The VACUUM command in PostgreSQL is used to reclaim storage occupied by dead tuples and update table statistics. Dead tuples are created due to updates and deletions but are not immediately removed to maintain
Plain VACUUM: Frees up space for re-use 1 VACUUM [tablename] Full VACUUM: Locks the database table, and reclaims more space than a plain VACUUM 1 2 3 4 /* Before Postgres 9.0: */ VACUUM FULL /* Postgres 9.0+: */ VACUUM(FULL) [tablename] Full VACUUM and ANALYZE: Per...
Note that VACUUM does not shrink a table when it runs, unless there is a large run of space at the end of a table, and nobody is accessing the table when we try to shrink it. To properly shrink a table, you need VACUUM FULL. That locks up the whole table for a long time, and...
postgresql vacuum table 2down vote according toDocumentation VACUUM reclaims storage occupied by dead tuples. But according tothis post Dead rows are deleted rows that will later be reused for new rows from INSERTs or UPDATEs. Some dead rows (or reserved free space) can be particularly useful ...
一、 table_relation_vacuum函数 1. 函数定义 table_relation_vacuum函数(tableam.h文件),本篇继续学习。 如前面所说,手动和autovacuum触发的vacuum操作均会走到该函数,需要对表加4级锁。该函数针对lazy vacuum,因此vacuum full,CLUSTER,ANALYZE操作不会走到它。
-- our new table, same structure as the example in -- the previous section CREATE TABLE github_columnar_events ( LIKE github_events ) PARTITION BY RANGE (created_at); -- create partitions to hold two hours of data each SELECT create_time_partitions( table_name := 'github_columnar_events...
“freeze” a table, and the database can get dangerously close to the point that the wraparound data corruption can occur. Since vacuuming the indexes takes most of the time, sometimes, you want to tell PostgreSQL to skip that step, and just vacuum the heap so that the wraparound danger...
For PostgreSQL versions older than v13, you can achieve a similar effect by triggering anti-wraparound vacuum earlier, so that it becomes less disruptive. For example, if you want to vacuum a table every 100000 transactions, you can set this storage parameter: ...
Thus, a single query could use multiple work_mem in total, for example, in a nested string of hash joins. maintenance_work_mem This determines the maximum amount of memory used for maintenance operations like VACUUM, CREATE INDEX, ALTER TABLE ADD FOREIGN KEY, and data-loading operations. ...
; (No rows) 实际上,这个查询还不是完美,因为锁等待实际上是一个TRUNCATE TABLE的操作造成的,而因为AUTO VACUUM FREEZE和TRUNCATE操作冲突了,所以这两个会话的锁都会对后面的DML造成影响,实际上,我们要找到的应该是级别最高的锁(TRUNCATE),干掉这个才是最重要的,普通的vacuum并不会和DML冲突。所以我们需要改进一...