PostgreSQL配置文件--AUTOVACUUM参数

8 AUTOVACUUM参数 AUTOVACUUM PARAMETERS

8.1 autovacuum

字符型默认： autovacuum = on                        Enable autovacuum subprocess?  'on' ，requires track_counts to also be on.表示是否开起autovacuum。特别的，当需要冻结xid（事务ID）时，尽管此值为off，PG也会进行vacuum。 

8.2 log_autovacuum_min_duration

数字型默认： log_autovacuum_min_duration = -1       单位ms在规定时长内未完成的vacuum予以记录日志-1表示禁用，0表示所有的，大于0仅记录超过时间的

8.3 autovacuum_max_workers

数字型默认： autovacuum_max_workers = 3autovacuum最大线程数CPU核多，并且IO好的情况下，可多点，但是注意16*autovacuum mem，会消耗较多内存，所以内存也要有基础。重启数据库生效

8.4 autovacuum_naptime

数字型默认： autovacuum_naptime = 1mintime between autovacuum runs两次vacuum间隔时间

8.5 autovacuum_vacuum_threshold

数字型默认： autovacuum_vacuum_threshold = 50min number of row updates before vacuum达到某表DML操作的最小行数则vacuum

8.6 autovacuum_analyze_threshold

数字型默认： autovacuum_analyze_threshold = 50min number of row updates before analyze激活自动analyze操作的最小行数，analyze有利于对SQL语句进行更精准的plan(这是由于explain用到的pg_class列reltuples and relpages are not updated on-the-fly)

8.7 autovacuum_vacuum_scale_factor

数字型默认： autovacuum_vacuum_scale_factor = 0.2fraction of table size before vacuum表示autovacuum的vacuum操作所需的变更量阈值,当这个表的update/delete的tuple总数大于(pg_class.reltuples*autovacuum_vacuum_scale_factor+autovacuum_vacuum_threshold)时, 触发vacuum操作建议不要太高频率，否则会因为vacuum产生较多的XLOG

8.8 autovacuum_analyze_scale_factor

数字型默认： autovacuum_analyze_scale_factor = 0.1fraction of table size before analyze表示autovacuum的analyze操作所需的变更量阈值,当这个表的INSERT/update/delete的tuple总数大于(pg_class.reltuples*autovacuum_analyze_scale_factor+autovacuum_analyze_threshold)时, 触发analyze操作

8.9 autovacuum_freeze_max_age

数字型默认： autovacuum_freeze_max_age = 200000000maximum XID age before forced vacuum某表的pg_class.relfrozenxid的最大值，如果超出此值则重置xid

8.10 autovacuum_multixact_freeze_max_age

数字型默认： autovacuum_multixact_freeze_max_age = 400000000       maximum multixact age before forced vacuum

8.11 autovacuum_vacuum_cost_delay

数字型默认： autovacuum_vacuum_cost_delay = 20ms    default vacuum cost delay for autovacuum, in milliseconds-1意味着使用vacuum_cost_delay运行一次vacuum的时长，如果超过此值则休眠然后起来接着vacuum(vacuum很好I/O)

8.12 autovacuum_vacuum_cost_limit

数字型默认： autovacuum_vacuum_cost_limit = -1  default vacuum cost limit for autovacuum-1意味着使用vacuum_cost_delay

8.13 autovacuum_vacuum_cost_delay

数字型默认： autovacuum_vacuum_cost_delay = 20ms   default vacuum cost delay for autovacuum, in milliseconds; -1 means use vacuum_cost_delay当autovacuum进程即将执行时，对vacuum执行cost进行评估，如果超过autovacuum_vacuum_cost_limit的值时，则延迟，这个延迟的时间值即为改成的值.

8.14 autovacuum_vacuum_cost_limit

数字型默认： autovacuum_vacuum_cost_limit = -1     default vacuum cost limit for autovacuum, -1 means use vacuum_cost_limitautovacuum进程的评估阀值，-1表示使用vacuum_cost_limit值，如果在执行 autovacuum进程期间评估的cost超过autovacuum_vacuum_cost_limit,则autovacuum进程则会休眠