pgsql: Support boolean columns in functional-dependency statistics. - Mailing list pgsql-committers

From Tom Lane
Subject pgsql: Support boolean columns in functional-dependency statistics.
Date
Msg-id E1eLtyA-0006Zs-Ph@gemulon.postgresql.org
Whole thread Raw
List pgsql-committers
Support boolean columns in functional-dependency statistics.

There's no good reason that the multicolumn stats stuff shouldn't work on
booleans.  But it looked only for "Var = pseudoconstant" clauses, and it
will seldom find those for boolean Vars, since earlier phases of planning
will fold "boolvar = true" or "boolvar = false" to just "boolvar" or
"NOT boolvar" respectively.  Improve dependencies_clauselist_selectivity()
to recognize such clauses as equivalent to equality restrictions.

This fixes a failure of the extended stats mechanism to apply in a case
reported by Vitaliy Garnashevich.  It's not a complete solution to his
problem because the bitmap-scan costing code isn't consulting extended
stats where it should, but that's surely an independent issue.

In passing, improve some comments, get rid of a NumRelids() test that's
redundant with the preceding bms_membership() test, and fix
dependencies_clauselist_selectivity() so that estimatedclauses actually
is a pure output argument as stated by its API contract.

Back-patch to v10 where this code was introduced.

Discussion: https://postgr.es/m/73a4936d-2814-dc08-ed0c-978f76f435b0@gmail.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/ecc27d55f4c37a8485a7d0e1dae0eb5ef2bc886e

Modified Files
--------------
src/backend/statistics/dependencies.c | 110 +++++++++++++++++++---------------
1 file changed, 63 insertions(+), 47 deletions(-)


pgsql-committers by date:

Previous
From: Robert Haas
Date:
Subject: pgsql: Remove memory leak protection from Gather and Gather Mergenodes
Next
From: Andres Freund
Date:
Subject: Re: pgsql: Add some regression tests that exercise hash join code.