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Column Check ConstraintsManual ChaptersPG18Column Check Constraints The SQL standard says that CHECK column constraints can only refer to the column they apply to; only CHECK table constraints can refer to multiple columns. PostgreSQ…Column Check Constraints Column LabelsManual ChaptersPG187.3.2. Column Labels The entries in the select list can be assigned names for subsequent processing, such as for use in an ORDER BY clause or for display by the client application. For examp…Column Labels Column ListsManual ChaptersPG1829.5. Column Lists Each publication can optionally specify which columns of each table are replicated to subscribers. The table on the subscriber side must have at least all the columns that…Column Lists Column ReferencesManual ChaptersPG184.2.1. Column References A column can be referenced in the form: correlation.columnname correlation is the name of a table (possibly qualified with a schema name), or an alias for a table de…Column References column_column_usageManual ChaptersPG1835.12. column_column_usage The view column_column_usage identifies all generated columns that depend on another base column in the same table. Only tables owned by a currently enabled role a…column_column_usage column_domain_usageManual ChaptersPG1835.13. column_domain_usage The view column_domain_usage identifies all columns (of a table or a view) that make use of some domain defined in the current database and owned by a currently en…column_domain_usage column_encryptExtensionsExtensionsTransparent column-level encryption with encrypted_text and encrypted_bytea types column_encrypt SecuritySecurity · Extensions column_optionsManual ChaptersPG1835.14. column_options The view column_options contains all the options defined for foreign table columns in the current database. Only those foreign table columns are shown that the current …column_options column_privilegesManual ChaptersPG1835.15. column_privileges The view column_privileges identifies all privileges granted on columns to a currently enabled role or by a currently enabled role. There is one row for each combina…column_privileges column_udt_usageManual ChaptersPG1835.16. column_udt_usage The view column_udt_usage identifies all columns that use data types owned by a currently enabled role. Note that in PostgreSQL, built-in data types behave like user-…column_udt_usage columnarExtensionsExtensionsHydra Columnar extension hydra AnalyticsAnalytics · Extensions columnsManual ChaptersPG1835.17. columns The view columns contains information about all table columns (or view columns) in the database. System columns (ctid, etc.) are not included. Only those columns are shown tha…columns Combining Multiple IndexesManual ChaptersPG1811.5. Combining Multiple Indexes A single index scan can only use query clauses that use the index's columns with operators of its operator class and are joined with AND. For example, given …Combining Multiple Indexes Combining Multiple Row FiltersManual ChaptersPG1829.4.6. Combining Multiple Row Filters If the subscription has several publications in which the same table has been published with different row filters (for the same publish operation), th…Combining Multiple Row Filters Combining Queries (UNION, INTERSECT, EXCEPT)Manual ChaptersPG187.4. Combining Queries (UNION, INTERSECT, EXCEPT) The results of two queries can be combined using the set operations union, intersection, and difference. The syntax is query1 UNION [ALL] qu…Combining Queries (UNION, INTERSECT, EXCEPT) Command Execution FunctionsManual ChaptersPG1832.3. Command Execution Functions Once a connection to a database server has been successfully established, the functions described here are used to perform SQL queries and commands.Command Execution Functions Command-Line EditingManual ChaptersPG18Command-Line Editing psql uses the Readline or libedit library, if available, for convenient line editing and retrieval. The command history is automatically saved when psql exits and is rel…Command-Line Editing COMMENTManual ChaptersPG18COMMENT COMMENT — define or change the comment of an object Synopsis COMMENT ON { ACCESS METHOD object_name | AGGREGATE aggregate_name ( aggregate_signature ) | CAST (source_type AS target_t…COMMENT COMMENTSQL CommandsReferenceCOMMENT Other Objects 10 define or change the comment of an object COMMENT ON { ACCESS METHOD object_name | AGGREGATE aggregate_name ( aggregate_signature ) | CAST (source_type AS target_typ…SQL Commands · Other Objects Comment Information FunctionsManual ChaptersPG189.27.6. Comment Information Functions The