What changed?

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the display format for date and time values, as well as the rules for interpreting ambiguous date input values. For historical reasons, this variable contains two independent components: the output format specification (ISO, Postgres, SQL, or German) and the input/output specification for year/month/day ordering (DMY, MDY, or YMD). These can be set separately or together. The keywords Euro and European are synonyms for DMY; the keywords US, NonEuro, and NonEuropean are synonyms for MDY. See Section 8.5 for more information. The default is ISO, MDY.
+Sets the display format for date and time values, as well as the rules for interpreting ambiguous date input values. For historical reasons, this variable contains two independent components: the output format specification (ISO, Postgres, SQL, or German) and the input/output specification for year/month/day ordering (DMY, MDY, or YMD). These can be set separately or together. The keywords Euro and European are synonyms for DMY; the keywords US, NonEuro, and NonEuropean are synonyms for MDY. See Section 8.5 for more information. The built-in default is ISO, MDY, but initdb will initialize the configuration file with a setting that corresponds to the behavior of the chosen lc_time locale.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Allows modification of the structure of system tables. This is used by initdb. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-The shell command to execute to archive a completed segment of the WAL file series. If this is an empty string (the default), WAL archiving is disabled. Any %p in the string is replaced by the path name of the file to archive, and any %f is replaced by the file name only. (The path name is relative to the working directory of the server, i.e., the cluster's data directory.) Use %% to embed an actual % character in the command. For more information see Section 23.3.1. This option can only be set at server start or in the postgresql.conf file. It is important for the command to return a zero exit status if and only if it succeeds. Examples: archive_command = 'cp "%p" /mnt/server/archivedir/"%f"' archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Windows
+The shell command to execute to archive a completed segment of the WAL file series. If this is an empty string (the default), WAL archiving is disabled. Any %p in the string is replaced by the path name of the file to archive, and any %f is replaced by the file name only. (The path name is relative to the working directory of the server, i.e., the cluster's data directory.) Use %% to embed an actual % character in the command. For more information see Section 23.3.1. This parameter can only be set in the postgresql.conf file or on the server command line. It is important for the command to return a zero exit status if and only if it succeeds. Examples: archive_command = 'cp "%p" /mnt/server/archivedir/"%f"' archive_command = 'copy "%p" /mnt/server/archivedir/"%f"' # Windows

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+The archive_command is only invoked on 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 put a limit on 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. 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. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+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 backwards 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.

--- 8.1
+++ 8.2
@@ -1,3 +0,0 @@
-
-
-If set to on, ACST, CST, EST, and SAT are interpreted as Australian time zones rather than as North/South American time zones and Saturday. The default is off.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Maximum time to complete client authentication, in seconds. If a would-be client has not completed the authentication protocol in this much time, the server breaks the connection. This prevents hung clients from occupying a connection indefinitely. This option can be set at server start or in the postgresql.conf file. The default is 60.
+Maximum time to complete client authentication, in seconds. If a would-be client has not completed the authentication protocol in this much time, the server breaks the connection. This prevents hung clients from occupying a connection indefinitely. The default is one minute (1m). This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Controls whether the server should start the autovacuum subprocess. This is off by default. stats_start_collector and stats_row_level must also be on for this to start. This option can be set at server start or in the postgresql.conf file.
+Controls whether the server should run the autovacuum daemon. This is off by default. stats_start_collector and stats_row_level must also be turned on for autovacuum to work. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies a fraction of the table size to add to autovacuum_analyze_threshold when deciding whether to trigger an ANALYZE. The default is 0.2. This option can be set at server start or in the postgresql.conf file. This setting can be overridden for individual tables by entries in pg_autovacuum.
+Specifies a fraction of the table size to add to autovacuum_analyze_threshold when deciding whether to trigger an ANALYZE. The default is 0.1 (10% of table size). This parameter can only be set in the postgresql.conf file or on the server command line. This setting can be overridden for individual tables by entries in pg_autovacuum.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the minimum number of inserted, updated or deleted tuples needed to trigger an ANALYZE in any one table. The default is 500. This option can be set at server start or in the postgresql.conf file. This setting can be overridden for individual tables by entries in pg_autovacuum.
+Specifies the minimum number of inserted, updated or deleted tuples needed to trigger an ANALYZE in any one table. The default is 250 tuples. This parameter can only be set in the postgresql.conf file or on the server command line. This setting can be overridden for individual tables by entries in pg_autovacuum.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+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. The default is 200 million transactions. This parameter can only be set at server start, but the setting can be reduced for individual tables by entries in pg_autovacuum. For more information see Section 22.1.3.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the delay between activity rounds for the autovacuum subprocess. In each round the subprocess examines one database and issues VACUUM and ANALYZE commands as needed for tables in that database. The delay is measured in seconds, and the default is 60. This option can be set at server start or in the postgresql.conf file.
+Specifies the delay between activity rounds for the autovacuum daemon. In each round the daemon examines one database and issues VACUUM and ANALYZE commands as needed for tables in that database. The delay is measured in seconds, and the default is one minute (1m). This parameter can only be set in the postgresql.conf file or on the server command line. Note that even when this parameter is disabled, the system will periodically launch autovacuum processes in order to prevent transaction ID wraparound. See Section 22.1.3 for more information.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the cost delay value that will be used in automatic VACUUM operations. If -1 is specified (which is the default), the regular vacuum_cost_delay value will be used. This setting can be overridden for individual tables by entries in pg_autovacuum.
+Specifies the cost delay value that will be used in automatic VACUUM operations. If -1 is specified (which is the default), the regular vacuum_cost_delay value will be used. This parameter can only be set in the postgresql.conf file or on the server command line. This setting can be overridden for individual tables by entries in pg_autovacuum.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the cost limit value that will be used in automatic VACUUM operations. If -1 is specified (which is the default), the regular vacuum_cost_limit value will be used. This setting can be overridden for individual tables by entries in pg_autovacuum.
+Specifies the cost limit value that will be used in automatic VACUUM operations. If -1 is specified (which is the default), the regular vacuum_cost_limit value will be used. This parameter can only be set in the postgresql.conf file or on the server command line. This setting can be overridden for individual tables by entries in pg_autovacuum.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies a fraction of the table size to add to autovacuum_vacuum_threshold when deciding whether to trigger a VACUUM. The default is 0.4. This option can be set at server start or in the postgresql.conf file. This setting can be overridden for individual tables by entries in pg_autovacuum.
+Specifies a fraction of the table size to add to autovacuum_vacuum_threshold when deciding whether to trigger a VACUUM. The default is 0.2 (20% of table size). This parameter can only be set in the postgresql.conf file or on the server command line. This setting can be overridden for individual tables by entries in pg_autovacuum.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the minimum number of updated or deleted tuples needed to trigger a VACUUM in any one table. The default is 1000. This option can be set at server start or in the postgresql.conf file. This setting can be overridden for individual tables by entries in pg_autovacuum.
+Specifies the minimum number of updated or deleted tuples needed to trigger a VACUUM in any one table. The default is 500 tuples. This parameter can only be set in the postgresql.conf file or on the server command line. This setting can be overridden for individual tables by entries in pg_autovacuum.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This controls whether a quote mark can be represented by \' in a string literal. The preferred, SQL-standard way to represent a quote mark is by doubling it ('') but PostgreSQL has historically also accepted \'. However, use of \' creates security risks because in some client character set encodings, there are multibyte characters in which the last byte is numerically equivalent to ASCII \. If client-side code does escaping incorrectly then a SQL-injection attack is possible. This risk can be prevented by making the server reject queries in which a quote mark appears to be escaped by a backslash. The allowed values of backslash_quote are on (allow \' always), off (reject always), and safe_encoding (allow only if client encoding does not allow ASCII \ within a multibyte character). safe_encoding is the default setting.
+This controls whether a quote mark can be represented by \' in a string literal. The preferred, SQL-standard way to represent a quote mark is by doubling it ('') but PostgreSQL has historically also accepted \'. However, use of \' creates security risks because in some client character set encodings, there are multibyte characters in which the last byte is numerically equivalent to ASCII \. If client-side code does escaping incorrectly then a SQL-injection attack is possible. This risk can be prevented by making the server reject queries in which a quote mark appears to be escaped by a backslash. The allowed values of backslash_quote are on (allow \' always), off (reject always), and safe_encoding (allow only if client encoding does not allow ASCII \ within a multibyte character). safe_encoding is the default setting. Note that in a standard-conforming string literal, \ just means \ anyway. This parameter affects the handling of non-standard-conforming literals, including escape string syntax (E'...').

--- 8.1
+++ 8.2
@@ -1 +1 @@
-In each round, no more than this many buffers will be written as a result of the scan of the entire buffer pool. (If this limit is reached, the scan stops, and resumes at the next buffer during the next round.) The default value is 5. This option can be set at server start or in the postgresql.conf file.
