Horton

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

Peter Geoghegan <pg@bowt.ie>

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From: Peter Geoghegan <pg@bowt.ie>
To: Alena Rybakina <lena.ribackina@yandex.ru>
Cc: "Finnerty, Jim" <jfinnert@amazon.com>, Marcos Pegoraro <marcos@f10.com.br>, Alena Rybakina <a.rybakina@postgrespro.ru>, Andrey Lepikhov <a.lepikhov@postgrespro.ru>, pgsql-hackers@postgresql.org, teodor@sigaev.ru, Ranier Vilela <ranier.vf@gmail.com>, Tomas Vondra <tomas.vondra@enterprisedb.com>
Date: 2023-08-06T21:43:08Z
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 Sat, Aug 5, 2023 at 7:01 PM Peter Geoghegan <pg@bowt.ie> wrote:
> Of course this immediately makes me wonder: shouldn't your patch be
> able to perform an additional transformation here? You know, by
> transforming "a.x = 42 OR a.x = 44" into "a IN (42, 44)"? Although I
> haven't checked for myself, I assume that this doesn't happen right
> now, since your patch currently performs all of its transformations
> during parsing.

Many interesting cases won't get SAOP transformation from the patch,
simply because of the or_transform_limit GUC's default of 500. I don't
think that that design makes too much sense. It made more sense back
when the focus was on expression evaluation overhead. But that's only
one of the benefits that we now expect from the patch, right? So it
seems like something that should be revisited soon.

I'm not suggesting that there is no need for some kind of limit. But
it seems like a set of heuristics might be a better approach. Although
I would like to get a better sense of the costs of the transformation
to be able to say too much more.

-- 
Peter Geoghegan