On 20 Červen 2014, 5:33, Pavel Stehule wrote: > 2014-06-20 1:44 GMT+02:00 Huang, Suya <Suya.Huang@xxxxxxxxxxxxxxx>: >> >> Thanks Pavel, to be more clear, what does " pg_stat_reset "really reset? >> In the document it says " Reset all statistics counters for the current >> database to zero(requires superuser privileges) ". I thought it would >> reset all statistics of all tables/indexes, thus why I am thinking of >> re-run analyze database to gather statistics. Because if table/indexes >> don't have statistics, the query plan would be affected which is not a >> good >> thing to a production box... I'm not so sure if I understand "run >> statistics" you mentioned here. >> > > you have true - anyway you can clean a content of this directory - but if > your database has lot of database objects, your stat file will have a > original size very early > > Pavel > No, he's not right. Suya, as I wrote in my previous message, there are two kinds of statistics in PostgreSQL a) data distribution statistics - histograms, MCV lists, number of distinct values, ... - stored in regular tables - used for planning - collected by ANALYZE - not influenced by pg_stat_reset() at all b) runtime statistics - number of scans for table/index, rows fetched from table/index, ... - tracks activity within the database - stored in pgstat.stat file (or per-db files in the recent releases) - used for monitoring, not for planning - removed by pg_stat_reset() So running pg_stat_reset will not hurt planning at all. regards Tomas
