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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
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@@ -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));
}