time the write or flush positions change, or at least as often as specified by this parameter. Thus, the apply position may lag slightly behind the true position. Setting this parameter to zero disables status updates completely. This parameter can only be set in the postgresql.conf file or on the server command line. The default value is 10 seconds.

--- 9.6
+++ 10
@@ -4,4 +4,4 @@
 unit: ms
 enumvals: None
 
-Specify how long the standby server should wait when WAL data is not available from any sources (streaming replication, local pg_xlog or WAL archive) before retrying to retrieve WAL data. This parameter can only be set in the postgresql.conf file or on the server command line. The default value is 5 seconds. Units are milliseconds if not specified. This parameter is useful in configurations where a node in recovery needs to control the amount of time to wait for new WAL data to be available. For example, in archive recovery, it is possible to make the recovery more responsive in the detection of a new WAL log file by reducing the value of this parameter. On a system with low WAL activity, increasing it reduces the amount of requests necessary to access WAL archives, something useful for example in cloud environments where the amount of times an infrastructure is accessed is taken into account.
+Specify how long the standby server should wait when WAL data is not available from any sources (streaming replication, local pg_wal or WAL archive) before retrying to retrieve WAL data. This parameter can only be set in the postgresql.conf file or on the server command line. The default value is 5 seconds. Units are milliseconds if not specified. This parameter is useful in configurations where a node in recovery needs to control the amount of time to wait for new WAL data to be available. For example, in archive recovery, it is possible to make the recovery more responsive in the detection of a new WAL log file by reducing the value of this parameter. On a system with low WAL activity, increasing it reduces the amount of requests necessary to access WAL archives, something useful for example in cloud environments where the amount of times an infrastructure is accessed is taken into account.