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ConceptsManual ChaptersPG1823.2.1. Concepts Conceptually, every expression of a collatable data type has a collation. (The built-in collatable data types are text, varchar, and char. User-defined base types can also b…Concepts ConceptsManual ChaptersPG1856.1.2. Concepts The pairs of original (English) messages and their (possibly) translated equivalents are kept in message catalogs, one for each program (although related programs can share …Concepts ConceptsManual ChaptersPG182.2. Concepts PostgreSQL is a relational database management system (RDBMS). That means it is a system for managing data stored in relations. Relation is essentially a mathematical term for …Concepts ConclusionManual ChaptersPG183.7. Conclusion PostgreSQL has many features not touched upon in this tutorial introduction, which has been oriented toward newer users of SQL. These features are discussed in more detail in…Conclusion Concurrency ControlManual ChaptersPG18Chapter 13. Concurrency Control This chapter describes the behavior of the PostgreSQL database system when two or more sessions try to access the same data at the same time. The goals in tha…Concurrency Control Conditional ExpressionsManual ChaptersPG189.18. Conditional Expressions This section describes the SQL-compliant conditional expressions available in PostgreSQL. Tip If your needs go beyond the capabilities of these conditional expr…Conditional Expressions ConditionalsManual ChaptersPG1841.6.4. Conditionals IF and CASE statements let you execute alternative commands based on certain conditions. PL/pgSQL has three forms of IF: IF ... THEN ... END IF IF ... THEN ... ELSE ... …Conditionals ConfigurationManual ChaptersPG18F.12.1. Configuration The dictionary accepts three options: The maxlen parameter specifies the maximum number of digits allowed in an integer word. The default value is 6. The rejectlong par…Configuration ConfigurationManual ChaptersPG18F.13.1. Configuration A dict_xsyn dictionary accepts the following options: matchorig controls whether the original word is accepted by the dictionary. Default is true. matchsynonyms control…Configuration ConfigurationManual ChaptersPG1830.3. Configuration The configuration variable jit determines whether JIT compilation is enabled or disabled. If it is enabled, the configuration variables jit_above_cost, jit_inline_above_c…Configuration ConfigurationManual ChaptersPG18F.26.8.1. Configuration pgcrypto configures itself according to the findings of the main PostgreSQL configure script. The options that affect it are --with-zlib and --with-ssl=openssl. When …Configuration ConfigurationManual ChaptersPG1843.8.1. Configuration This section lists configuration parameters that affect PL/Perl. plperl.on_init (string) # Specifies Perl code to be executed when a Perl interpreter is first initializ…Configuration ConfigurationManual ChaptersPG18F.48.1. Configuration An unaccent dictionary accepts the following options: RULES is the base name of the file containing the list of translation rules. This file must be stored in $SHAREDIR…Configuration Configuration ExampleManual ChaptersPG1812.7. Configuration Example A text search configuration specifies all options necessary to transform a document into a tsvector: the parser to use to break text into tokens, and the dictiona…Configuration Example Configuration ExampleManual ChaptersPG1826.2.6.2. Configuration Example You can create a replication slot like this: postgres=# SELECT * FROM pg_create_physical_replication_slot('node_a_slot'); slot_name | lsn -------------+----- …Configuration Example Configuration ParametersManual ChaptersPG18F.2.1. Configuration Parameters auth_delay.milliseconds (integer) The number of milliseconds to wait before reporting an authentication failure. The default is 0. These parameters must be se…Configuration Parameters Configuration ParametersManual ChaptersPG18F.3.1. Configuration Parameters There are several configuration parameters that control the behavior of auto_explain. Note that the default behavior is to do nothing, so you must set at leas…Configuration Parameters Configuration ParametersManual ChaptersPG18F.4.1. Configuration Parameters basebackup_to_shell.command (string) The command which the server should execute for each archive generated by the backup process. If %f occurs in the command…Configuration Parameters Configuration ParametersManual ChaptersPG18F.5.1. Configuration Parameters basic_archive.archive_directory (string) The directory where the server should copy WAL segment files. This directory must already exist. The default is an em…Configuration Parameters Configuration ParametersManual ChaptersPG18F.20.4. Configuration Parameters isn.weak (boolean) # isn.weak enables the weak input mode, which allows ISN input values to be accepted even when their check digit is wrong. The default is …Configuration Parameters Configuration ParametersManual ChaptersPG18F.24.1. Configuration Parameters