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SQL/JSON: Fix some oversights in commit b6e1157e7

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The decision in b6e1157e7 to ignore raw_expr when evaluating a
JsonValueExpr was incorrect.  While its value is not ultimately
used (since formatted_expr's value is), failing to initialize it
can lead to problems, for instance,  when the expression tree in
raw_expr contains Aggref nodes, which must be initialized to
ensure the parent Agg node works correctly.

Also, optimize eval_const_expressions_mutator()'s handling of
JsonValueExpr a bit.  Currently, when formatted_expr cannot be folded
into a constant, we end up processing it twice -- once directly in
eval_const_expressions_mutator() and again recursively via
ece_generic_processing().  This recursive processing is required to
handle raw_expr. To avoid the redundant processing of formatted_expr,
we now  process raw_expr directly in eval_const_expressions_mutator().

Finally, update the comment of JsonValueExpr to describe the roles of
raw_expr and formatted_expr more clearly.

Bug: #18657
Reported-by: Alexander Lakhin <exclusion@gmail.com>
Diagnosed-by: Fabio R. Sluzala <fabio3rs@gmail.com>
Diagnosed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Tom Lane <tgl@sss.pgh.pa.us>
Discussion: https://postgr.es/m/18657-1b90ccce2b16bdb8@postgresql.org
Backpatch-through: 16
This commit is contained in:
Amit Langote
2024-10-20 12:21:03 +09:00
parent 0f4045814f
commit fa4f11854c
5 changed files with 92 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

2
src/backend/executor/execExpr.c
View File

@@ -2294,6 +2294,8 @@ ExecInitExprRec(Expr *node, ExprState *state,
{
JsonValueExpr *jve = (JsonValueExpr *) node;
Assert(jve->raw_expr != NULL);
ExecInitExprRec(jve->raw_expr, state, resv, resnull);
Assert(jve->formatted_expr != NULL);
ExecInitExprRec(jve->formatted_expr, state, resv, resnull);
break;

22
src/backend/optimizer/util/clauses.c
View File

@@ -2897,13 +2897,25 @@ eval_const_expressions_mutator(Node *node,
case T_JsonValueExpr:
{
JsonValueExpr *jve = (JsonValueExpr *) node;
Node *formatted;
Node *raw_expr = (Node *) jve->raw_expr;
Node *formatted_expr = (Node *) jve->formatted_expr;
formatted = eval_const_expressions_mutator((Node *) jve->formatted_expr,
/*
* If we can fold formatted_expr to a constant, we can elide
* the JsonValueExpr altogether. Otherwise we must process
* raw_expr too. But JsonFormat is a flat node and requires
* no simplification, only copying.
*/
formatted_expr = eval_const_expressions_mutator(formatted_expr,
context);
if (formatted && IsA(formatted, Const))
return formatted;
break;
if (formatted_expr && IsA(formatted_expr, Const))
return formatted_expr;
raw_expr = eval_const_expressions_mutator(raw_expr, context);
return (Node *) makeJsonValueExpr((Expr *) raw_expr,
(Expr *) formatted_expr,
copyObject(jve->format));
}
case T_SubPlan:

14
src/include/nodes/primnodes.h
View File

@@ -1596,15 +1596,19 @@ typedef struct JsonReturning
* JsonValueExpr -
* representation of JSON value expression (expr [FORMAT JsonFormat])
*
* The actual value is obtained by evaluating formatted_expr. raw_expr is
* only there for displaying the original user-written expression and is not
* evaluated by ExecInterpExpr() and eval_const_exprs_mutator().
* raw_expr is the user-specified value, while formatted_expr is the value
* obtained by coercing raw_expr to the type required by either the FORMAT
* clause or an enclosing node's RETURNING clause.
*
* When deparsing a JsonValueExpr, get_rule_expr() prints raw_expr. However,
* during the evaluation of a JsonValueExpr, the value of formatted_expr
* takes precedence over that of raw_expr.
*/
typedef struct JsonValueExpr
{
NodeTag type;
Expr *raw_expr; /* raw expression */
Expr *formatted_expr; /* formatted expression */
Expr *raw_expr; /* user-specified expression */
Expr *formatted_expr; /* coerced formatted expression */
JsonFormat *format; /* FORMAT clause, if specified */
} JsonValueExpr;