+In each round, no more than this many buffers will be written as a result of the scan of the entire buffer pool. (If this limit is reached, the scan stops, and resumes at the next buffer during the next round.) The default value is five buffers. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-To reduce the amount of work that will be needed at checkpoint time, the background writer also does a circular scan through the entire buffer pool, writing buffers that are found to be dirty. In each round, it examines up to bgwriter_all_percent of the buffers for this purpose. The default value is 0.333 (this is a percentage of the total number of shared buffers). With the default bgwriter_delay setting, this will allow the entire shared buffer pool to be scanned about once per minute. This option can be set at server start or in the postgresql.conf file.
+To reduce the amount of work that will be needed at checkpoint time, the background writer also does a circular scan through the entire buffer pool, writing buffers that are found to be dirty. In each round, it examines up to bgwriter_all_percent of the buffers for this purpose. The default value is 0.333 (0.333% of the total number of shared buffers). With the default bgwriter_delay setting, this will allow the entire shared buffer pool to be scanned about once per minute. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the delay between activity rounds for the background writer. In each round the writer issues writes for some number of dirty buffers (controllable by the following parameters). It then sleeps for bgwriter_delay milliseconds, and repeats. The default value is 200. Note that on many systems, the effective resolution of sleep delays is 10 milliseconds; setting bgwriter_delay to a value that is not a multiple of 10 may have the same results as setting it to the next higher multiple of 10. This option can be set at server start or in the postgresql.conf file.
+Specifies the delay between activity rounds for the background writer. In each round the writer issues writes for some number of dirty buffers (controllable by the following parameters). It then sleeps for bgwriter_delay milliseconds, and repeats. The default value is 200 milliseconds (200ms). Note that on many systems, the effective resolution of sleep delays is 10 milliseconds; setting bgwriter_delay to a value that is not a multiple of 10 may have the same results as setting it to the next higher multiple of 10. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-In each round, no more than this many buffers will be written as a result of scanning soon-to-be-recycled buffers. The default value is 5. This option can be set at server start or in the postgresql.conf file.
+In each round, no more than this many buffers will be written as a result of scanning soon-to-be-recycled buffers. The default value is five buffers. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-To reduce the probability that server processes will need to issue their own writes, the background writer tries to write buffers that are likely to be recycled soon. In each round, it examines up to bgwriter_lru_percent of the buffers that are nearest to being recycled, and writes any that are dirty. The default value is 1.0 (this is a percentage of the total number of shared buffers). This option can be set at server start or in the postgresql.conf file.
+To reduce the probability that server processes will need to issue their own writes, the background writer tries to write buffers that are likely to be recycled soon. In each round, it examines up to bgwriter_lru_percent of the buffers that are nearest to being recycled, and writes any that are dirty. The default value is 1.0 (1% of the total number of shared buffers). This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the Bonjour broadcast name. By default, the computer name is used, specified as an empty string ''. This option is ignored if the server was not compiled with Bonjour support. This option can only be set at server start.
+Specifies the Bonjour broadcast name. The computer name is used if this parameter is set to the empty string '' (which is the default). This parameter is ignored if the server was not compiled with Bonjour support. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Maximum distance between automatic WAL checkpoints, in log file segments (each segment is normally 16 megabytes). The default is three. This option can only be set at server start or in the postgresql.conf file.
+Maximum distance between automatic WAL checkpoints, in log file segments (each segment is normally 16 megabytes). The default is three segments. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Maximum time between automatic WAL checkpoints, in seconds. The default is 300 seconds. This option can only be set at server start or in the postgresql.conf file.
+Maximum time between automatic WAL checkpoints, in seconds. The default is five minutes (5min). This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Write a message to the server log if checkpoints caused by the filling of checkpoint segment files happen closer together than this many seconds (which suggests that checkpoint_segments ought to be raised). The default is 30 seconds. Zero disables the warning.
+Write a message to the server log if checkpoints caused by the filling of checkpoint segment files happen closer together than this many seconds (which suggests that checkpoint_segments ought to be raised). The default is 30 seconds (30s). Zero disables the warning. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Minimum number of concurrent open transactions to require before performing the commit_delay delay. A larger value makes it more probable that at least one other transaction will become ready to commit during the delay interval. The default is five.
+Minimum number of concurrent open transactions to require before performing the commit_delay delay. A larger value makes it more probable that at least one other transaction will become ready to commit during the delay interval. The default is five transactions.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the main server configuration file (customarily called postgresql.conf). This option can only be set on the postmaster command line.
+Specifies the main server configuration file (customarily called postgresql.conf). This parameter can only be set on the postgres command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Enables or disables the query planner's use of table constraints to optimize queries. The default is off. When this parameter is on, the planner compares query conditions with table CHECK constraints, and omits scanning tables for which the conditions contradict the constraints. (Presently this is done only for child tables of inheritance scans.) For example: CREATE TABLE parent(key integer, ...); CREATE TABLE child1000(check (key between 1000 and 1999)) INHERITS(parent); CREATE TABLE child2000(check (key between 2000 and 2999)) INHERITS(parent); ... SELECT * FROM parent WHERE key = 2400; With constraint exclusion enabled, this SELECT will not scan child1000 at all. This can improve performance when inheritance is used to build partitioned tables. Currently, constraint_exclusion is disabled by default because it risks incorrect results if query plans are cached — if a table constraint is changed or dropped, the previously generated plan might now be wrong, and there is no built-in mechanism to force re-planning. (This deficiency will probably be addressed in a future PostgreSQL release.) Another reason for keeping it off is that the constraint checks are relatively expensive, and in many circumstances will yield no savings. It is recommended to turn this on only if you are actually using partitioned tables designed to take advantage of the feature. Refer to Section 5.9 for more information on using constraint exclusion and partitioning.
+Enables or disables the query planner's use of table constraints to optimize queries. The default is off. When this parameter is on, the planner compares query conditions with table CHECK constraints, and omits scanning tables for which the conditions contradict the constraints. For example: CREATE TABLE parent(key integer, ...); CREATE TABLE child1000(check (key between 1000 and 1999)) INHERITS(parent); CREATE TABLE child2000(check (key between 2000 and 2999)) INHERITS(parent); ... SELECT * FROM parent WHERE key = 2400; With constraint exclusion enabled, this SELECT will not scan child1000 at all. This can improve performance when inheritance is used to build partitioned tables. Currently, constraint_exclusion is disabled by default because it risks incorrect results if query plans are cached — if a table constraint is changed or dropped, the previously generated plan might now be wrong, and there is no built-in mechanism to force re-planning. (This deficiency will probably be addressed in a future PostgreSQL release.) Another reason for keeping it off is that the constraint checks are relatively expensive, and in many circumstances will yield no savings. It is recommended to turn this on only if you are actually using partitioned tables designed to take advantage of the feature. Refer to Section 5.9 for more information on using constraint exclusion and partitioning.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the planner's estimate of the cost of processing each index row during an index scan. This is measured as a fraction of the cost of a sequential page fetch. The default is 0.001.
+Sets the planner's estimate of the cost of processing each index entry during an index scan. The default is 0.005.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the planner's estimate of the cost of processing each operator in a WHERE clause. This is measured as a fraction of the cost of a sequential page fetch. The default is 0.0025.
+Sets the planner's estimate of the cost of processing each operator or function executed during a query. The default is 0.0025.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the planner's estimate of the cost of processing each row during a query. This is measured as a fraction of the cost of a sequential page fetch. The default is 0.01.
+Sets the planner's estimate of the cost of processing each row during a query. The default is 0.01.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This variable specifies one or several class names to be used for custom variables, in the form of a comma-separated list. A custom variable is a variable not normally known to PostgreSQL proper but used by some add-on module. Such variables must have names consisting of a class name, a dot, and a variable name. custom_variable_classes specifies all the class names in use in a particular installation. This option can be set at server start or in the postgresql.conf configuration file.
+This variable specifies one or several class names to be used for custom variables, in the form of a comma-separated list. A custom variable is a variable not normally known to PostgreSQL proper but used by some add-on module. Such variables must have names consisting of a class name, a dot, and a variable name. custom_variable_classes specifies all the class names in use in a particular installation. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the directory to use for data storage. This option can only be set at server start.
+Specifies the directory to use for data storage. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This enables per-database user names. It is off by default. 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 option enabled, you can still create ordinary global users. Simply append @ when specifying the user name in the client. The @ will be stripped off before the user name is looked up by the server. 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. The @ will be stripped off before the user name is looked up by the server. Note: This feature is intended as a temporary measure until a complete solution is found. At that time, this option will be removed.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This is the amount of time, in milliseconds, to wait on a lock before checking to see if there is a deadlock condition. The check for deadlock is relatively slow, so the server doesn't run it every time it waits for a lock. We (optimistically?) assume that deadlocks are not common in production applications and just wait on the lock for a while before starting the check for a deadlock. Increasing this value reduces the amount of time wasted in needless deadlock checks, but slows down reporting of real deadlock errors. The default is 1000 (i.e., one second), which is probably about the smallest value you would want in practice. On a heavily loaded server you might want to raise it. Ideally the setting should exceed your typical transaction time, so as to improve the odds that a lock will be released before the waiter decides to check for deadlock.
