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Fix asymmetry in setting EquivalenceClass.ec_sortref

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0452b461bc made get_eclass_for_sort_expr() always set
EquivalenceClass.ec_sortref if it's not done yet.  This leads to an asymmetric
situation when whoever first looks for the EquivalenceClass sets the
ec_sortref.  It is also counterintuitive that get_eclass_for_sort_expr()
performs modification of data structures.

This commit makes make_pathkeys_for_sortclauses_extended() responsible for
setting EquivalenceClass.ec_sortref.  Now we set the
EquivalenceClass.ec_sortref's needed to explore alternative GROUP BY ordering
specifically during building pathkeys by the list of grouping clauses.

Discussion: https://postgr.es/m/17037754-f187-4138-8285-0e2bfebd0dea%40postgrespro.ru
Reported-by: Tom Lane
Author: Andrei Lepikhov
Reviewed-by: Alexander Korotkov, Pavel Borisov
This commit is contained in:
Alexander Korotkov
2024-06-06 13:41:34 +03:00
parent f654f000dd
commit 199012a3d8
6 changed files with 92 additions and 19 deletions
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13
src/backend/optimizer/path/equivclass.c
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@@ -652,18 +652,7 @@ get_eclass_for_sort_expr(PlannerInfo *root,
if (opcintype == cur_em->em_datatype &&
equal(expr, cur_em->em_expr))
{
/*
* Match!
*
* Copy the sortref if it wasn't set yet. That may happen if
* the ec was constructed from a WHERE clause, i.e. it doesn't
* have a target reference at all.
*/
if (cur_ec->ec_sortref == 0 && sortref > 0)
cur_ec->ec_sortref = sortref;
return cur_ec;
}
return cur_ec; /* Match! */
}
}