为了移除死元组(dead tuples),vacuum 进程提供了两种模式:Concurrent VACUUM和Full VACUUM。Concurrent VACUUM通常简称为VACUUM,移除表文件每一页的死元组,VACUUM在运行的同时其它事务能够读取表。相比之下,Full VACUUM 删除死元组并堆整个文件中的活动元组进行碎片整理,Full VACUUM运行期间,其
1 2 3 4 /* Before Postgres 9.0: */ VACUUM FULL VERBOSE ANALYZE [tablename] /* Postgres 9.0+: */ VACUUM(FULL, ANALYZE, VERBOSE) [tablename] ANALYZE ANALYZE gathers statistics for the query planner to create the most efficient query execution paths. Per PostgreSQL documentation, ...
the administrator can do VACUUM FULL of the table. In this case, the table and all its indexes are rebuilt from scratch and the data are packed in a mostly compact way (of course, thefillfactorparameter taken into account). During the rebuild, PostgreSQL first rebuilds the table and then ...
an Autovacuum worker can only process a single table at a time. If we were to rely on a single worker, it could take hours or even days to vacuum such a database. So Postgres allows us to specifyautovacuum_max_workersto increase the amount of parallel workers performing this crucial task...
WAL usage: 1 records, 0 full page images, 245 bytes system usage: CPU: user: 0.00 s, system: 0.00 s, elapsed: 0.01 s As described in detail inresearch notesby one of our team members, there are several processes in Postgres that can cause the "xmin" value that's effective for a ...
"postgres.public.pgbench_accounts" system usage: CPU 0.06s/0.18u sec elapsed 3.66 sec Most of the preceding global parameters can also be set at the table level. For example, if you think that you don't want a table to be autovacuumed, then you can set: ...
while true; do psql -c "vacuum full pg_class" regression; usleep 100000; done Even after fixing the cache-reset-recovery-order problem I described yesterday, there are still occasional bizarre failures, for example in this bit of truncate.sql: ...
The new Postgres 14 code is further optimized by having a pre-check to see if the tuples are already in the correct reverse item pointer offset order. If the tuples are in the correct order, then there is no need to use the temporary buffer. We then move only tuples that come earlie...
ERROR: CONCURRENTLY can only be specified with VACUUM FULL [local] postgres@demo:5432-36097=# vacuum full (concurrently) full aircrafts_data; ERROR: syntax error at or near "(" LINE 1: vacuum full (concurrently) full aircrafts_data;