First off, this is posted to the wrong list -- this list is for discussion of development of the PostgreSQL product. There is a list for performance questions where this belongs: pgsql-performa...@postgresql.org. I'm moving this to the performance list with a blind copy to the -hackers list so people know where the discussion went. Nick Raj <nickrajj...@gmail.com> wrote: > When i execute the query first time, query takes a quite longer > time but second time execution of the same query takes very less > time (despite execution plan is same) > Why the same plan giving different execution time? (Reason may be > data gets buffered (cached) for the second time execution) Why > there is so much difference? Because an access to a RAM buffer is much, much faster than a disk access. > Which option will be true? It depends entirely on how much of the data needed for the query is cached. Sometimes people will run a set of queries to "warm" the cache before letting users in. > MY postgresql.conf file having setting like this (this is original > setting, i haven't modify anything) > shared_buffers = 28MB > #work_mem = 1MB # min 64kB > #maintenance_work_mem = 16MB # min 1MB If you're concerned about performance, these settings (and several others) should probably be adjusted: http://wiki.postgresql.org/wiki/Tuning_Your_PostgreSQL_Server -Kevin
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