+This is the amount of time, in milliseconds, to wait on a lock before checking to see if there is a deadlock condition. The check for deadlock is relatively slow, so the server doesn't run it every time it waits for a lock. We (optimistically?) assume that deadlocks are not common in production applications and just wait on the lock for a while before starting the check for a deadlock. Increasing this value reduces the amount of time wasted in needless deadlock checks, but slows down reporting of real deadlock errors. The default is one second (1s), which is probably about the smallest value you would want in practice. On a heavily loaded server you might want to raise it. Ideally the setting should exceed your typical transaction time, so as to improve the odds that a lock will be released before the waiter decides to check for deadlock.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Turns on various assertion checks. This is a debugging aid. If you are experiencing strange problems or crashes you might want to turn this on, as it might expose programming mistakes. To use this option, the macro USE_ASSERT_CHECKING must be defined when PostgreSQL is built (accomplished by the configure option --enable-cassert). Note that debug_assertions defaults to on if PostgreSQL has been built with assertions enabled.
+Turns on various assertion checks. This is a debugging aid. If you are experiencing strange problems or crashes you might want to turn this on, as it might expose programming mistakes. To use this parameter, the macro USE_ASSERT_CHECKING must be defined when PostgreSQL is built (accomplished by the configure option --enable-cassert). Note that debug_assertions defaults to on if PostgreSQL has been built with assertions enabled.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-These options enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These options are off by default.
+These parameters enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These parameters are off by default.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-These options enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These options are off by default.
+These parameters enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These parameters are off by default.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-These options enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These options are off by default.
+These parameters enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These parameters are off by default.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-These options enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These options are off by default.
+These parameters enable various debugging output to be emitted. For each executed query, they print the resulting parse tree, the query rewriter output, or the execution plan. debug_pretty_print indents these displays to produce a more readable but much longer output format. client_min_messages or log_min_messages must be DEBUG1 or lower to actually send this output to the client or the server log, respectively. These parameters are off by default.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This controls whether CREATE TABLE and CREATE TABLE AS include an OID column in newly-created tables, if neither WITH OIDS nor WITHOUT OIDS is specified. It also determines whether OIDs will be included in tables created by SELECT INTO. In PostgreSQL 8.1 default_with_oids is disabled by default; in prior versions of PostgreSQL, it was on by default. The use of OIDs in user tables is considered deprecated, so most installations should leave this variable disabled. Applications that require OIDs for a particular table should specify WITH OIDS when creating the table. This variable can be enabled for compatibility with old applications that do not follow this behavior.
+This controls whether CREATE TABLE and CREATE TABLE AS include an OID column in newly-created tables, if neither WITH OIDS nor WITHOUT OIDS is specified. It also determines whether OIDs will be included in tables created by SELECT INTO. In PostgreSQL 8.1 default_with_oids is off by default; in prior versions of PostgreSQL, it was on by default. The use of OIDs in user tables is considered deprecated, so most installations should leave this variable disabled. Applications that require OIDs for a particular table should specify WITH OIDS when creating the table. This variable can be enabled for compatibility with old applications that do not follow this behavior.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the planner's assumption about the effective size of the disk cache that is available to a single index scan. This is factored into estimates of the cost of using an index; a higher value makes it more likely index scans will be used, a lower value makes it more likely sequential scans will be used. When setting this parameter you should consider both PostgreSQL's shared buffers and the portion of the kernel's disk cache that will be used for PostgreSQL data files. Also, take into account the expected number of concurrent queries using different indexes, since they will have to share the available space. This parameter has no effect on the size of shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The value is measured in disk pages, which are normally 8192 bytes each. The default is 1000.
+Sets the planner's assumption about the effective size of the disk cache that is available to a single query. This is factored into estimates of the cost of using an index; a higher value makes it more likely index scans will be used, a lower value makes it more likely sequential scans will be used. When setting this parameter you should consider both PostgreSQL's shared buffers and the portion of the kernel's disk cache that will be used for PostgreSQL data files. Also, take into account the expected number of concurrent queries on different tables, since they will have to share the available space. This parameter has no effect on the size of shared memory allocated by PostgreSQL, nor does it reserve kernel disk cache; it is used only for estimation purposes. The default is 128 megabytes (128MB).

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When on, a warning is issued if a backslash (\) appears in an ordinary string literal ('...' syntax). The default is off. Escape string syntax (E'...') should be used for escapes, because in future versions of PostgreSQL ordinary strings will have the standard-conforming behavior of treating backslashes literally.
+When on, a warning is issued if a backslash (\) appears in an ordinary string literal ('...' syntax) and standard_conforming_strings is off. The default is on. Applications that wish to use backslash as escape should be modified to use escape string syntax (E'...'), because the default behavior of ordinary strings will change in a future release for SQL compatibility. This variable can be enabled to help detect applications that will break.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the name of an additional process-id (PID) file that the postmaster should create for use by server administration programs. This option can only be set at server start.
+Specifies the name of an additional process-id (PID) file that the server should create for use by server administration programs. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-The planner will merge sub-queries into upper queries if the resulting FROM list would have no more than this many items. Smaller values reduce planning time but may yield inferior query plans. The default is 8. It is usually wise to keep this less than geqo_threshold.
+The planner will merge sub-queries into upper queries if the resulting FROM list would have no more than this many items. Smaller values reduce planning time but may yield inferior query plans. The default is eight. It is usually wise to keep this less than geqo_threshold. For more information see Section 13.3.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-If this option is on, the PostgreSQL server will try to make sure that updates are physically written to disk, by issuing fsync() system calls or various equivalent methods (see wal_sync_method). This ensures that the database cluster can recover to a consistent state after an operating system or hardware crash. However, using fsync results in a performance penalty: when a transaction is committed, PostgreSQL must wait for the operating system to flush the write-ahead log to disk. When fsync is disabled, the operating system is allowed to do its best in buffering, ordering, and delaying writes. This can result in significantly improved performance. However, if the system crashes, the results of the last few committed transactions may be lost in part or whole. In the worst case, unrecoverable data corruption may occur. (Crashes of the database software itself are not a risk factor here. Only an operating-system-level crash creates a risk of corruption.) Due to the risks involved, there is no universally correct setting for fsync. Some administrators always disable fsync, while others only turn it off during initial bulk data loads, where there is a clear restart point if something goes wrong. Others always leave fsync enabled. The default is to enable fsync, for maximum reliability. If you trust your operating system, your hardware, and your utility company (or your battery backup), you can consider disabling fsync. This option can be set at server start or in the postgresql.conf file. If you turn this option off, also consider turning off full_page_writes.
+If this parameter is on, the PostgreSQL server will try to make sure that updates are physically written to disk, by issuing fsync() system calls or various equivalent methods (see wal_sync_method). This ensures that the database cluster can recover to a consistent state after an operating system or hardware crash. However, using fsync results in a performance penalty: when a transaction is committed, PostgreSQL must wait for the operating system to flush the write-ahead log to disk. When fsync is disabled, the operating system is allowed to do its best in buffering, ordering, and delaying writes. This can result in significantly improved performance. However, if the system crashes, the results of the last few committed transactions may be lost in part or whole. In the worst case, unrecoverable data corruption may occur. (Crashes of the database software itself are not a risk factor here. Only an operating-system-level crash creates a risk of corruption.) Due to the risks involved, there is no universally correct setting for fsync. Some administrators always disable fsync, while others only turn it off during initial bulk data loads, where there is a clear restart point if something goes wrong. Others always leave fsync enabled. The default is to enable fsync, for maximum reliability. If you trust your operating system, your hardware, and your utility company (or your battery backup), you can consider disabling fsync. This parameter can only be set in the postgresql.conf file or on the server command line. If you turn this parameter off, also consider turning off full_page_writes.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When this option is on, the PostgreSQL server writes the entire content of each disk page to WAL during the first modification of that page after a checkpoint. This parameter is currently ignored (treated as always on) because turning it off can cause failure to recover from crashes even when no hardware or OS-level error occurred. This will be fixed in some future release, or else the parameter will be removed entirely.
+When this parameter is on, the PostgreSQL server writes the entire content of each disk page to WAL during the first modification of that page after a checkpoint. This is needed because a page write that is in process during an operating system crash might be only partially completed, leading to an on-disk page that contains a mix of old and new data. The row-level change data normally stored in WAL will not be enough to completely restore such a page during post-crash recovery. Storing the full page image guarantees that the page can be correctly restored, but at a price in increasing the amount of data that must be written to WAL. (Because WAL replay always starts from a checkpoint, it is sufficient to do this during the first change of each page after a checkpoint. Therefore, one way to reduce the cost of full-page writes is to increase the checkpoint interval parameters.) Turning this parameter off speeds normal operation, but might lead to a corrupt database after an operating system crash or power failure. The risks are similar to turning off fsync, though smaller. It may be safe to turn off this parameter if you have hardware (such as a battery-backed disk controller) or file-system software that reduces the risk of partial page writes to an acceptably low level (e.g., ReiserFS 4). Turning off this parameter does not affect use of WAL archiving for point-in-time recovery (PITR) (see Section 23.3). This parameter can only be set in the postgresql.conf file or on the server command line. The default is on.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Controls the trade off between planning time and query plan efficiency in GEQO. This variable must be an integer in the range from 1 to 10. The default value is 5. Larger values increase the time spent doing query planning, but also increase the likelihood that an efficient query plan will be chosen. geqo_effort doesn't actually do anything directly; it is only used to compute the default values for the other variables that influence GEQO behavior (described below). If you prefer, you can set the other parameters by hand instead.
