PostgreSQL ????????
???????????? ???????[ 2014/3/6 9:18:37 ] ????????????? ??? ??? PostgreSQL
????????????????
??????PostgreSQL?У????delete??update??????????μ??????в???б?????????????????汾?????е?????????????е?????????????????????????????е?????仯????????????????????????????????佫???ú????????????????仯??????????????????????????仯?????????????VACUUM??????
????VACUUM????????????????VACUUM??VACUUM FULL??????????????????±??
???????????1滮??????
????PostgreSQL????滮?????????·???????????????????????????????????????????滮????Щ????????ANALYZE???????????????????????????????????VACUUM??????????????????????????VACUUM ANAYLYZE table_name???????????????VACUUM?????ANALYZE?????????(VACUUM)??????????????????????????????ANALYZE???????????????????????????μ??????????????????????????????????????????????2?????????????????????иò?????
????????????????????????????????????????ANALYZE???????????????????????????????±????????????????ANALYZE?????????????????????????????????????????????ANALYZE?????????Ч??????????????????????ANALYZE????????????????????????????????????????????????????????????????????????????в?????????????????????????????????з???????????????????????????????и????
?????????????????????????????????????????????ε????????磺
????ALTER TABLE testtable ALTER COLUMN test_col SET STATISTICS 200
????????????????Χ??0--1000???????????????????????????????????????????ANALYZE??????е??????????????????????-1?????????ε??????????????????????????????????????????????????????????????????
postgres=# show default_statistics_target;
default_statistics_target
---------------------------
100
(1 row)
??????????????????????????????????????100(10%)??
??????
???·???
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