VACUUM performs an aggressive scan if the table's pg_class.relfrozenxid field has reached the age specified by this setting. An aggressive scan differs from a regular VACUUM in that it visits every page that might contain unfrozen XIDs or MXIDs, not just those that might contain dead tuples. The default is 150 million transactions. Although users can set this value anywhere from zero to two billions, VACUUM will silently limit the effective value to 95% of autovacuum_freeze_max_age, so that a periodical manual VACUUM has a chance to run before an anti-wraparound autovacuum is launched for the table. For more information see vacuum-for-wraparound.
- pgsql: Fix freezing of a dead HOT-updated tuple
- Temporary tables prevent autovacuum, leading to XID wraparound
- pgsql: Fix traversal of half-frozen update chains
- Re: found xmin from before relfrozenxid on pg_catalog.pg_authid
- Re: Changing the autovacuum launcher scheduling; oldest table first algorithm