Andreas Brandl <m...@3.141592654.de> writes:
> we're currently investigating a statistics issue on postgres. We have some 
> tables which frequently show up with strange values for n_live_tup. If you 
> compare those values with a count on that particular table, there is a 
> mismatch of factor 10-30. This causes the planner to come up with very bad 
> plans (we also have this issue on bigger table like the one below).

The planner doesn't use n_live_tup; the only thing that that's used for
is decisions about when to autovacuum/autoanalyze.  So you have two
problems here not one.

Can you provide a test case for the n_live_tup drift?  That is,
something that when done over and over causes n_live_tup to get further
and further from reality?

                        regards, tom lane

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