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Fix finalization for json_objectagg and friends

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Commit f4fb45d15c misguidedly tried to free some state during aggregate
finalization for json_objectagg. This resulted in attempts to access
freed memory, especially when the function is used as a window function.
Commit 4eb9798879 attempted to ameliorate that, but in fact it should
just be ripped out, which is done here. Also add some regression tests
for json_objectagg in various flavors as a window function.

Original report from Jaime Casanova, diagnosis by Andres Freund.

Discussion: https://postgr.es/m/YkfeMNYRCGhySKyg@ahch-to
This commit is contained in:
Andrew Dunstan 2022-04-13 10:26:38 -04:00
parent a038679cd8
commit 112fdb3528
3 changed files with 53 additions and 12 deletions
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12
src/backend/utils/adt/json.c
View File

@ -1002,13 +1002,6 @@ json_unique_builder_init(JsonUniqueBuilderState *cxt)
cxt->skipped_keys.data = NULL;
}
static void
json_unique_builder_clean(JsonUniqueBuilderState *cxt)
{
if (cxt->skipped_keys.data)
resetStringInfo(&cxt->skipped_keys);
}
/* On-demand initialization of skipped_keys StringInfo structure */
static StringInfo
json_unique_builder_get_skipped_keys(JsonUniqueBuilderState *cxt)
@ -1216,8 +1209,6 @@ json_object_agg_finalfn(PG_FUNCTION_ARGS)
if (state == NULL)
PG_RETURN_NULL();
json_unique_builder_clean(&state->unique_check);
/* Else return state with appropriate object terminator added */
PG_RETURN_TEXT_P(catenate_stringinfo_string(state->str, " }"));
}
@ -1324,9 +1315,6 @@ json_build_object_worker(int nargs, Datum *args, bool *nulls, Oid *types,
appendStringInfoChar(result, '}');
if (unique_keys)
json_unique_builder_clean(&unique_check);
return PointerGetDatum(cstring_to_text_with_len(result->data, result->len));
}

35
src/test/regress/expected/sqljson.out
View File

@ -959,6 +959,41 @@ SELECT JSON_OBJECT('foo' : '1' FORMAT JSON, 'bar' : 'baz' RETURNING json);
CREATE OR REPLACE VIEW public.json_object_view AS
SELECT JSON_OBJECT('foo' : '1'::text FORMAT JSON, 'bar' : 'baz'::text RETURNING json) AS "json_object"
DROP VIEW json_object_view;
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v WITH UNIQUE KEYS) OVER (ORDER BY k)
FROM (VALUES (1,1), (2,2)) a(k,v);
a | json_objectagg
---------------+----------------------
{"k":1,"v":1} | { "1" : 1 }
{"k":2,"v":2} | { "1" : 1, "2" : 2 }
(2 rows)
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v WITH UNIQUE KEYS) OVER (ORDER BY k)
FROM (VALUES (1,1), (1,2), (2,2)) a(k,v);
ERROR: duplicate JSON key "1"
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v ABSENT ON NULL WITH UNIQUE KEYS)
OVER (ORDER BY k)
FROM (VALUES (1,1), (1,null), (2,2)) a(k,v);
ERROR: duplicate JSON key "1"
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v ABSENT ON NULL)
OVER (ORDER BY k)
FROM (VALUES (1,1), (1,null), (2,2)) a(k,v);
a | json_objectagg
------------------+----------------------
{"k":1,"v":1} | { "1" : 1 }
{"k":1,"v":null} | { "1" : 1 }
{"k":2,"v":2} | { "1" : 1, "2" : 2 }
(3 rows)
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v ABSENT ON NULL)
OVER (ORDER BY k RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
FROM (VALUES (1,1), (1,null), (2,2)) a(k,v);
a | json_objectagg
------------------+----------------------
{"k":1,"v":1} | { "1" : 1, "2" : 2 }
{"k":1,"v":null} | { "1" : 1, "2" : 2 }
{"k":2,"v":2} | { "1" : 1, "2" : 2 }
(3 rows)
-- Test JSON_ARRAY deparsing
EXPLAIN (VERBOSE, COSTS OFF)
SELECT JSON_ARRAY('1' FORMAT JSON, 2 RETURNING json);

18
src/test/regress/sql/sqljson.sql
View File

@ -292,6 +292,24 @@ SELECT JSON_OBJECT('foo' : '1' FORMAT JSON, 'bar' : 'baz' RETURNING json);
DROP VIEW json_object_view;
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v WITH UNIQUE KEYS) OVER (ORDER BY k)
FROM (VALUES (1,1), (2,2)) a(k,v);
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v WITH UNIQUE KEYS) OVER (ORDER BY k)
FROM (VALUES (1,1), (1,2), (2,2)) a(k,v);
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v ABSENT ON NULL WITH UNIQUE KEYS)
OVER (ORDER BY k)
FROM (VALUES (1,1), (1,null), (2,2)) a(k,v);
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v ABSENT ON NULL)
OVER (ORDER BY k)
FROM (VALUES (1,1), (1,null), (2,2)) a(k,v);
SELECT to_json(a) AS a, JSON_OBJECTAGG(k : v ABSENT ON NULL)
OVER (ORDER BY k RANGE BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING)
FROM (VALUES (1,1), (1,null), (2,2)) a(k,v);
-- Test JSON_ARRAY deparsing
EXPLAIN (VERBOSE, COSTS OFF)
SELECT JSON_ARRAY('1' FORMAT JSON, 2 RETURNING json);