+Controls the trade off between planning time and query plan efficiency in GEQO. This variable must be an integer in the range from 1 to 10. The default value is five. Larger values increase the time spent doing query planning, but also increase the likelihood that an efficient query plan will be chosen. geqo_effort doesn't actually do anything directly; it is only used to compute the default values for the other variables that influence GEQO behavior (described below). If you prefer, you can set the other parameters by hand instead.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Use genetic query optimization to plan queries with at least this many FROM items involved. (Note that an outer JOIN construct counts as only one FROM item.) The default is 12. For simpler queries it is usually best to use the deterministic, exhaustive planner, but for queries with many tables the deterministic planner takes too long.
+Use genetic query optimization to plan queries with at least this many FROM items involved. (Note that a FULL OUTER JOIN construct counts as only one FROM item.) The default is 12. For simpler queries it is usually best to use the deterministic, exhaustive planner, but for queries with many tables the deterministic planner takes too long.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Soft upper limit of the size of the set returned by GIN index. For more information see Section 51.4.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the configuration file for host-based authentication (customarily called pg_hba.conf). This option can only be set at server start.
+Specifies the configuration file for host-based authentication (customarily called pg_hba.conf). This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the configuration file for ident authentication (customarily called pg_ident.conf). This option can only be set at server start.
+Specifies the configuration file for ident authentication (customarily called pg_ident.conf). This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Ignore system indexes when reading system tables (but still update the indexes when modifying the tables). This is useful when recovering from damaged system indexes. This parameter cannot be changed after session start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-The planner will rewrite explicit inner JOIN constructs into lists of FROM items whenever a list of no more than this many items in total would result. Prior to PostgreSQL 7.4, joins specified via the JOIN construct would never be reordered by the query planner. The query planner has subsequently been improved so that inner joins written in this form can be reordered; this configuration parameter controls the extent to which this reordering is performed. Note: At present, the order of outer joins specified via the JOIN construct is never adjusted by the query planner; therefore, join_collapse_limit has no effect on this behavior. The planner may be improved to reorder some classes of outer joins in a future release of PostgreSQL. By default, this variable is set the same as from_collapse_limit, which is appropriate for most uses. Setting it to 1 prevents any reordering of inner JOINs. Thus, the explicit join order specified in the query will be the actual order in which the relations are joined. The query planner does not always choose the optimal join order; advanced users may elect to temporarily set this variable to 1, and then specify the join order they desire explicitly. Another consequence of setting this variable to 1 is that the query planner will behave more like the PostgreSQL 7.3 query planner, which some users might find useful for backward compatibility reasons. Setting this variable to a value between 1 and from_collapse_limit might be useful to trade off planning time against the quality of the chosen plan (higher values produce better plans).
+The planner will rewrite explicit JOIN constructs (except FULL JOINs) into lists of FROM items whenever a list of no more than this many items would result. Smaller values reduce planning time but may yield inferior query plans. By default, this variable is set the same as from_collapse_limit, which is appropriate for most uses. Setting it to 1 prevents any reordering of explicit JOINs. Thus, the explicit join order specified in the query will be the actual order in which the relations are joined. The query planner does not always choose the optimal join order; advanced users may elect to temporarily set this variable to 1, and then specify the join order they desire explicitly. For more information see Section 13.3.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the language in which messages are displayed. Acceptable values are system-dependent; see Section 21.1 for more information. If this variable is set to the empty string (which is the default) then the value is inherited from the execution environment of the server in a system-dependent way. On some systems, this locale category does not exist. Setting this variable will still work, but there will be no effect. Also, there is a chance that no translated messages for the desired language exist. In that case you will continue to see the English messages.
+Sets the language in which messages are displayed. Acceptable values are system-dependent; see Section 21.1 for more information. If this variable is set to the empty string (which is the default) then the value is inherited from the execution environment of the server in a system-dependent way. On some systems, this locale category does not exist. Setting this variable will still work, but there will be no effect. Also, there is a chance that no translated messages for the desired language exist. In that case you will continue to see the English messages. Only superusers can change this setting, because it affects the messages sent to the server log as well as to the client.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+This variable specifies one or more shared libraries that are to be preloaded at connection start. If more than one library is to be loaded, separate their names with commas. This parameter cannot be changed after the start of a particular session. Because this is not a superuser-only option, 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. There is no performance advantage to loading a library at session start rather than when it is first used. Rather, 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, debugging could be enabled for all sessions under a given user name by setting this parameter with ALTER USER SET. If a specified library is not found, the connection attempt will fail. Every PostgreSQL-supported library has a "magic block" that is checked to guarantee compatibility. For this reason, non-PostgreSQL libraries cannot be loaded in this way.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This outputs a line to the server log detailing each successful connection. This is off by default, although it is probably very useful. 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. This option can only be set at server start or in the postgresql.conf configuration file.
+This outputs a line to the server log detailing each successful connection. This is off by default, although it is probably very useful. 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. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-PostgreSQL supports several methods for logging server messages, including stderr and syslog. On Windows, eventlog is also supported. Set this option to a list of desired log destinations separated by commas. The default is to log to stderr only. This option can be set at server start or in the postgresql.conf configuration file.
+PostgreSQL supports several methods for logging server messages, including stderr 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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When redirect_stderr is enabled, this option determines the directory in which log files will be created. It may be specified as an absolute path, or relative to the cluster data directory. This option can be set at server start or in the postgresql.conf configuration file.
+When redirect_stderr is enabled, this parameter determines the directory in which log files will be created. It may 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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This outputs a line in the server log similar to log_connections but at session termination, and includes the duration of the session. This is off by default. This option can be set at server start or in the postgresql.conf configuration file.
+This outputs a line in the server log similar to log_connections but at session termination, and includes the duration of the session. This is off by default. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Causes the duration of every completed statement which satisfies log_statement to be logged. When using this option, 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. The default is off. Only superusers can change this setting.
+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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When redirect_stderr is enabled, this option sets the file names of the created log files. The value is treated as a strftime pattern, so %-escapes can be used to specify time-varying file names. If no %-escapes are present, PostgreSQL will append the epoch of the new log file's open time. For example, if log_filename were server_log, then the chosen file name would be server_log.1093827753 for a log starting at Sun Aug 29 19:02:33 2004 MST. This option can be set at server start or in the postgresql.conf configuration file.
+When redirect_stderr is enabled, this parameter sets the file names of the created log files. The value is treated as a strftime pattern, so %-escapes can be used to specify time-varying file names. If no %-escapes are present, PostgreSQL will append the epoch of the new log file's open time. For example, if log_filename were server_log, then the chosen file name would be server_log.1093827753 for a log starting at Sun Aug 29 19:02:33 2004 MST. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-By default, connection log messages only show the IP address of the connecting host. Turning on this option causes logging of the host name as well. Note that depending on your host name resolution setup this might impose a non-negligible performance penalty. This option can be set at server start or in the postgresql.conf file.
+By default, connection log messages only show the IP address of the connecting host. Turning on this parameter causes logging of the host name as well. Note that depending on your host name resolution setup this might impose a non-negligible performance penalty. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This is a printf-style string that is output at the beginning of each log line. The default is an empty string. Each recognized escape is replaced as outlined below - anything else that looks like an escape is ignored. Other characters are copied straight to the log line. Some escapes are only recognized by session processes, and do not apply to background processes such as the postmaster. Syslog produces its own time stamp and process ID information, so you probably do not want to use those escapes if you are using syslog. This option can be set at server start or in the postgresql.conf configuration file. Escape Effect Session only %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 (no milliseconds) no %m Time stamp with milliseconds no %i Command tag: This is the command that generated the log line. yes %c Session ID: A unique identifier for each session. It is 2 4-byte hexadecimal numbers (without leading zeros) separated by a dot. The numbers are the session start time and the process ID, so this can also be used as a space saving way of printing these items. yes %l Number of the log line for each process, starting at 1 no %s Session start time stamp yes %x Transaction ID yes %q Does not produce any output, but tells non-session processes to stop at this point in the string. Ignored by session processes. no %% Literal % no
+This is a printf-style string that is output at the beginning of each log line. The default is an empty string. Each recognized escape is replaced as outlined below - anything else that looks like an escape is ignored. Other characters are copied straight to the log line. Some escapes are only recognized by session processes, and do not apply to background processes such as the main server process. Syslog produces its own time stamp and process ID information, so you probably do not want to use those escapes if you are using syslog. This parameter can only be set in the postgresql.conf file or on the server command line. Escape Effect Session only %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 (no milliseconds, no timezone on Windows) no %m Time stamp with milliseconds no %i Command tag: This is the command that generated the log line. yes %c Session ID: A unique identifier for each session. It is 2 4-byte hexadecimal numbers (without leading zeros) separated by a dot. The numbers are the session start time and the process ID, so this can also be used as a space saving way of printing these items. yes %l Number of the log line for each process, starting at 1 no %s Session start time stamp yes %x Transaction ID yes %q Does not produce any output, but tells non-session processes to stop at this point in the string. Ignored by session processes. no %% Literal % no

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Logs the statement and its duration on a single log line if its duration is greater than or equal to the specified number of milliseconds. Setting this to zero will print all statements and their durations. Minus-one (the default) disables the feature. For example, if you set it to 250 then all SQL statements that run 250ms or longer will be logged. Enabling this option can be useful in tracking down unoptimized queries in your applications. This setting is independent of log_statement and log_duration. Only superusers can change this setting.
