From 7dce02a462eff7492befcaa9fa27062816780e7d Mon Sep 17 00:00:00 2001 From: Andrey Rachitskiy Date: Fri, 28 Aug 2026 12:33:47 +0500 Subject: [PATCH v3] Fold immutable XmlExpr forms in eval_const_expressions IS DOCUMENT was left as XmlExpr even with a Const argument, so CASE still simplified unused WHEN results and could execute xpath() during planning. That started failing for SQL-language functions once they began using custom plans. Fold XmlExpr in eval_const_expressions when all inputs are Const and the op is immutable. Treat XMLELEMENT and XMLFOREST as non-immutable. Other XmlExprOps only manipulate xml/text. Bug: #19487 Author: Andrey Rachitskiy Reported-by: Ilya Portnov Reviewed-by: Tom Lane Discussion: https://www.postgresql.org/message-id/19487-367258bc497b923a%40postgresql.org Backpatch-through: 18 --- src/backend/optimizer/util/clauses.c | 37 ++++++++++++++++++++++++++++ src/test/regress/expected/xml.out | 10 ++++++++ src/test/regress/sql/xml.sql | 5 ++++ 3 files changed, 52 insertions(+) diff --git a/src/backend/optimizer/util/clauses.c b/src/backend/optimizer/util/clauses.c index 8da4ed617b5..96153179668 100644 --- a/src/backend/optimizer/util/clauses.c +++ b/src/backend/optimizer/util/clauses.c @@ -115,6 +115,7 @@ static bool contain_agg_clause_walker(Node *node, void *context); static bool find_window_functions_walker(Node *node, WindowFuncLists *lists); static bool contain_subplans_walker(Node *node, void *context); static bool contain_mutable_functions_walker(Node *node, void *context); +static bool xmlexpr_is_immutable(XmlExpr *xexpr); static bool contain_volatile_functions_walker(Node *node, void *context); static bool contain_volatile_functions_not_nextval_walker(Node *node, void *context); static bool max_parallel_hazard_walker(Node *node, @@ -496,6 +497,34 @@ contain_mutable_functions_walker(Node *node, void *context) context); } +/* + * xmlexpr_is_immutable + * True if this XmlExpr is immutable. + * + * XMLELEMENT and XMLFOREST are treated as non-immutable. Other XmlExprOps + * only manipulate xml/text. + */ +static bool +xmlexpr_is_immutable(XmlExpr *xexpr) +{ + switch (xexpr->op) + { + case IS_XMLCONCAT: + case IS_XMLPARSE: + case IS_XMLPI: + case IS_XMLROOT: + case IS_XMLSERIALIZE: + case IS_DOCUMENT: + return true; + + case IS_XMLELEMENT: + case IS_XMLFOREST: + return false; + } + + return false; +} + /* * contain_mutable_functions_after_planning * Test whether given expression contains mutable functions. @@ -3702,6 +3731,14 @@ eval_const_expressions_mutator(Node *node, return ece_evaluate_expr(node); return node; } + case T_XmlExpr: + { + node = ece_generic_processing(node); + if (ece_all_arguments_const(node) && + xmlexpr_is_immutable((XmlExpr *) node)) + return ece_evaluate_expr(node); + return node; + } case T_CoalesceExpr: { CoalesceExpr *coalesceexpr = (CoalesceExpr *) node; diff --git a/src/test/regress/expected/xml.out b/src/test/regress/expected/xml.out index fb3e0ec41b2..d60e1c4efb7 100644 --- a/src/test/regress/expected/xml.out +++ b/src/test/regress/expected/xml.out @@ -713,6 +713,16 @@ LINE 1: SELECT '<>' IS NOT DOCUMENT; DETAIL: line 1: StartTag: invalid element name <> ^ +-- Fold IS DOCUMENT so CASE does not simplify unused xpath() at plan time. +SELECT CASE WHEN ('2019-12-16T00:00:00.000'::xml) IS DOCUMENT + THEN (xpath('/*/text()', '2019-12-16T00:00:00.000'::xml))[1]::text + ELSE ('2019-12-16T00:00:00.000'::xml)::text +END; + case +------------------------- + 2019-12-16T00:00:00.000 +(1 row) + SELECT xmlagg(data) FROM xmltest; xmlagg -------------------------------------- diff --git a/src/test/regress/sql/xml.sql b/src/test/regress/sql/xml.sql index aafd39433a6..52e39187447 100644 --- a/src/test/regress/sql/xml.sql +++ b/src/test/regress/sql/xml.sql @@ -185,6 +185,11 @@ SELECT xml '' IS NOT DOCUMENT; SELECT xml 'abc' IS NOT DOCUMENT; SELECT '<>' IS NOT DOCUMENT; +-- Fold IS DOCUMENT so CASE does not simplify unused xpath() at plan time. +SELECT CASE WHEN ('2019-12-16T00:00:00.000'::xml) IS DOCUMENT + THEN (xpath('/*/text()', '2019-12-16T00:00:00.000'::xml))[1]::text + ELSE ('2019-12-16T00:00:00.000'::xml)::text +END; SELECT xmlagg(data) FROM xmltest; SELECT xmlagg(data) FROM xmltest WHERE id > 10; -- 2.53.0