Re: get_actual_variable_range vs idx_scan/idx_tup_fetch

Marko Tiikkaja <marko(at)joh(dot)to> writes:
> This week we had one of the most annoying problems I've ever encountered
> with postgres. We had a big index on multiple columns, say, foo(a, b,
> c). According to pg_stat_all_indexes the index was being used *all the
> time*. However, after looking into our queries more closely, it turns
> out that it was only being used to look up statistics for the foo.a
> column to estimate merge scan viability during planning. But this took
> hours for two people to track down.

> So what I'd like to have is a way to be able to distinguish between
> indexes being used to answer queries, and ones being only used for stats
> lookups during planning.

Why? Used is used.

regards, tom lane