Julius T <julius@nsoft.lt> wrote:
> The question is why the difference of value provided by EXPLAIN
> ANALYZE and observed one is so big?
There can be a number of reasons. The time to transmit the query
results to the client is one that jumps to mind, if the query
generates a large result set. Parts of what you described might
suggest checkpoint issues, depending on the query mix, the
PostgreSQL version, the hardware and the OS. You haven't given us
enough information to even start to guess which of these or other
issues might be involved.
Please read this page, and repost with more information:
http://wiki.postgresql.org/wiki/SlowQueryQuestions
-Kevin