hubert depesz lubaczewski <dep...@depesz.com> writes:
> I solved the problem by adding "enable_bitmapscan = false" (and keeping
> the query in original format, with subselect) which caused the plan to
> be ok.
I doubt that solution is any more robust than what you had before ---
in particular, it's likely to fall back to seqscans.
> but I'm much more interested to understand why pg chooses *not* to use
> index which is tailored specifically for the query - it has exactly
> matching where clause, and it indexes the column that we use for
> comparison.
Because the planner thinks it will have to pull a huge number of rows
from the index. Whether the index is "tailored" for the query
is irrelevant if it looks more expensive to use than a seqscan.
regards, tom lane
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