Re: Postgres 15 SELECT query doesn't use index under RLS - Mailing list pgsql-performance

Hi Tomek,

Unfortunately, I didn't dig into this. This request is recommended to provide when describing slow query issues, but looks like it relates to JOINs in the query, which we don't have.

Kind regards,

Alexander

Hi Alexander!

Apart from the problem you are writing about I'd like to ask you to explain how you interpret counted frac_MCV - for me it has no sense at all to summarize most_common_freqs.

Please rethink it and explain what was the idea of such SUM ? I understand that it can be some measure for ratio of NULL values but only in some cases when n_distinct is small.

regards

Statistics: n_distinct, MCV, histogram

Useful to check statistics leading to bad join plan. SELECT (SELECT sum(x) FROM unnest(most_common_freqs) x) frac_MCV, tablename, attname, inherited, null_frac, n_distinct, array_length(most_common_vals,1) n_mcv, array_length(histogram_bounds,1) n_hist, correlation FROM pg_stats WHERE attname='...' AND tablename='...' ORDER BY 1 DESC;

Returns 0 rows.

Kind regards,

Alexander