+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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Controls whether or not the SQL statement that causes an error condition will also be recorded in the server log. All SQL statements that cause an error of the specified level or higher are logged. The default is PANIC (effectively turning this feature off for normal use). Valid values are DEBUG5, DEBUG4, DEBUG3, DEBUG2, DEBUG1, INFO, NOTICE, WARNING, ERROR, FATAL, and PANIC. For example, if you set this to ERROR then all SQL statements causing errors, fatal errors, or panics will be logged. Enabling this option can be helpful in tracking down the source of any errors that appear in the server log. Only superusers can change this setting.
+Controls whether or not the SQL statement that causes an error condition will be recorded in the server log. The current SQL statement is included in the log entry for any message of the specified severity or higher. Valid values are DEBUG5, DEBUG4, DEBUG3, DEBUG2, DEBUG1, INFO, NOTICE, WARNING, ERROR, FATAL, and PANIC. The default is ERROR, which means statements causing errors, fatal errors, or panics will be logged. To effectively turn off logging of failing statements, set this parameter to PANIC. Only superusers can change this setting.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When redirect_stderr is enabled, this option determines the maximum lifetime of an individual log file. After this many minutes have elapsed, a new log file will be created. Set to zero to disable time-based creation of new log files. This option can be set at server start or in the postgresql.conf configuration file.
+When redirect_stderr is enabled, this parameter determines the maximum lifetime of an individual log file. After this many minutes have elapsed, a new log file will be created. Set to zero to disable time-based creation of new log files. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When redirect_stderr is enabled, this option determines the maximum size of an individual log file. After this many kilobytes have been emitted into a log file, a new log file will be created. Set to zero to disable size-based creation of new log files. This option can be set at server start or in the postgresql.conf configuration file.
+When redirect_stderr is enabled, this parameter determines the maximum size of an individual log file. After this many kilobytes have been emitted into a log file, a new log file will be created. Set to zero to disable size-based creation of new log files. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Controls which SQL statements are logged. Valid values are none, ddl, mod, and all. ddl logs all data definition commands like CREATE, ALTER, and DROP commands. mod logs all ddl statements, plus INSERT, UPDATE, DELETE, TRUNCATE, and COPY FROM. PREPARE and EXPLAIN ANALYZE statements are also logged if their contained command is of an appropriate type. The default is none. Only superusers can change this setting. Note: The EXECUTE statement is not considered a ddl or mod statement. Statements that generate syntax errors are not logged. Set log_min_error_statement to error to log such statements. When a function is defined in the PL/pgSQLserver-side language, any queries executed by the function will only be logged the first time that the function is invoked in a particular session. This is because PL/pgSQL keeps a cache of the query plans produced for the SQL statements in the function.
+Controls which SQL statements are logged. Valid values are none, ddl, mod, and all. 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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When redirect_stderr is enabled, this option will cause PostgreSQL to truncate (overwrite), rather than append to, any existing log file of the same name. However, truncation will occur only when a new file is being opened due to time-based rotation, not during server startup or size-based rotation. When off, pre-existing files will be appended to in all cases. For example, using this option in combination with a log_filename like postgresql-%H.log would result in generating twenty-four hourly log files and then cyclically overwriting them. This option can be set at server start or in the postgresql.conf configuration file. Example: To keep 7 days of logs, one log file per day named server_log.Mon, server_log.Tue, etc, and automatically overwrite last week's log with this week's log, set log_filename to server_log.%a, log_truncate_on_rotation to on, and log_rotation_age to 1440. Example: To keep 24 hours of logs, one log file per hour, but also rotate sooner if the log file size exceeds 1GB, set log_filename to server_log.%H%M, log_truncate_on_rotation to on, log_rotation_age to 60, and log_rotation_size to 1000000. Including %M in log_filename allows any size-driven rotations that may occur to select a file name different from the hour's initial file name.
+When redirect_stderr is enabled, this parameter will cause PostgreSQL to truncate (overwrite), rather than append to, any existing log file of the same name. However, truncation will occur only when a new file is being opened due to time-based rotation, not during server startup or size-based rotation. When off, pre-existing files will be appended to in all cases. For example, using this setting in combination with a log_filename like postgresql-%H.log would result in generating twenty-four hourly log files and then cyclically overwriting them. This parameter can only be set in the postgresql.conf file or on the server command line. Example: To keep 7 days of logs, one log file per day named server_log.Mon, server_log.Tue, etc, and automatically overwrite last week's log with this week's log, set log_filename to server_log.%a, log_truncate_on_rotation to on, and log_rotation_age to 1440. Example: To keep 24 hours of logs, one log file per hour, but also rotate sooner if the log file size exceeds 1GB, set log_filename to server_log.%H%M, log_truncate_on_rotation to on, log_rotation_age to 60, and log_rotation_size to 1000000. Including %M in log_filename allows any size-driven rotations that may occur to select a file name different from the hour's initial file name.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the maximum amount of memory to be used in maintenance operations, such as VACUUM, CREATE INDEX, and ALTER TABLE ADD FOREIGN KEY. The value is specified in kilobytes, and defaults to 16384 kilobytes (16 MB). Since only one of these operations can be executed at a time by a database session, and an installation normally doesn't have very many of them happening concurrently, it's safe to set this value significantly larger than work_mem. Larger settings may improve performance for vacuuming and for restoring database dumps.
+Specifies the maximum amount of memory to be used in maintenance operations, such as VACUUM, CREATE INDEX, and ALTER TABLE ADD FOREIGN KEY. It defaults to 16 megabytes (16MB). Since only one of these operations can be executed at a time by a database session, and an installation normally doesn't have many of them running concurrently, it's safe to set this value significantly larger than work_mem. Larger settings may improve performance for vacuuming and for restoring database dumps.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Determines the maximum number of concurrent connections to the database server. The default is typically 100, but may be less if your kernel settings will not support it (as determined during initdb). This parameter can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory or semaphores than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.
+Determines the maximum number of concurrent connections to the database server. The default is typically 100 connections, but may be less if your kernel settings will not support it (as determined during initdb). This parameter can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory or semaphores than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the maximum number of simultaneously open files allowed to each server subprocess. The default is 1000. 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 really support when a large number of processes all try to open that many files. If you find yourself seeing "Too many open files" failures, try reducing this setting. This option 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 really support when a large number of 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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the maximum number of disk pages for which free space will be tracked in the shared free-space map. Six bytes of shared memory are consumed for each page slot. This setting must be more than 16 * max_fsm_relations. The default is 20000. This option can only be set at server start.
+Sets the maximum number of disk pages for which free space will be tracked in the shared free-space map. Six bytes of shared memory are consumed for each page slot. This setting must be at least 16 * max_fsm_relations. The default is chosen by initdb depending on the amount of available memory, and can range from 20k to 200k pages. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the maximum number of relations (tables and indexes) for which free space will be tracked in the shared free-space map. Roughly seventy bytes of shared memory are consumed for each slot. The default is 1000. This option can only be set at server start.
+Sets the maximum number of relations (tables and indexes) for which free space will be tracked in the shared free-space map. Roughly seventy bytes of shared memory are consumed for each slot. The default is one thousand relations. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Reports the maximum number of function arguments. It is determined by the value of FUNC_MAX_ARGS when building the server. The default value is 100.
+Reports the maximum number of function arguments. It is determined by the value of FUNC_MAX_ARGS when building the server. The default value is 100 arguments.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Reports the maximum identifier length. It is determined as one less than the value of NAMEDATALEN when building the server. The default value of NAMEDATALEN is 64; therefore the default max_identifier_length is 63.
+Reports the maximum identifier length. It is determined as one less than the value of NAMEDATALEN when building the server. The default value of NAMEDATALEN is 64; therefore the default max_identifier_length is 63 bytes.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Reports the maximum number of index keys. It is determined by the value of INDEX_MAX_KEYS when building the server. The default value is 32.
