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DescriptionManual ChaptersPG18Description The SET command changes run-time configuration parameters. Many of the run-time parameters listed in Chapter 19 can be changed on-the-fly with SET. (Some parameters can only be c…Description DescriptionManual ChaptersPG18Description SHOW will display the current setting of run-time parameters. These variables can be set using the SET statement, by editing the postgresql.conf configuration file, through the P…Description DescriptionManual ChaptersPG18Description This command begins a new transaction block. If the isolation level, read/write mode, or deferrable mode is specified, the new transaction has those characteristics, as if SET TR…Description DescriptionManual ChaptersPG18Description TRUNCATE quickly removes all rows from a set of tables. It has the same effect as an unqualified DELETE on each table, but since it does not actually scan the tables it is faster…Description DescriptionManual ChaptersPG18Description UNLISTEN is used to remove an existing registration for NOTIFY events. UNLISTEN cancels any existing registration of the current PostgreSQL session as a listener on the notificat…Description DescriptionManual ChaptersPG18Description UPDATE changes the values of the specified columns in all rows that satisfy the condition. Only the columns to be modified need be mentioned in the SET clause; columns not explic…Description DescriptionManual ChaptersPG18Description VACUUM reclaims storage occupied by dead tuples. In normal PostgreSQL operation, tuples that are deleted or obsoleted by an update are not physically removed from their table; th…Description DescriptionManual ChaptersPG18Description VALUES computes a row value or set of row values specified by value expressions. It is most commonly used to generate a “constant table” within a larger command, but it can be us…Description DescriptionManual ChaptersPG18Description vacuumlo is a simple utility program that will remove any “orphaned” large objects from a PostgreSQL database. An orphaned large object (LO) is considered to be any LO whose OID …Description Description of FunctionsManual ChaptersPG18F.50.2. Description of Functions Table F.37 shows the functions provided by this module. These functions provide straightforward XML parsing and XPath queries. Table F.37. xml2 Functions Fun…Description of Functions Designing JSON DocumentsManual ChaptersPG188.14.2. Designing JSON Documents Representing data as JSON can be considerably more flexible than the traditional relational data model, which is compelling in environments where requirement…Designing JSON Documents Destroying a DatabaseManual ChaptersPG1822.5. Destroying a Database Databases are destroyed with the command DROP DATABASE: DROP DATABASE name; Only the owner of the database, or a superuser, can drop a database. Dropping a databa…Destroying a Database Detection by configureManual ChaptersPG18J.2.5. Detection by configure Before you can build the documentation you need to run the configure script, as you would when building the PostgreSQL programs themselves. Check the output nea…Detection by configure Determining Disk UsageManual ChaptersPG1827.6.1. Determining Disk Usage Each table has a primary heap disk file where most of the data is stored. If the table has any columns with potentially-wide values, there also might be a TOAS…Determining Disk Usage Developer OptionsManual ChaptersPG1817.3.3.6. Developer Options Most of the options in this section are only of interest for developing or debugging PostgreSQL. They are not recommended for production builds, except for --enab…Developer Options Developer OptionsManual ChaptersPG1817.4.3.7. Developer Options Most of the options in this section are only of interest for developing or debugging PostgreSQL. They are not recommended for production builds, except for --debu…Developer Options Developer OptionsManual ChaptersPG1819.17. Developer Options The following parameters are intended for developer testing, and should never be used on a production database. However, some of them can be used to assist with the …Developer Options Developer TargetsManual ChaptersPG1817.4.4.2. Developer Targets reformat-dat-files # Rewrite catalog data files into standard format expand-dat-files # Expand all data files to include defaults update-unicode # Update unicode …Developer Targets Deviations from the SQL StandardManual ChaptersPG189.16.2.1. Deviations from the SQL Standard PostgreSQL's implementation of the SQL/JSON path language has the following deviations from the SQL/JSON standard.Deviations from