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Don't let JSON constructor coercions block SQL function inlining

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contain_context_dependent_node_walker() reports a CaseTestExpr as
context-dependent unless it sits under a simple CaseExpr or the
elemexpr of an ArrayCoerceExpr.  A JsonConstructorExpr whose RETURNING
type requires a coercion also carries a CaseTestExpr placeholder in
that coercion, so any SQL function called with such a constructor as
an argument was refused inlining.

Teach the walker that a CaseTestExpr is expected within the coercion
of a JsonConstructorExpr, the same way it already handles the elemexpr
of an ArrayCoerceExpr.  This is safe now that eval_const_expressions
no longer lets an enclosing simple CASE clobber that placeholder.

Author: Richard Guo <guofenglinux@gmail.com>
Discussion: https://postgr.es/m/CAMbWs48A=VCFbteTkuCoknO1_0-Cu0aMBT0M07dm7vj1QyixDg@mail.gmail.com
Backpatch-through: 19
This commit is contained in:
Richard Guo
2026-09-14 17:04:13 +09:00
parent e17df18a81
commit 9d0adee876
3 changed files with 48 additions and 1 deletions
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23
src/backend/optimizer/util/clauses.c
View File

@@ -1255,7 +1255,8 @@ contain_exec_param_walker(Node *node, List *param_ids)
* not nested within another one, or they'll see the wrong test value. If one
* appears "bare" in the arguments of a SQL function, then we can't inline the
* SQL function for fear of creating such a situation. The same applies for
* CaseTestExpr used within the elemexpr of an ArrayCoerceExpr.
* CaseTestExpr used within the elemexpr of an ArrayCoerceExpr or the coercion
* of a JsonConstructorExpr.
*
* CoerceToDomainValue would have the same issue if domain CHECK expressions
* could get inlined into larger expressions, but presently that's impossible.
@@ -1328,6 +1329,26 @@ contain_context_dependent_node_walker(Node *node, int *flags)
*flags = save_flags;
return res;
}
else if (IsA(node, JsonConstructorExpr))
{
JsonConstructorExpr *jce = (JsonConstructorExpr *) node;
int save_flags;
bool res;
/* Check the args and func expressions */
if (contain_context_dependent_node_walker((Node *) jce->args, flags))
return true;
if (contain_context_dependent_node_walker((Node *) jce->func, flags))
return true;
/* Check the coercion, which is allowed to contain CaseTestExpr */
save_flags = *flags;
*flags |= CCDN_CASETESTEXPR_OK;
res = contain_context_dependent_node_walker((Node *) jce->coercion,
flags);
*flags = save_flags;
return res;
}
return expression_tree_walker(node, contain_context_dependent_node_walker,
flags);
}

18
src/test/regress/expected/sqljson.out
View File

@@ -580,6 +580,24 @@ SELECT CASE 'x' WHEN JSON_OBJECT('a': 'b' RETURNING text) THEN 1 ELSE 0 END;
0
(1 row)
-- the RETURNING coercion must not prevent inlining of a SQL function
CREATE FUNCTION json_object_inline_test(text) RETURNS text
LANGUAGE sql IMMUTABLE AS $$ SELECT $1 || '!' $$;
EXPLAIN (VERBOSE, COSTS OFF)
SELECT json_object_inline_test(JSON_OBJECT('a': 'b' RETURNING text));
QUERY PLAN
----------------------------------------------------------------------
Result
Output: (JSON_OBJECT('a' : 'b'::text RETURNING text) || '!'::text)
(2 rows)
SELECT json_object_inline_test(JSON_OBJECT('a': 'b' RETURNING text));
json_object_inline_test
-------------------------
{"a" : "b"}!
(1 row)
DROP FUNCTION json_object_inline_test(text);
-- BUG: https://postgr.es/m/CADXhmgTJtJZK9A3Na_ry%2BXrq-ghjcejBRhcRMzWZvbd__QdgJA%40mail.gmail.com
-- datum_to_jsonb_internal() didn't catch keys that are casts instead of a simple scalar
CREATE TYPE mood AS ENUM ('happy', 'sad', 'neutral');

8
src/test/regress/sql/sqljson.sql
View File

@@ -155,6 +155,14 @@ SELECT JSON_OBJECT(1: 1, '2': NULL, '3': 1, 4: NULL, '5': 'a' ABSENT ON NULL WIT
-- the RETURNING coercion must not pick up the test value of an enclosing CASE
SELECT CASE 'x' WHEN JSON_OBJECT('a': 'b' RETURNING text) THEN 1 ELSE 0 END;
-- the RETURNING coercion must not prevent inlining of a SQL function
CREATE FUNCTION json_object_inline_test(text) RETURNS text
LANGUAGE sql IMMUTABLE AS $$ SELECT $1 || '!' $$;
EXPLAIN (VERBOSE, COSTS OFF)
SELECT json_object_inline_test(JSON_OBJECT('a': 'b' RETURNING text));
SELECT json_object_inline_test(JSON_OBJECT('a': 'b' RETURNING text));
DROP FUNCTION json_object_inline_test(text);
-- BUG: https://postgr.es/m/CADXhmgTJtJZK9A3Na_ry%2BXrq-ghjcejBRhcRMzWZvbd__QdgJA%40mail.gmail.com
-- datum_to_jsonb_internal() didn't catch keys that are casts instead of a simple scalar
CREATE TYPE mood AS ENUM ('happy', 'sad', 'neutral');