Il giorno sab, 15/07/2006 alle 13.04 -0700, Joe Conway ha scritto:
Gabriele Turchi wrote:
Running an ANALYZE really change the plan, now it is fast as before

On the production system a VACUUM FULL ANALYZE is run every morning
after a clean-up, when the "registrazioni" table is empty. During the
day this table fills up (about 500 record any day), and apparently the
performances are free-falling very quickly. This behaviour has not
changed between the old and the new installation.

Can you suggest an easy way to collect and keep up-to-date these
statistics in a very low-impact way?
Why not just periodically (once an hour?) run "ANALYZE registrazioni;"
during the day. This will only update the statistics, and should be very
low impact.
This is my "solution" too... but: is enough? Or else: there is a better
way to do this? If the performance in the better case is 50 times faster
than the worse case, during an hour (50/100 record inserted in
"registrazioni") how much the performance can fall before the new
"ANALYZE" is run? Otherwise, running ANALYZE more frequently can badly
affect the overall performance?

A so big difference in postgres performance, can be considered a bug or
a over-optimization in the plan making? Why (at least apparently) the
8.0 version is not affected?


---------------------------(end of broadcast)---------------------------
TIP 6: explain analyze is your friend
Thank you all very much,

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postedJul 15, '06 at 2:14p
activeJul 18, '06 at 11:29a



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