+Reports the maximum number of index keys. It is determined by the value of INDEX_MAX_KEYS when building the server. The default value is 32 keys.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-The shared lock table is created with room to describe locks on max_locks_per_transaction * (max_connections + max_prepared_transactions) objects; hence, no more than this many distinct objects can be locked at any one time. (Thus, this parameter's name may be confusing: it is not a hard limit on the number of locks taken by any one transaction, but rather a maximum average value.) The default, 64, has historically proven sufficient, but you might need to raise this value if you have clients that touch many different tables in a single transaction. This option can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.
+The shared lock table is created to track locks on max_locks_per_transaction * (max_connections + max_prepared_transactions) objects (e.g. tables); hence, no more than this many distinct objects can be locked at any one time. This parameter controls the average number of object locks allocated for each transaction; individual transactions can lock more objects as long as the locks of all transactions fit in the lock table. This is not the number of rows that can be locked; that value is unlimited. The default, 64, has historically proven sufficient, but you might need to raise this value if you have clients that touch many different tables in a single transaction. This parameter can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the maximum number of transactions that can be in the "prepared" state simultaneously (see PREPARE TRANSACTION). Setting this parameter to zero disables the prepared-transaction feature. The default is 5. This option can only be set at server start. If you are not using prepared transactions, this parameter may as well be set to zero. If you are using them, you will probably want max_prepared_transactions to be at least as large as max_connections, to avoid unwanted failures at the prepare step. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.
+Sets the maximum number of transactions that can be in the "prepared" state simultaneously (see PREPARE TRANSACTION). Setting this parameter to zero disables the prepared-transaction feature. The default is five transactions. This parameter can only be set at server start. If you are not using prepared transactions, this parameter may as well be set to zero. If you are using them, you will probably want max_prepared_transactions to be at least as large as max_connections, to avoid unwanted failures at the prepare step. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the maximum safe depth of the server's execution stack. The ideal setting for this parameter is the actual stack size limit enforced by the kernel (as set by ulimit -s or local equivalent), less a safety margin of a megabyte or so. The safety margin is needed because the stack depth is not checked in every routine in the server, but only in key potentially-recursive routines such as expression evaluation. Setting the parameter higher than the actual kernel limit will mean that a runaway recursive function can crash an individual backend process. The default setting is 2048 KB (two megabytes), which is conservatively small and unlikely to risk crashes. However, it may be too small to allow execution of complex functions.
+Specifies the maximum safe depth of the server's execution stack. The ideal setting for this parameter is the actual stack size limit enforced by the kernel (as set by ulimit -s or local equivalent), less a safety margin of a megabyte or so. The safety margin is needed because the stack depth is not checked in every routine in the server, but only in key potentially-recursive routines such as expression evaluation. The default setting is two megabytes (2MB), which is conservatively small and unlikely to risk crashes. However, it may be too small to allow execution of complex functions. Only superusers can change this setting. Setting max_stack_depth higher than the actual kernel limit will mean that a runaway recursive function can crash an individual backend process. On platforms where PostgreSQL can determine the kernel limit, it will not let you set this variable to an unsafe value. However, not all platforms provide the information, so caution is recommended in selecting a value.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When a password is specified in CREATE USER or ALTER USER without writing either ENCRYPTED or UNENCRYPTED, this option determines whether the password is to be encrypted. The default is on (encrypt the password).
+When a password is specified in CREATE USER or ALTER USER without writing either ENCRYPTED or UNENCRYPTED, this parameter determines whether the password is to be encrypted. The default is on (encrypt the password).

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+If nonzero, a delay of this many seconds occurs when a new server process is started, after it conducts the authentication procedure. This is intended to give an opportunity to attach to the server process with a debugger. This parameter cannot be changed after session start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-If nonzero, a delay of this many seconds occurs just after a new server process is forked, before it conducts the authentication process. This is intended to give an opportunity to attach to the server process with a debugger to trace down misbehavior in authentication.
+If nonzero, a delay of this many seconds occurs just after a new server process is forked, before it conducts the authentication procedure. This is intended to give an opportunity to attach to the server process with a debugger to trace down misbehavior in authentication. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1,3 +0,0 @@
-
-
-This variable specifies one or more shared libraries that are to be preloaded at server start. A parameterless initialization function can optionally be called for each library. To specify that, add a colon and the name of the initialization function after the library name. For example '$libdir/mylib:mylib_init' would cause mylib to be preloaded and mylib_init to be executed. If more than one library is to be loaded, separate their names with commas. If a specified library or initialization function is not found, the server will fail to start. PostgreSQL procedural language libraries may be preloaded in this way, typically by using the syntax '$libdir/plXXX:plXXX_init' where XXX is pgsql, perl, tcl, or python. By preloading a shared library (and initializing it if applicable), the library startup time is avoided when the library is first used. However, the time to start each new server process may increase slightly, even if that process never uses the library. So this option is recommended only for libraries that will be used in most sessions.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the planner's estimate of the cost of a nonsequentially fetched disk page. This is measured as a multiple of the cost of a sequential page fetch. A higher value makes it more likely a sequential scan will be used, a lower value makes it more likely an index scan will be used. The default is four.
+Sets the planner's estimate of the cost of a non-sequentially-fetched disk page. The default is 4.0. 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. 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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This option allows messages sent to stderr to be captured and redirected into log files. This option, in combination with logging to stderr, is often more useful than logging to syslog, since some types of messages may not appear in syslog output (a common example is dynamic-linker failure messages). This option can only be set at server start.
+This parameter allows messages sent to stderr to be captured and redirected into log files. This method, in combination with logging to stderr, is often more useful than logging to syslog, since some types of messages may not appear in syslog output (a common example is dynamic-linker failure messages). This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This variable specifies the order in which schemas are searched when an object (table, data type, function, etc.) is referenced by a simple name with no schema component. When there are objects of identical names in different schemas, the one found first in the search path is used. An object that is not in any of the schemas in the search path can only be referenced by specifying its containing schema with a qualified (dotted) name. The value for search_path has to be a comma-separated list of schema names. If one of the list items is the special value $user, then the schema having the name returned by SESSION_USER is substituted, if there is such a schema. (If not, $user is ignored.) The system catalog schema, pg_catalog, is always searched, whether it is mentioned in the path or not. If it is mentioned in the path then it will be searched in the specified order. If pg_catalog is not in the path then it will be searched before searching any of the path items. Likewise, the current session's temporary-table schema, pg_temp_nnn, is always searched if it exists. It can be explicitly listed in the path by using the alias pg_temp. If it is not listed in the path then it is searched first (before even pg_catalog). However, the temporary schema is only searched for relation (table, view, sequence, etc) and data type names. It will never be searched for function or operator names. When objects are created without specifying a particular target schema, they will be placed in the first schema listed in the search path. An error is reported if the search path is empty. The default value for this parameter is '$user, public' (where the second part will be ignored if there is no schema named public). This supports shared use of a database (where no users have private schemas, and all share use of public), private per-user schemas, and combinations of these. Other effects can be obtained by altering the default search path setting, either globally or per-user. The current effective value of the search path can be examined via the SQL function current_schemas(). This is not quite the same as examining the value of search_path, since current_schemas() shows how the requests appearing in search_path were resolved. For more information on schema handling, see Section 5.7.
+This variable specifies the order in which schemas are searched when an object (table, data type, function, etc.) is referenced by a simple name with no schema component. When there are objects of identical names in different schemas, the one found first in the search path is used. An object that is not in any of the schemas in the search path can only be referenced by specifying its containing schema with a qualified (dotted) name. The value for search_path has to be a comma-separated list of schema names. If one of the list items is the special value $user, then the schema having the name returned by SESSION_USER is substituted, if there is such a schema. (If not, $user is ignored.) The system catalog schema, pg_catalog, is always searched, whether it is mentioned in the path or not. If it is mentioned in the path then it will be searched in the specified order. If pg_catalog is not in the path then it will be searched before searching any of the path items. Likewise, the current session's temporary-table schema, pg_temp_nnn, is always searched if it exists. It can be explicitly listed in the path by using the alias pg_temp. If it is not listed in the path then it is searched first (before even pg_catalog). However, the temporary schema is only searched for relation (table, view, sequence, etc) and data type names. It will never be searched for function or operator names. When objects are created without specifying a particular target schema, they will be placed in the first schema listed in the search path. An error is reported if the search path is empty. The default value for this parameter is '"$user", public' (where the second part will be ignored if there is no schema named public). This supports shared use of a database (where no users have private schemas, and all share use of public), private per-user schemas, and combinations of these. Other effects can be obtained by altering the default search path setting, either globally or per-user. The current effective value of the search path can be examined via the SQL function current_schemas(). This is not quite the same as examining the value of search_path, since current_schemas() shows how the requests appearing in search_path were resolved. For more information on schema handling, see Section 5.7.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Sets the planner's estimate of the cost of a disk page fetch that is part of a series of sequential fetches. The default is 1.0.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Reports the version number of the server as an integer. It is determined by the value of PG_VERSION_NUM when building the server.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the number of shared memory buffers used by the database server. The default is typically 1000, but may be less if your kernel settings will not support it (as determined during initdb). Each buffer is 8192 bytes, unless a different value of BLCKSZ was chosen when building the server. This setting must be at least 16, as well as at least twice the value of max_connections; however, settings significantly higher than the minimum are usually needed for good performance. Values of a few thousand are recommended for production installations. This option can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.