49
src/test/regress/expected/sqljson.out
View File

@@ -951,3 +951,52 @@ CREATE OR REPLACE VIEW public.is_json_view AS
'{}'::text IS JSON OBJECT WITH UNIQUE KEYS AS object
FROM generate_series(1, 3) i(i)
DROP VIEW is_json_view;
-- Bug #18657: JsonValueExpr.raw_expr was not initialized in ExecInitExprRec()
-- causing the Aggrefs contained in it to also not be initialized, which led
-- to a crash in ExecBuildAggTrans() as mentioned in the bug report:
-- https://postgr.es/m/18657-1b90ccce2b16bdb8@postgresql.org
CREATE FUNCTION volatile_one() RETURNS int AS $$ BEGIN RETURN 1; END; $$ LANGUAGE plpgsql VOLATILE;
CREATE FUNCTION stable_one() RETURNS int AS $$ BEGIN RETURN 1; END; $$ LANGUAGE plpgsql STABLE;
EXPLAIN (VERBOSE, COSTS OFF) SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': volatile_one() RETURNING text) FORMAT JSON);
QUERY PLAN
-------------------------------------------------------------------------------------------------------------
Aggregate
Output: JSON_OBJECT('a' : JSON_OBJECTAGG('b' : volatile_one() RETURNING text) FORMAT JSON RETURNING json)
-> Result
(3 rows)
SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': volatile_one() RETURNING text) FORMAT JSON);
json_object
---------------------
{"a" : { "b" : 1 }}
(1 row)
EXPLAIN (VERBOSE, COSTS OFF) SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': stable_one() RETURNING text) FORMAT JSON);
QUERY PLAN
-----------------------------------------------------------------------------------------------------------
Aggregate
Output: JSON_OBJECT('a' : JSON_OBJECTAGG('b' : stable_one() RETURNING text) FORMAT JSON RETURNING json)
-> Result
(3 rows)
SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': stable_one() RETURNING text) FORMAT JSON);
json_object
---------------------
{"a" : { "b" : 1 }}
(1 row)
EXPLAIN (VERBOSE, COSTS OFF) SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': 1 RETURNING text) FORMAT JSON);
QUERY PLAN
------------------------------------------------------------------------------------------------
Aggregate
Output: JSON_OBJECT('a' : JSON_OBJECTAGG('b' : 1 RETURNING text) FORMAT JSON RETURNING json)
-> Result
(3 rows)
SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': 1 RETURNING text) FORMAT JSON);
json_object
---------------------
{"a" : { "b" : 1 }}
(1 row)
DROP FUNCTION volatile_one, stable_one;

14
src/test/regress/sql/sqljson.sql
View File

@@ -383,3 +383,17 @@ SELECT '1' IS JSON AS "any", ('1' || i) IS JSON SCALAR AS "scalar", '[]' IS NOT
\sv is_json_view
DROP VIEW is_json_view;
-- Bug #18657: JsonValueExpr.raw_expr was not initialized in ExecInitExprRec()
-- causing the Aggrefs contained in it to also not be initialized, which led
-- to a crash in ExecBuildAggTrans() as mentioned in the bug report:
-- https://postgr.es/m/18657-1b90ccce2b16bdb8@postgresql.org
CREATE FUNCTION volatile_one() RETURNS int AS $$ BEGIN RETURN 1; END; $$ LANGUAGE plpgsql VOLATILE;
CREATE FUNCTION stable_one() RETURNS int AS $$ BEGIN RETURN 1; END; $$ LANGUAGE plpgsql STABLE;
EXPLAIN (VERBOSE, COSTS OFF) SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': volatile_one() RETURNING text) FORMAT JSON);
SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': volatile_one() RETURNING text) FORMAT JSON);
EXPLAIN (VERBOSE, COSTS OFF) SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': stable_one() RETURNING text) FORMAT JSON);
SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': stable_one() RETURNING text) FORMAT JSON);
EXPLAIN (VERBOSE, COSTS OFF) SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': 1 RETURNING text) FORMAT JSON);
SELECT JSON_OBJECT('a': JSON_OBJECTAGG('b': 1 RETURNING text) FORMAT JSON);
DROP FUNCTION volatile_one, stable_one;