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Commita11b3bd

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Fix misprocessing of equivalence classes involving record_eq().
canonicalize_ec_expression() is supposed to agree with coerce_type() as towhether a RelabelType should be inserted to make a subexpression be validinput for the operators of a given opclass. However, it did the wrongthing with named-composite-type inputs to record_eq(): it put in aRelabelType to RECORDOID, which the parser doesn't. In some cases this washarmless because all code paths involving a particular equivalence classdid the same thing, but in other cases this would result in failing torecognize a composite-type expression as being a member of an equivalenceclass that it actually is a member of. The most obvious bad effect was tofail to recognize that an index on a composite column could provide thesort order needed for a mergejoin on that column, as reported by TeodorSigaev. I think there might be other, subtler, cases that result inmisoptimization. It also seems possible that an unwanted RelabelTypewould sometimes get into an emitted plan --- but because record_eq andfriends don't examine the declared type of their input expressions, thatwould not create any visible problems.To fix, just treat RECORDOID as if it were a polymorphic type, which insome sense it is. We might want to consider formalizing that a bit moresomeday, but for the moment this seems to be the only place where anIsPolymorphicType() test ought to include RECORDOID as well.This has been broken for a long time, so back-patch to all supportedbranches.Discussion:https://postgr.es/m/a6b22369-e3bf-4d49-f59d-0c41d3551e81@sigaev.ru
1 parent7fc7dac commita11b3bd

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3 files changed

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lines changed

3 files changed

+52
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lines changed

‎src/backend/optimizer/path/equivclass.c

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@@ -497,8 +497,9 @@ canonicalize_ec_expression(Expr *expr, Oid req_type, Oid req_collation)
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/*
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* For a polymorphic-input-type opclass, just keep the same exposed type.
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* RECORD opclasses work like polymorphic-type ones for this purpose.
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*/
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if (IsPolymorphicType(req_type))
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if (IsPolymorphicType(req_type)||req_type==RECORDOID)
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req_type=expr_type;
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/*

‎src/test/regress/expected/join.out

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@@ -2672,6 +2672,36 @@ select * from a left join b on i = x and i = y and x = i;
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---+---+---
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(0 rows)
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rollback;
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--
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-- test handling of merge clauses using record_ops
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--
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begin;
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create type mycomptype as (id int, v bigint);
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create temp table tidv (idv mycomptype);
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create index on tidv (idv);
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explain (costs off)
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select a.idv, b.idv from tidv a, tidv b where a.idv = b.idv;
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QUERY PLAN
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----------------------------------------------------------
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Merge Join
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Merge Cond: (a.idv = b.idv)
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-> Index Only Scan using tidv_idv_idx on tidv a
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-> Materialize
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-> Index Only Scan using tidv_idv_idx on tidv b
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(5 rows)
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set enable_mergejoin = 0;
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explain (costs off)
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select a.idv, b.idv from tidv a, tidv b where a.idv = b.idv;
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QUERY PLAN
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----------------------------------------------------
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Nested Loop
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-> Seq Scan on tidv a
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-> Index Only Scan using tidv_idv_idx on tidv b
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Index Cond: (idv = a.idv)
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(4 rows)
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rollback;
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--
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-- test NULL behavior of whole-row Vars, per bug #5025

‎src/test/regress/sql/join.sql

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Original file line numberDiff line numberDiff line change
@@ -673,6 +673,26 @@ select * from a left join b on i = x and i = y and x = i;
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rollback;
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--
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-- test handling of merge clauses using record_ops
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--
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begin;
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createtypemycomptypeas (idint, vbigint);
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create temp table tidv (idv mycomptype);
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createindexon tidv (idv);
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explain (costs off)
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selecta.idv,b.idvfrom tidv a, tidv bwherea.idv=b.idv;
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set enable_mergejoin=0;
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explain (costs off)
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selecta.idv,b.idvfrom tidv a, tidv bwherea.idv=b.idv;
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rollback;
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--
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-- test NULL behavior of whole-row Vars, per bug #5025
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--

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