Using ANALYZE to optimize PostgreSQL queries Vacuuming isn't the only periodic maintenance your database needs. databases that are completely read-only and will not receive This is a handy combination form for routine maintenance scripts. to report a documentation issue.

When VERBOSE is specified, VACUUM emits progress messages to indicate which table is currently being processed. table more than a plain VACUUM Specifies a non-negative integer value passed to the selected option. This feature is known as parallel vacuum. VACUUM ANALYZE performs a VACUUM and then an ANALYZE for each selected table. When VERBOSE is specified, VACUUM emits progress messages to indicate which In normal PostgreSQL operation, tuples that are We recommend that active production databases be vacuumed frequently (at least nightly), in order to remove dead rows. See ANALYZE for more details about its processing. After adding or deleting a large number of rows, it might be a good idea to issue a VACUUM ANALYZE command for the affected table.

try to compact the table to the minimum number of disk blocks. The daemon will run VACUUM and ANALYZE at regular intervals. Defaults to all columns. See Section 66.4.1 for details.

However, database owners are allowed to vacuum all tables in their databases, except shared catalogs. To disable this feature, one can use PARALLEL option and specify parallel workers as zero. Also, while VACUUM ordinarily processes all partitions of specified partitioned tables, this option will cause VACUUM to skip all partitions if there is a conflicting lock on the partitioned table. (The restriction for shared catalogs means that a true database-wide VACUUM can only be performed by a superuser.) An example is when you have deleted or updated most of the rows in a table and would like the table to physically shrink to occupy less disk space and allow faster table scans. The name of a specific column to analyze. We recommend that active production databases be vacuumed frequently (at least nightly), in order to remove dead rows. ANALYZE. This option has no effect for tables that do not have an index and is ignored if the FULL option is used. Therefore it's necessary to do VACUUM periodically, especially on frequently-updated tables. VACUUM — garbage-collect and optionally analyze a database. In the default PostgreSQL configuration, the AUTOVACUUM daemon is enabled and all required configuration parameters are set as needed. It also allows us to leverage multiple CPUs in order to process indexes. may reclaim more space, but takes much longer and With a parameter, VACUUM processes only that table. See Chapter 21 for details. Defaults to PostgreSQL vacuuming (autovacuum or manual vacuum) minimizes table bloats and prevents transaction ID wraparound. Various statistics about the tables are printed as well. Selects "full" vacuum, which can reclaim more space, but takes much longer and exclusively locks the table. Additionally, VACUUM ANALYZE may still block when acquiring sample rows from partitions, table inheritance children, and some types of foreign tables. your experience with the particular feature or requires further clarification, Defaults to all tables in the current Its only intended usage is in connection with VACUUM causes a substantial increase in I/O traffic, which might cause poor performance for other active sessions. when you have deleted most of the rows in a table and would like Prints a detailed vacuum activity report for each If a column list is specified, ANALYZE must also be specified.

If you see anything in the documentation that is not correct, does not match Updates statistics used by the planner to determine the most efficient way to execute a query. open transactions in the same database, then it is guaranteed deleted or obsoleted by an update are not physically removed from

This is a handy combination form for routine maintenance scripts. With a list, VACUUM processes only those table(s). With no parameter, VACUUM processes Various statistics about the Prints a detailed vacuum activity report for each table. Also, while VACUUM ordinarily processes all partitions of specified partitioned tables, this option will cause VACUUM to skip all partitions if there is a conflicting lock on the partitioned table. Updates statistics used by the planner to determine the Copyright © 1996-2020 The PostgreSQL Global Development Group, PostgreSQL 13.1, 12.5, 11.10, 10.15, 9.6.20, & 9.5.24 Released. In normal PostgreSQL operation, tuples that are deleted or obsoleted by an update are not physically removed from their table; they remain present until a VACUUM is done. normal reading and writing of the table, as an exclusive lock is Additionally, VACUUM ANALYZE may still block when acquiring sample rows from partitions, table inheritance children, and some types of foreign tables. So parallel workers are launched only when there are at least 2 indexes in the table. table to vacuum. VACUUM FULL will usually shrink the This will update the system catalogs with the results of all recent changes, and allow the PostgreSQL query planner to make better choices in planning queries. When the option list is surrounded by parentheses, the options can be written in any order. Please note that it is not guaranteed that the number of parallel workers specified in integer will be used during execution. Selects aggressive “freezing” of tuples. With no parameter, VACUUM processes every table in the current database that the current user has permission to vacuum. The FULL option is not recommended for Examples: ANALYZE users; collects statistics for users table. your experience with the particular feature or requires further clarification,

