Horton

Re: Performance issue in foreign-key-aware join estimation

David Rowley <david.rowley@2ndquadrant.com>

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From: David Rowley <david.rowley@2ndquadrant.com>
To: Andreas Seltenreich <seltenreich@gmx.de>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, Tomas Vondra <tomas.vondra@2ndquadrant.com>
Date: 2019-07-21T13:50:35Z
Lists: pgsql-hackers 
On Mon, 22 Jul 2019 at 00:44, Andreas Seltenreich <seltenreich@gmx.de> wrote:
> sqlsmith triggers an assertion in this commit (3373c7155350):
>
> TRAP: FailedAssertion("!(rel->reloptkind == RELOPT_BASEREL)", File: "equivclass.c", Line: 764)

Thanks for the report.

It looks like this is caused by the join removal code removing the
LEFT JOIN and leaving a dead rel in the eclasses ec_relids.  The fix
is likely either to adjust the Assert to allow that or to add an if
test so that we only bother calling bms_add_member for base rels.  I'm
not quite sure yet.

-- 
 David Rowley                   http://www.2ndQuadrant.com/
 PostgreSQL Development, 24x7 Support, Training & Services

Commits

  1. Adjust overly strict Assert

  2. Speed up finding EquivalenceClasses for a given set of rels

  3. Speed up match_eclasses_to_foreign_key_col() when there are many ECs.