<zhabala@telecom.cz> writes:
> first of all thank You for Your response. But here is the
> reality. Table formula have about 450000 rows at this time.
> The id_formula column is int4 defined as not null primary key.
It is eh? Have you done a VACUUM ANALYZE on this table lately?
4500 rows (1%) would be the default match estimate in the absence of
any statistics.
> And the index have clause unique, but backend still don't use it.
7.2 will know enough to realize that presence of a unique index means
the column is unique, but existing releases only look at the VACUUM
ANALYZE statistics. No statistics = bad plan.
regards, tom lane