passwordcheck.min_password_length (integer) The minimum acceptable password length in bytes. The default is 8. Only superusers can change this setting. Note …Configuration Parameters Configuration ParametersManual ChaptersPG18F.26.7. Configuration Parameters There is one configuration parameter that controls the behavior of pgcrypto. pgcrypto.builtin_crypto_enabled (enum) # pgcrypto.builtin_crypto_enabled determi…Configuration Parameters Configuration ParametersManual ChaptersPG18F.30.2. Configuration Parameters pg_prewarm.autoprewarm (boolean) Controls whether the server should run the autoprewarm worker. This is on by default. This parameter can only be set at serv…Configuration Parameters Configuration ParametersManual ChaptersPG18F.32.4. Configuration Parameters pg_stat_statements.max (integer) pg_stat_statements.max is the maximum number of statements tracked by the module (i.e., the maximum number of rows in the pg…Configuration Parameters Configuration ParametersManual ChaptersPG18F.38.9. Configuration Parameters postgres_fdw.application_name (string) # Specifies a value for application_name configuration parameter used when postgres_fdw establishes a connection to a …Configuration Parameters Configuration ParametersManual ChaptersPG1831.2.8. Configuration Parameters When running the tests against an existing installation, some non-default parameter settings could cause the tests to fail. For example, changing parameters …Configuration Parameters Configuration SettingsManual ChaptersPG1829.12. Configuration Settings Logical replication requires several configuration options to be set. These options are relevant only on one side of the replication.Configuration Settings Configuration Settings FunctionsManual ChaptersPG189.28.1. Configuration Settings Functions Table 9.95 shows the functions available to query and alter run-time configuration parameters. Table 9.95. Configuration Settings Functions Function …Configuration Settings Functions Configuration TestingManual ChaptersPG1812.8.1. Configuration Testing The function ts_debug allows easy testing of a text search configuration. ts_debug([ config regconfig, ] document text, OUT alias text, OUT description text, OU…Configuration Testing ConfigurationsManual ChaptersPG1812.1.3. Configurations The above are all simple text search examples. As mentioned before, full text search functionality includes the ability to do many more things: skip indexing certain w…Configurations configure Complains About a Failed Test ProgramManual ChaptersPG1817.7.4.2. configure Complains About a Failed Test Program If configure complains about a failed test program, this is probably a case of the run-time linker being unable to find some library…configure Complains About a Failed Test Program configure Environment VariablesManual ChaptersPG1817.3.4. configure Environment Variables In addition to the ordinary command-line options described above, configure responds to a number of environment variables. You can specify environment…configure Environment Variables configure OptionsManual ChaptersPG1817.3.3. configure Options configure's command line options are explained below. This list is not exhaustive (use ./configure --help to get one that is). The options not covered here are mean…configure Options Configuring the ColorsManual ChaptersPG18N.2. Configuring the Colors The actual colors to be used are configured using the environment variable PG_COLORS (note plural). The value is a colon-separated list of key=value pairs. The ke…Configuring the Colors ConflictsManual ChaptersPG1829.7. Conflicts Logical replication behaves similarly to normal DML operations in that the data will be updated even if it was changed locally on the subscriber node. If incoming data violat…Conflicts CONNECTManual ChaptersPG18CONNECT CONNECT — establish a database connection Synopsis CONNECT TO connection_target [ AS connection_name ] [ USER connection_user ] CONNECT TO DEFAULT CONNECT connection_user DATABASE co…CONNECT connectbyManual ChaptersPG18F.43.1.5. connectby connectby(text relname, text keyid_fld, text parent_keyid_fld [, text orderby_fld ], text start_with, int max_depth [, text branch_delim ]) The connectby function produce…connectby Connecting to a DatabaseManual ChaptersPG18Connecting to a Database psql is a regular PostgreSQL client application. In order to connect to a database you need to know the name of your target database, the host name and port number o…Connecting to a Database Connecting to the Database ServerManual ChaptersPG1834.2.1. Connecting to the Database Server One connects to a database using the following statement: EXEC SQL CONNECT TO target [AS connection-name] [USER user-name]; The target can be specif…Connecting to the Database Server Connection ManagementManual ChaptersPG18F.38.3. Connection Management postgres_fdw establishes a connection to a foreign server during the first query that uses a foreign table associated with the foreign server. By default this c…Connection Management