Horton

Re: POC, WIP: OR-clause support for indexes

Peter Geoghegan <pg@bowt.ie>

View thread
From: Peter Geoghegan <pg@bowt.ie>
To: Robert Haas <robertmhaas@gmail.com>
Cc: Alexander Korotkov <aekorotkov@gmail.com>, Tom Lane <tgl@sss.pgh.pa.us>, Alena Rybakina <a.rybakina@postgrespro.ru>, jian he <jian.universality@gmail.com>, Nikolay Shaplov <dhyan@nataraj.su>, pgsql-hackers@lists.postgresql.org, pgsql-hackers@postgresql.org, Marcos Pegoraro <marcos@f10.com.br>, teodor@sigaev.ru, Peter Eisentraut <peter@eisentraut.org>, Ranier Vilela <ranier.vf@gmail.com>, Andrei Lepikhov <lepihov@gmail.com>
Date: 2024-10-04T16:45:52Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Make group_similar_or_args() reorder clause list as little as possible

  2. Allow usage of match_orclause_to_indexcol() for joins

  3. Skip not SOAP-supported indexes while transforming an OR clause into SAOP

  4. Remove the wrong assertion from match_orclause_to_indexcol()

  5. Teach bitmap path generation about transforming OR-clauses to SAOP's

  6. Transform OR-clauses to SAOP's during index matching

  7. Fix the value of or_to_any_transform_limit in postgresql.conf.sample

  8. Transform OR clauses to ANY expression

  9. MergeAttributes code deduplication

  10. SEARCH and CYCLE clauses

  11. Improve estimation of OR clauses using extended statistics.

  12. Teach btree to handle ScalarArrayOpExpr quals natively.

  13. Revise collation derivation method and expression-tree representation.

  14. Instead of trying to force WHERE clauses into CNF or DNF normal form,

On Fri, Oct 4, 2024 at 10:24 AM Robert Haas <robertmhaas@gmail.com> wrote:
> Interesting. I would not have guessed that. I wonder how it works.

ISTM that we've established a general expectation that you as a user
can be fairly imprecise about which specific types you use as
constants in your query, while still getting an index scan (provided
all of the types involved have opclasses that are part of the same
opfamily, and that the index uses one of those opclasses as its input
opclass). Imagine how confusing it would be if "SELECT * FROM
pgbench_accounts WHERE aid = 5" didn't get an index scan whenever the
"aid" column happened to be bigint -- that would be totally
unacceptable. The main reason why we have operator classes that are
grouped into opfamilies is to allow the optimizer to understand the
relationship between opclasses sufficient to enable this flexibility.

It's concerning that there's a performance cliff with the patch
whenever one of the constants is changed from (say) 2_147_483_647 to
2_147_483_648 -- who will even notice that they've actually mixed two
different types of integers here? Users certainly won't see any
similar problems in the simple "Var = Const" case, nor will they see
problems in the mixed-type IN() list case.

-- 
Peter Geoghegan