Help Center/ Data Warehouse Service / SQL Syntax Reference/ SQL Syntax Reference (9.1.1.x)/ Functions and Operators/ System Administration Functions/ Cache Management Functions
Updated on 2025-10-10 GMT+08:00
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Cache Management Functions

Cache management functions are available for clusters of version 9.1.1.100 and later. The functions release caches from shared buffers, accelerating query and optimizing database performance.

Only the system administrator can execute this function.

The three types of interfaces are provided for releasing caches.

pg_buffercache_evict(bufferid integer)

Description: Releases the buffer with the specified ID.

Return type: bool

Return value description: Whether the buffer is released and successfully written to a disk.

Example:

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SELECT pg_catalog.pg_buffercache_evict(1);
 pg_buffercache_evict 
----------------------
 t
(1 row)

pg_buffercache_evict(nsp_name name, rel_name name, partition_name name, temp_nsp_name name)

Description: Releases all unpinned buffers of a specified table on the current instance.

Parameter description: Different parameter values need to be specified based on the table type. For details, see Table 2.

Return type: integer

Return value description: Number of buffers that are successfully released.

Example:

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SELECT pg_catalog.pg_buffercache_evict('public', 't1', NULL, NULL);
 pg_buffercache_evict 
----------------------
                    4
(1 row)

pgxc_buffercache_evict(nsp_name name, rel_name name, partition_name name, temp_nsp_name name)

Description: Releases all unpinned buffers of a specified table on all instances.

Parameter description: Different parameter values need to be specified based on the table type. For details, see Table 2.

Return type: integer

Return value description: Number of buffers that are successfully released.

Example:

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SELECT pg_catalog.pgxc_buffercache_evict('public', 't1', NULL, NULL);
 pgxc_buffercache_evict 
------------------------
                     10
(1 row)

pg_buffercache_evict()

Description: Releases all unpinned buffers on the current instance.

Return type: integer

Return value description: Number of buffers that are successfully released.

Example:

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SELECT pg_catalog.pg_buffercache_evict();
 pg_buffercache_evict 
----------------------
                 2654
(1 row)

pgxc_buffercache_evict()

Description: Releases all unpinned buffers on all instance.

Return type: integer

Return value description: Number of buffers that are successfully released.

Example:

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SELECT pg_catalog.pgxc_buffercache_evict();
 pgxc_buffercache_evict 
------------------------
                  10881
(1 row)
Parent Topic: System Administration Functions