the SQL Standard DiagnosticsManual ChaptersPG18Diagnostics In case of difficulty, see CLUSTER and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any default …Diagnostics DiagnosticsManual ChaptersPG18Diagnostics In case of difficulty, see CREATE DATABASE and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any …Diagnostics DiagnosticsManual ChaptersPG18Diagnostics In case of difficulty, see CREATE ROLE and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any defa…Diagnostics DiagnosticsManual ChaptersPG18Diagnostics In case of difficulty, see DROP DATABASE and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any de…Diagnostics DiagnosticsManual ChaptersPG18Diagnostics In case of difficulty, see DROP ROLE and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any defaul…Diagnostics DiagnosticsManual ChaptersPG18Diagnostics pg_dump internally executes SELECT statements. If you have problems running pg_dump, make sure you are able to select information from the database using, for example, psql. Also…Diagnostics DiagnosticsManual ChaptersPG18Diagnostics When a direct database connection is specified using the -d option, pg_restore internally executes SQL statements. If you have problems running pg_restore, make sure you are able…Diagnostics DiagnosticsManual ChaptersPG18Diagnostics A failure message mentioning semget or shmget probably indicates you need to configure your kernel to provide adequate shared memory and semaphores. For more discussion see Secti…Diagnostics DiagnosticsManual ChaptersPG18Diagnostics In case of difficulty, see REINDEX and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any default …Diagnostics DiagnosticsManual ChaptersPG18Diagnostics In case of difficulty, see VACUUM and psql for discussions of potential problems and error messages. The database server must be running at the targeted host. Also, any default c…Diagnostics dict_int — example full-text search dictionary for integersManual ChaptersPG18F.12. dict_int — example full-text search dictionary for integers dict_int is an example of an add-on dictionary template for full-text search. The motivation for this example dictionary is …dict_int — example full-text search dictionary for integers dict_xsyn — example synonym full-text search dictionaryManual ChaptersPG18F.13. dict_xsyn — example synonym full-text search dictionary dict_xsyn (Extended Synonym Dictionary) is an example of an add-on dictionary template for full-text search. This dictionary typ…dict_xsyn — example synonym full-text search dictionary DictionariesManual ChaptersPG1812.6. Dictionaries Dictionaries are used to eliminate words that should not be considered in a search (stop words), and to normalize words so that different derived forms of the same word wi…Dictionaries Dictionary TestingManual ChaptersPG1812.8.3. Dictionary Testing The ts_lexize function facilitates dictionary testing. ts_lexize(dict regdictionary, token text) returns text[] ts_lexize returns an array of lexemes if the input …Dictionary Testing Differences from SQL Standard and XQueryManual ChaptersPG189.7.3.8. Differences from SQL Standard and XQuery Since SQL:2008, the SQL standard includes regular expression operators and functions that performs pattern matching according to the XQuery …Differences from SQL Standard and XQuery digest()Manual ChaptersPG18F.26.1.1. digest() digest(data text, type text) returns bytea digest(data bytea, type text) returns bytea Computes a binary hash of the given data. type is the algorithm to use. Standard alg…digest() Disable AutocommitManual ChaptersPG1814.4.1. Disable Autocommit When using multiple INSERTs, turn off autocommit and just do one commit at the end. (In plain SQL, this means issuing BEGIN at the start and COMMIT at the end. Som…Disable Autocommit Disable WAL Archival and Streaming ReplicationManual ChaptersPG1814.4.7. Disable WAL Archival and Streaming Replication When loading large amounts of data into an installation that uses WAL archiving or streaming replication, it might be faster to take a …Disable WAL Archival and Streaming Replication disable-mdcManual ChaptersPG18F.26.3.8.5. disable-mdc Do not protect data with SHA-1. The only good reason to use this option is to achieve compatibility with ancient PGP products, predating the addition of SHA-1 protect…disable-mdc DISCARDManual ChaptersPG18DISCARD DISCARD — discard session state Synopsis DISCARD { ALL | PLANS | SEQUENCES | TEMPORARY | TEMP }DISCARD DISCONNECTManual ChaptersPG18DISCONNECT DISCONNECT — terminate a database connection Synopsis DISCONNECT connection_name DISCONNECT [ CURRENT ] DISCONNECT ALLDISCONNECT