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: Alexander Korotkov <aekorotkov@gmail.com>
Cc: Andrei Lepikhov <lepihov@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, Robert Haas <robertmhaas@gmail.com>, pgsql-hackers@postgresql.org, Marcos Pegoraro <marcos@f10.com.br>, teodor@sigaev.ru, Peter Eisentraut <peter@eisentraut.org>, Ranier Vilela <ranier.vf@gmail.com>
Date: 2024-10-04T17:43:52Z
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 7:45 AM Alexander Korotkov <aekorotkov@gmail.com> wrote:
> Andrei, thank you for your opinion.  Just for the record, I'm still
> exploring this and will reply later today or tomorrow.

The logic that allows this to work for the case of IN() lists appears
in transformAExprIn(), which is in parse_expr.c. I wonder if it would
be possible to do something similar at the point where the patch does
its conversion to a SAOP. What do you think?

The transformAExprIn() logic doesn't directly care about operator
families. It works by using coercions, which opfamily authors are
formally required to promise cannot affect sort order. According to
the sgml docs: "Another requirement for a multiple-data-type family is
that any implicit or binary-coercion casts that are defined between
data types included in the operator family must not change the
associated sort ordering".

This logic seems to always do the right thing for cases like my IN()
test case from today, which should have an array of the type of the
widest integer type from btree/integer_ops (so a bigint[] SAOP for
that specific test case). There won't ever be a "cannot coerce to
common array type" error because logic in select_common_type() aims to
choose a common array type that every individual expression can be
implicitly cast to. It can fail to identify a common type, but AFAICT
only in cases where that actually makes sense.

-- 
Peter Geoghegan