functions shown in Table 9.82 extract comments previously stored with the COMMENT command. A null value is returned if no comment could be found for…Comment Information Functions CommentsManual ChaptersPG184.1.5. Comments A comment is a sequence of characters beginning with double dashes and extending to the end of the line, e.g.: -- This is a standard SQL comment Alternatively, C-style block …Comments COMMITManual ChaptersPG18COMMIT COMMIT — commit the current transaction Synopsis COMMIT [ WORK | TRANSACTION ] [ AND [ NO ] CHAIN ]COMMIT COMMITSQL CommandsReferenceCOMMIT Transactions 10 commit the current transaction COMMIT [ WORK | TRANSACTION ] COMMIT commits the current transaction. All changes made by the transaction become visible to others and a…SQL Commands · Transactions COMMIT PREPAREDManual ChaptersPG18COMMIT PREPARED COMMIT PREPARED — commit a transaction that was earlier prepared for two-phase commit Synopsis COMMIT PREPARED transaction_idCOMMIT PREPARED COMMIT PREPAREDSQL CommandsReferenceCOMMIT PREPARED Transactions 10 commit a transaction that was earlier prepared for two-phase commit COMMIT PREPARED transaction_id COMMIT PREPARED commits a transaction that is in prepared s…SQL Commands · Transactions commit_delayConfigurationReferencecommit_delay Write-Ahead Log 10 commit_delay adds a time delay, measured in microseconds, before a WAL flush is initiated. This can improve group commit throughput by allowing a larger numbe…Configuration · Write-Ahead Log commit_siblingsConfigurationReferencecommit_siblings Write-Ahead Log 10 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…Configuration · Write-Ahead Log commit_timestamp_buffersConfigurationReferencecommit_timestamp_buffers Resource Usage 17 Specifies the amount of memory to use to cache the contents of pg_commit_ts (see Table 65.1). If this value is specified without units, it is taken…Configuration · Resource Usage CommitDelayWait EventsReferenceCommitDelay Timeout 19 Waiting for commit delay before WAL flush. 20Wait Events · Timeout Committed Transaction Information FunctionsManual ChaptersPG189.27.9. Committed Transaction Information Functions The functions shown in Table 9.87 provide information about when past transactions were committed. They only provide useful data when the …Committed Transaction Information Functions CommitTsWait EventsReferenceCommitTs LWLock 10 Waiting to read or update the last value set for the transaction timestamp. 11 12 13 Waiting to read or update the last value set for a transaction commit timestamp. 14 15…Wait Events · LWLock CommitTsBufferWait EventsReferenceCommitTsBuffer LWLock 10 Waiting for I/O on commit timestamp buffer. 11 12 13 Waiting for I/O on a commit timestamp SLRU buffer. 14 15 16 17 18 19 20 9.6 A brief sample is normal around shor…Wait Events · LWLock CommitTsSLRUWait EventsReferenceCommitTsSLRU LWLock 10 Waiting to read or update transaction commit timestamps. 11 12 13 Waiting to access the commit timestamp SLRU cache. 14 15 16 17 18 19 20 9.6 A brief sample is normal …Wait Events · LWLock Common OptionsManual ChaptersPG18Common Options pgbench also accepts the following common command-line arguments for connection parameters and other common settings: --debug # Print debugging output. -h hostname--host=hostn…Common Options Common Table Expression MaterializationManual ChaptersPG187.8.3. Common Table Expression Materialization A useful property of WITH queries is that they are normally evaluated only once per execution of the parent query, even if they are referred to…Common Table Expression Materialization COMMUTATORManual ChaptersPG1836.15.1. COMMUTATOR The COMMUTATOR clause, if provided, names an operator that is the commutator of the operator being defined. We say that operator A is the commutator of operator B if (x A…COMMUTATOR compact_uuidExtensionsExtensionsUUID type with canonical 22-character Base64url text uuid base64url compact_uuid Data typesData types · Extensions Comparison Functions and OperatorsManual ChaptersPG189.2. Comparison Functions and Operators The usual comparison operators are available, as shown in Table 9.1. Table 9.1. Comparison Operators Operator Description datatype < datatype → boolea…Comparison Functions and Operators Comparison of Different SolutionsManual ChaptersPG1826.1. Comparison of Different Solutions Shared Disk Failover Shared disk failover avoids synchronization overhead by having only one copy of the database. It uses a single disk array that is…Comparison of Different Solutions CompatibilityManual ChaptersPG18Compatibility ALLOCATE DESCRIPTOR is specified in the SQL standard.Compatibility