vacuumdb 清理空間問(wèn)題

dead_Joker

對(duì)于經(jīng)常增刪數(shù)據(jù)的表，做vacuumdb操作（不加f參數(shù)），能夠重用空間。

但這樣做，就像物理硬盤(pán)一樣，會(huì)不會(huì)也產(chǎn)生碎片呢？

dead_Joker

{:3_198:}沒(méi)人回呀

asdf2110

應(yīng)該不會(huì)，vacuum 會(huì)把已刪除的掛在空閑鏈表上，下次分配時(shí)直接在空閑鏈表上找可用空間，具體細(xì)節(jié)不太清楚

wang1352083

vacuum 將空間返回給os

dead_Joker

thanks dudes

longshort

這個(gè)基本上不是問(wèn)題，每天定時(shí)運(yùn)行一次會(huì)很輕松，碎片不會(huì)累積。

yanghong709

vacuum的時(shí)候，只是把不需要的數(shù)據(jù)打上標(biāo)志，表示這些數(shù)據(jù)已經(jīng)過(guò)期，可以覆蓋這些數(shù)據(jù)了。而vacuum full就是徹底的回收數(shù)據(jù)所占用的空間，返還給OS。

jiang870320

vacuum analyse verbose 會(huì)，select relname,relkind,reltuples,relpages from pg_class where relkind='i' and relname like 'xxx'; 對(duì)比前后差距

歸隱鄉(xiāng)村

Plain VACUUM (without FULL) simply reclaims space and makes it available for re-use. extra space is not returned to the operating system (in most cases); it’s just kept available for re-use within the same table. VACUUM FULL rewrites the entire contents of the table into a new disk file with no extra space, allowing unused space to be returned to the operating system. This form is much slower and requires an exclusive lock on each table while it is being processed.