+Sets the amount of memory the database server uses for shared memory buffers. The default is typically 32 megabytes (32MB), but may be less if your kernel settings will not support it (as determined during initdb). This setting must be at least 128 kilobytes and at least 16 kilobytes times max_connections. (Non-default values of BLCKSZ change the minimum.) However, settings significantly higher than the minimum are usually needed for good performance. Several tens of megabytes are recommended for production installations. This parameter can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+This variable specifies one or more shared libraries that are to be preloaded at server start. If more than one library is to be loaded, separate their names with commas. For example, '$libdir/mylib' would cause mylib.so (or on some platforms, mylib.sl) to be preloaded from the installation's standard library directory. This parameter can only be set at server start. PostgreSQL procedural language libraries can be preloaded in this way, typically by using the syntax '$libdir/plXXX' where XXX is pgsql, perl, tcl, or python. 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 may 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. 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 because some shared libraries may need to perform certain operations that only take place at postmaster start (for example, a shared library may need to reserve lightweight locks or shared memory and you can't do that after the postmaster has started). If a specified library is not found, the server will fail to start. Every PostgreSQL-supported library has a "magic block" that is checked to guarantee compatibility. For this reason, non-PostgreSQL libraries cannot be loaded in this way.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Runs the server silently. If this option is set, the server will automatically run in background and any controlling terminals are disassociated (same effect as postmaster's -S option). The server's standard output and standard error are redirected to /dev/null, so any messages sent to them will be lost. Unless syslog logging is selected or redirect_stderr is enabled, using this option is discouraged because it makes it impossible to see error messages.
+Runs the server silently. If this parameter is set, the server will automatically run in background and any controlling terminals are disassociated. The server's standard output and standard error are redirected to /dev/null, so any messages sent to them will be lost. Unless syslog logging is selected or redirect_stderr is enabled, using this parameter is discouraged because it makes it impossible to see error messages. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-This controls the inheritance semantics, in particular whether subtables are included by various commands by default. They were not included in versions prior to 7.1. If you need the old behavior you can set this variable to off, but in the long run you are encouraged to change your applications to use the ONLY key word to exclude subtables. See Section 5.8 for more information about inheritance.
+This controls the inheritance semantics. If turned off, subtables are not included by various commands by default; basically an implied ONLY key word. This was added for compatibility with releases prior to 7.1. See Section 5.8 for more information.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Reports whether ordinary string literals ('...') treat backslashes literally, as specified in the SQL standard. The value is currently always off, indicating that backslashes are treated as escapes. It is planned that this will change to on in a future PostgreSQL release when string literal syntax changes to meet the standard. Applications may check this parameter to determine how string literals will be processed. The presence of this parameter can also be taken as an indication that the escape string syntax (E'...') is supported.
+This controls whether ordinary string literals ('...') treat backslashes literally, as specified in the SQL standard. The default is currently off, causing PostgreSQL to have its historical behavior of treating backslashes as escape characters. The default will change to on in a future release to improve compatibility with the standard. Applications may check this parameter to determine how string literals will be processed. The presence of this parameter can also be taken as an indication that the escape string syntax (E'...') is supported. Escape string syntax should be used if an application desires backslashes to be treated as escape characters.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Abort any statement that takes over the specified number of milliseconds. If log_min_error_statement is set to ERROR or lower, the statement that timed out will also be logged. A value of zero (the default) turns off the limitation.
+Abort any statement that takes over the specified number of milliseconds, starting from the time the command arrives at the server from the client. If log_min_error_statement is set to ERROR or lower, the statement that timed out will also be logged. A value of zero (the default) turns off the limitation.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Enables the collection of block-level statistics on database activity. This option is disabled by default. If this option is enabled, the data that is produced can be accessed via the pg_stat and pg_statio family of system views; refer to Chapter 24 for more information.
+Enables the collection of block-level statistics on database activity. This parameter is off by default. Only superusers can change this setting.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Enables the collection of statistics on the currently executing command of each session, along with the time at which that command began execution. This option is off 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. This data can be accessed via the pg_stat_activity system view; refer to Chapter 24 for more information.
+Enables the collection of information on the currently executing command of each session, along with the time at which 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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-If on, collected statistics are zeroed out whenever the server is restarted. If off, statistics are accumulated across server restarts. The default is off. This option can only be set at server start.
+If on, collected block-level and row-level statistics are zeroed out whenever the server is restarted. If off, statistics are accumulated across server restarts. This parameter is off by default. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Enables the collection of row-level statistics on database activity. This option is disabled by default. If this option is enabled, the data that is produced can be accessed via the pg_stat and pg_statio family of system views; refer to Chapter 24 for more information.
+Enables the collection of row-level statistics on database activity. This parameter is off by default. Only superusers can change this setting.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Controls whether the server should start the statistics-collection subprocess. This is on by default, but may be turned off if you know you have no interest in collecting statistics. This option can only be set at server start.
+Controls whether the server should start the statistics-collection subprocess. This is on by default, but may be turned off if you know you have no interest in collecting statistics or running autovacuum. This parameter can only be set at server start, because the collection subprocess cannot be started or stopped on-the-fly. (However, the extent to which statistics are actually gathered can be changed while the server is running, so long as the subprocess exists.)

--- 8.1
+++ 8.2
@@ -1 +1 @@
-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. The default value is 2. 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. 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.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When logging to syslog is enabled, this option determines the syslog "facility" to be used. You may 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 option can be set at server start or in the postgresql.conf configuration file.
+When logging to syslog is enabled, this parameter determines the syslog "facility" to be used. You may 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. This parameter is unavailable unless the server is compiled with support for syslog.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When logging to syslog is enabled, this option determines the program name used to identify PostgreSQL messages in syslog logs. The default is postgres. This option can be set at server start or in the postgresql.conf configuration file.
+When logging to syslog is enabled, this parameter determines the program name used to identify PostgreSQL messages in syslog logs. The default is postgres. This parameter can only be set in the postgresql.conf file or on the server command line. This parameter is unavailable unless the server is compiled with support for syslog.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-On systems that support the TCP_KEEPCNT socket option, specifies how many keepalives may be lost before the connection is considered dead. A value of 0 uses the system default. If TCP_KEEPCNT is not supported, this parameter must be 0. This option is ignored for connections made via a Unix-domain socket.
+On systems that support the TCP_KEEPCNT socket option, specifies how many keepalives may be lost before the connection is considered dead. A value of zero uses the system default. If TCP_KEEPCNT is not supported, this parameter must be zero. This parameter is ignored for connections made via a Unix-domain socket.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-On systems that support the TCP_KEEPIDLE socket option, specifies the number of seconds between sending keepalives on an otherwise idle connection. A value of 0 uses the system default. If TCP_KEEPIDLE is not supported, this parameter must be 0. This option is ignored for connections made via a Unix-domain socket.
+On systems that support the TCP_KEEPIDLE socket option, specifies the number of seconds between sending keepalives on an otherwise idle connection. A value of zero uses the system default. If TCP_KEEPIDLE is not supported, this parameter must be zero. This parameter is ignored for connections made via a Unix-domain socket.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-On systems that support the TCP_KEEPINTVL socket option, specifies how long, in seconds, to wait for a response to a keepalive before retransmitting. A value of 0 uses the system default. If TCP_KEEPINTVL is not supported, this parameter must be 0. This option is ignored for connections made via a Unix-domain socket.
+On systems that support the TCP_KEEPINTVL socket option, specifies how long, in seconds, to wait for a response to a keepalive before retransmitting. A value of zero uses the system default. If TCP_KEEPINTVL is not supported, this parameter must be zero. This parameter is ignored for connections made via a Unix-domain socket.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the maximum number of temporary buffers used by each database session. These are session-local buffers used only for access to temporary tables. The default is 1000. The setting can be changed within individual sessions, but only up until the first use of temporary tables within a session; subsequent attempts to change the value will have no effect on that session. A session will allocate temporary buffers as needed up to the limit given by temp_buffers. The cost of setting a large value in sessions that do not actually need a lot of temporary buffers is only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed for it (or in general, BLCKSZ bytes).
+Sets the maximum number of temporary buffers used by each database session. These are session-local buffers used only for access to temporary tables. The default is eight megabytes (8MB). The setting can be changed within individual sessions, but only up until the first use of temporary tables within a session; subsequent attempts to change the value will have no effect on that session. A session will allocate temporary buffers as needed up to the limit given by temp_buffers. The cost of setting a large value in sessions that do not actually need a lot of temporary buffers is only a buffer descriptor, or about 64 bytes, per increment in temp_buffers. However if a buffer is actually used an additional 8192 bytes will be consumed for it (or in general, BLCKSZ bytes).