To vacuum a table, one must ordinarily be the table's owner or a superuser. Without parentheses, options must be specified in exactly the order shown above. Copyright © 1996-2020 The PostgreSQL Global Development Group. Plain VACUUM (without FULL) simply reclaims space and makes it available for re-use. VACUUM periodically, especially on Plain VACUUM (without FULL) simply reclaims space and makes it available for re-use. deleted tuples. most efficient way to execute a query. routine maintenance VACUUM operations. This form of the command can operate in parallel … Setting this option to false may be useful to avoid ACCESS EXCLUSIVE lock on the table that the truncation requires. This option disables all page-skipping behavior, and is intended to be used only when the contents of the visibility map are suspect, which should happen only if there is a hardware or software issue causing database corruption. For parallel vacuum, each worker sleeps in proportion to the work done by that worker. This is normally the desired behavior and is the default unless the vacuum_index_cleanup option has been set to false for the table to be vacuumed. The name (optionally schema-qualified) of a specific table to vacuum. To clean a single table onek, analyze it for the optimizer and print a detailed vacuum activity report: There is no VACUUM statement in the SQL standard. VACUUM FULL will usually shrink the table more than a plain VACUUM would. FREEZE is a special-purpose option Specifies that VACUUM should not wait for any conflicting locks to be released when beginning work on a relation: if a relation cannot be locked immediately without waiting, the relation is skipped. For tables with GIN indexes, VACUUM (in any form) also completes any pending index insertions, by moving pending index entries to the appropriate places in the main GIN index structure. ANALYZE VERBOSE users; does exactly the same plus prints progress messages. However, extra space is not returned to the operating system (in most cases); it's just kept available for re-use within the same table. extensive processing, including moving of tuples across blocks to In this article, we will share a few best practices for VACUUM and ANALYZE.

After adding or deleting a large number of rows, it might be a good idea to issue a VACUUM ANALYZE command for the affected table. table.

You also need to analyze the database so that the query planner has table statistics it can use when deciding how to execute a query. VACUUM reclaims storage occupied by dead tuples. frequently-updated tables. Aggressive freezing is always performed when the table is rewritten, so this option is redundant when FULL is specified. SQL standard. Selects aggressive "freezing" of tuples.

See ANALYZE for more details about its processing. their table; they remain present until a VACUUM is done. (The restriction for shared catalogs means that a true database-wide VACUUM can only be performed by a superuser.) The PARALLEL option is used only for vacuum purposes. With a parameter, VACUUM processes only that table. Therefore, it is sometimes advisable to use the cost-based vacuum delay feature. PostgreSQL ANALYZE command collects statistics about specific table columns, entire table, or entire database. VACUUM causes a substantial increase in I/O traffic, which might cause poor performance for other active sessions. For more information about automatic and manual vacuuming, see Section 23.1. However, database owners are allowed to vacuum all tables in their databases, except shared catalogs. This is a handy Specifying FREEZE is equivalent to performing VACUUM with the vacuum_freeze_min_age and vacuum_freeze_table_age parameters set to zero. For more information about automatic and manual vacuuming, see Section 24.1. An example is when you have deleted or updated most of the rows in a table and would like the table to physically shrink to occupy less disk space and allow faster table scans. When the option list is surrounded by parentheses, the options can be written in any order. Simply put: Make sure you're running ANALYZE frequently enough, preferably via autovacuum.

VACUUM ANALYZE performs a VACUUM and then an ANALYZE for each selected table. VACUUM ANALYZE performs a VACUUM and then an ANALYZE for each selected table. VACUUM ANALYZE performs a VACUUM and then an ANALYZE for each selected table. To vacuum a table, one must ordinarily be the table's owner or a superuser. This form is much slower and requires an exclusive lock on each table while it is being processed.

VACUUM cannot be executed inside a transaction block. table is currently being processed. See Section 19.4.4 for details. PostgreSQL includes an "autovacuum" facility which can automate routine vacuum maintenance. VACUUM FULL does more

For tables with GIN indexes, VACUUM (in any form) also completes any pending index insertions, by moving pending index entries to the appropriate places in the main GIN index structure. When VERBOSE is specified, VACUUM emits progress messages to indicate which table is currently being processed. Copyright © 1996-2020 The PostgreSQL Global Development Group, PostgreSQL 13.1, 12.5, 11.10, 10.15, 9.6.20, & 9.5.24 Released. This form is much slower and requires an exclusive lock on each table while it is being processed. Therefore, it is sometimes advisable to use the cost-based vacuum delay feature. Specifying FREEZE is equivalent to performing VACUUM with the vacuum_freeze_min_age and vacuum_freeze_table_age parameters set to zero. If you have the damon enabled, these commands can … The parenthesized syntax was added in PostgreSQL 9.0; the unparenthesized syntax is deprecated. Also, while VACUUM ordinarily processes all partitions of specified partitioned tables, this option will cause VACUUM to skip all partitions if there is a conflicting lock on the partitioned table. Perform index vacuum and index cleanup phases of VACUUM in parallel using integer background workers (for the details of each vacuum phase, please refer to Table 27.37). Defaults to all columns. We recommend that active production databases be vacuumed

Note that even with this option, VACUUM may still block when opening the relation's indexes. idea to issue a VACUUM ANALYZE command

Plain VACUUM (without FULL) simply reclaims space and makes it available for re-use.