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Commitda0d8a4

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Ensure casting to typmod -1 generates a RelabelType.
Fix the code changed by commit5c056b0 so that we always generateRelabelType, not something else, for a cast to unspecified typmod.Otherwise planner optimizations might not happen.It appears we missed this point because the previous experiments weredone on type numeric: the parser undesirably generates a call on thenumeric() length-coercion function, but then numeric_support()optimizes that down to a RelabelType, so that everything seems fine.It misbehaves for types that have a non-optimized length coercionfunction, such as bpchar.Per report from John Naylor. Back-patch to all supported branches,as the previous patch eventually was. Unfortunately, that no longerincludes 9.6 ... we really shouldn't put this type of change into anearly-EOL branch.Discussion:https://postgr.es/m/CAFBsxsEfbFHEkouc+FSj+3K1sHipLPbEC67L0SAe-9-da8QtYg@mail.gmail.com
1 parentaadbf82 commitda0d8a4

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‎src/backend/parser/parse_coerce.c‎

Lines changed: 9 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -763,7 +763,15 @@ coerce_type_typmod(Node *node, Oid targetTypeId, int32 targetTypMod,
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if (hideInputCoercion)
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hide_coercion_node(node);
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pathtype=find_typmod_coercion_function(targetTypeId,&funcId);
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/*
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* A negative typmod means that no actual coercion is needed, but we still
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* want a RelabelType to ensure that the expression exposes the intended
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* typmod.
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*/
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if (targetTypMod<0)
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pathtype=COERCION_PATH_NONE;
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else
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pathtype=find_typmod_coercion_function(targetTypeId,&funcId);
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if (pathtype!=COERCION_PATH_NONE)
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{

‎src/test/regress/expected/expressions.out‎

Lines changed: 36 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -194,4 +194,40 @@ explain (verbose, costs off) select * from numeric_view;
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Output: numeric_tbl.f1, (numeric_tbl.f1)::numeric(16,4), (numeric_tbl.f1)::numeric, numeric_tbl.f2, (numeric_tbl.f2)::numeric(16,4), numeric_tbl.f2
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(2 rows)
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-- bpchar, lacking planner support for its length coercion function,
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-- could behave differently
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create table bpchar_tbl (f1 character(16) unique, f2 bpchar);
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create view bpchar_view as
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select
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f1, f1::character(14) as f114, f1::bpchar as f1n,
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f2, f2::character(14) as f214, f2::bpchar as f2n
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from bpchar_tbl;
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\d+ bpchar_view
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View "public.bpchar_view"
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Column | Type | Collation | Nullable | Default | Storage | Description
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--------+---------------+-----------+----------+---------+----------+-------------
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f1 | character(16) | | | | extended |
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f114 | character(14) | | | | extended |
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f1n | bpchar | | | | extended |
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f2 | bpchar | | | | extended |
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f214 | character(14) | | | | extended |
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f2n | bpchar | | | | extended |
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View definition:
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SELECT bpchar_tbl.f1,
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bpchar_tbl.f1::character(14) AS f114,
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bpchar_tbl.f1::bpchar AS f1n,
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bpchar_tbl.f2,
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bpchar_tbl.f2::character(14) AS f214,
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bpchar_tbl.f2 AS f2n
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FROM bpchar_tbl;
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explain (verbose, costs off) select * from bpchar_view
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where f1::bpchar = 'foo';
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QUERY PLAN
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------------------------------------------------------------------------------------------------------------------------------------------------
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Index Scan using bpchar_tbl_f1_key on public.bpchar_tbl
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Output: bpchar_tbl.f1, (bpchar_tbl.f1)::character(14), (bpchar_tbl.f1)::bpchar, bpchar_tbl.f2, (bpchar_tbl.f2)::character(14), bpchar_tbl.f2
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Index Cond: ((bpchar_tbl.f1)::bpchar = 'foo'::bpchar)
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(3 rows)
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rollback;

‎src/test/regress/sql/expressions.sql‎

Lines changed: 16 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -84,4 +84,20 @@ create view numeric_view as
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explain (verbose, costs off)select*from numeric_view;
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-- bpchar, lacking planner support for its length coercion function,
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-- could behave differently
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createtablebpchar_tbl (f1 character(16) unique, f2 bpchar);
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createviewbpchar_viewas
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select
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f1, f1::character(14)as f114, f1::bpcharas f1n,
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f2, f2::character(14)as f214, f2::bpcharas f2n
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from bpchar_tbl;
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\d+ bpchar_view
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explain (verbose, costs off)select*from bpchar_view
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where f1::bpchar='foo';
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rollback;

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