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Sets the collection of time zone abbreviations that will be accepted by the server for datetime input. The default is 'Default', which is a collection that works in most of the world; there are also 'Australia' and 'India', and other collections can be defined for a particular installation. See Appendix B for more information.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-If on, emit information about resource usage during sort operations. This option is only available if the TRACE_SORT macro was defined when PostgreSQL was compiled. (However, TRACE_SORT is currently defined by default.)
+If on, emit information about resource usage during sort operations. This parameter is only available if the TRACE_SORT macro was defined when PostgreSQL was compiled. (However, TRACE_SORT is currently defined by default.)

--- 8.1
+++ 8.2
@@ -1 +1 @@
-When on, expressions of the form expr = NULL (or NULL = expr) are treated as expr IS NULL, that is, they return true if expr evaluates to the null value, and false otherwise. The correct SQL-spec-compliant behavior of expr = NULL is to always return null (unknown). Therefore this option defaults to off. However, filtered forms in Microsoft Access generate queries that appear to use expr = NULL to test for null values, so if you use that interface to access the database you might want to turn this option on. Since expressions of the form expr = NULL always return the null value (using the correct interpretation) they are not very useful and do not appear often in normal applications, so this option does little harm in practice. But new users are frequently confused about the semantics of expressions involving null values, so this option is not on by default. Note that this option only affects the exact form = NULL, not other comparison operators or other expressions that are computationally equivalent to some expression involving the equals operator (such as IN). Thus, this option is not a general fix for bad programming. Refer to Section 9.2 for related information.
+When on, expressions of the form expr = NULL (or NULL = expr) are treated as expr IS NULL, that is, they return true if expr evaluates to the null value, and false otherwise. The correct SQL-spec-compliant behavior of expr = NULL is to always return null (unknown). Therefore this parameter defaults to off. However, filtered forms in Microsoft Access generate queries that appear to use expr = NULL to test for null values, so if you use that interface to access the database you might want to turn this option on. Since expressions of the form expr = NULL always return the null value (using the correct interpretation) they are not very useful and do not appear often in normal applications, so this option does little harm in practice. But new users are frequently confused about the semantics of expressions involving null values, so this option is not on by default. Note that this option only affects the exact form = NULL, not other comparison operators or other expressions that are computationally equivalent to some expression involving the equals operator (such as IN). Thus, this option is not a general fix for bad programming. Refer to Section 9.2 for related information.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the owning group of the Unix-domain socket. (The owning user of the socket is always the user that starts the server.) In combination with the option unix_socket_permissions this can be used as an additional access control mechanism for Unix-domain connections. By default this is the empty string, which uses the default group for the current user. This option can only be set at server start.
+Sets the owning group of the Unix-domain socket. (The owning user of the socket is always the user that starts the server.) In combination with the parameter unix_socket_permissions this can be used as an additional access control mechanism for Unix-domain connections. By default this is the empty string, which selects the default group for the current user. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Sets the access permissions of the Unix-domain socket. Unix-domain sockets use the usual Unix file system permission set. The option value is expected to be a numeric mode specification in the form accepted by the chmod and umask system calls. (To use the customary octal format the number must start with a 0 (zero).) The default permissions are 0777, meaning anyone can connect. Reasonable alternatives are 0770 (only user and group, see also unix_socket_group) and 0700 (only user). (Note that for a Unix-domain socket, only write permission matters and so there is no point in setting or revoking read or execute permissions.) This access control mechanism is independent of the one described in Chapter 20. This option can only be set at server start.
+Sets the access permissions of the Unix-domain socket. Unix-domain sockets use the usual Unix file system permission set. The parameter value is expected to be a numeric mode specification in the form accepted by the chmod and umask system calls. (To use the customary octal format the number must start with a 0 (zero).) The default permissions are 0777, meaning anyone can connect. Reasonable alternatives are 0770 (only user and group, see also unix_socket_group) and 0700 (only user). (Note that for a Unix-domain socket, only write permission matters and so there is no point in setting or revoking read or execute permissions.) This access control mechanism is independent of the one described in Chapter 20. This parameter can only be set at server start.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Enables updating of the process title every time a new SQL command is received by the server. The process title is typically viewed by the ps command or in Windows using the Process Explorer. Only superusers can change this setting.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-The length of time, in milliseconds, that the process will sleep when the cost limit has been exceeded. The default value is 0, which disables the cost-based vacuum delay feature. Positive values enable cost-based vacuuming. Note that on many systems, the effective resolution of sleep delays is 10 milliseconds; setting vacuum_cost_delay to a value that is not a multiple of 10 may have the same results as setting it to the next higher multiple of 10.
+The length of time, in milliseconds, that the process will sleep when the cost limit has been exceeded. The default value is zero, which disables the cost-based vacuum delay feature. Positive values enable cost-based vacuuming. Note that on many systems, the effective resolution of sleep delays is 10 milliseconds; setting vacuum_cost_delay to a value that is not a multiple of 10 may have the same results as setting it to the next higher multiple of 10.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of the page. The default value is 1.
+The estimated cost for vacuuming a buffer found in the shared buffer cache. It represents the cost to lock the buffer pool, lookup the shared hash table and scan the content of the page. The default value is one.

--- 8.1
+++ 8.2
@@ -0,0 +1,3 @@
+
+
+Specifies the cutoff age (in transactions) that VACUUM should use to decide whether to replace transaction IDs with FrozenXID while scanning a table. The default is 100 million transactions. Although users can set this value anywhere from zero to one billion, VACUUM will silently limit the effective value to half the value of autovacuum_freeze_max_age, so that there is not an unreasonably short time between forced autovacuums. For more information see Section 22.1.3.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Number of disk-page buffers allocated in shared memory for WAL data. The default is 8. The setting need only be large enough to hold the amount of WAL data generated by one typical transaction, since the data is written out to disk at every transaction commit. This option can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.
+The amount of memory used in shared memory for WAL data. The default is 64 kilobytes (64kB). The setting need only be large enough to hold the amount of WAL data generated by one typical transaction, since the data is written out to disk at every transaction commit. This parameter can only be set at server start. Increasing this parameter may cause PostgreSQL to request more System V shared memory than your operating system's default configuration allows. See Section 16.4.1 for information on how to adjust those parameters, if necessary.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-If on, emit WAL-related debugging output. This option is only available if the WAL_DEBUG macro was defined when PostgreSQL was compiled.
+If on, emit WAL-related debugging output. This parameter is only available if the WAL_DEBUG macro was defined when PostgreSQL was compiled.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Method used for forcing WAL updates out to disk. If fsync is off then this setting is irrelevant, since updates will not be forced out at all. Possible values are: open_datasync (write WAL files with open() option O_DSYNC) fdatasync (call fdatasync() at each commit) fsync (call fsync() at each commit) fsync_writethrough (call fsync() at each commit, forcing write-through of any disk write cache) open_sync (write WAL files with open() option O_SYNC) Not all of these choices are available on all platforms. The default is the first method in the above list that is supported by the platform, except that fdatasync is the default on Linux. This option can be set at server start or in the postgresql.conf file.
+Method used for forcing WAL updates out to disk. If fsync is off then this setting is irrelevant, since updates will not be forced out at all. Possible values are: open_datasync (write WAL files with open() option O_DSYNC) fdatasync (call fdatasync() at each commit) fsync (call fsync() at each commit) fsync_writethrough (call fsync() at each commit, forcing write-through of any disk write cache) open_sync (write WAL files with open() option O_SYNC) The open_* options also use O_DIRECT if available. Not all of these choices are available on all platforms. The default is the first method in the above list that is supported by the platform, except that fdatasync is the default on Linux. This parameter can only be set in the postgresql.conf file or on the server command line.

--- 8.1
+++ 8.2
@@ -1 +1 @@
-Specifies the amount of memory to be used by internal sort operations and hash tables before switching to temporary disk files. The value is specified in kilobytes, and defaults to 1024 kilobytes (1 MB). Note that for a complex query, several sort or hash operations might be running in parallel; each one will be allowed to use as much memory as this value specifies before it starts to put data into temporary files. Also, several running sessions could be doing such operations concurrently. So the total memory used could be many times the value of work_mem; it is necessary to keep this fact in mind when choosing the value. Sort operations are used for ORDER BY, DISTINCT, and merge joins. Hash tables are used in hash joins, hash-based aggregation, and hash-based processing of IN subqueries.
+Specifies the amount of memory to be used by internal sort operations and hash tables before switching to temporary disk files. The value is defaults to one megabyte (1MB). Note that for a complex query, several sort or hash operations might be running in parallel; each one will be allowed to use as much memory as this value specifies before it starts to put data into temporary files. Also, several running sessions could be doing such operations concurrently. So the total memory used could be many times the value of work_mem; it is necessary to keep this fact in mind when choosing the value. Sort operations are used for ORDER BY, DISTINCT, and merge joins. Hash tables are used in hash joins, hash-based aggregation, and hash-based processing of IN subqueries.