Return NULL from json_object_agg if it gets no rows.

This makes it consistent with the docs and with all other builtin
aggregates apart from count().

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 494a0285267a542582c8129a40fe551e2128cdb2..1820029fe956d68d28678826dfc0d33097245660 100644 (file)
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -1973,7 +1973,7 @@ json_object_agg_finalfn(PG_FUNCTION_ARGS)
        state = PG_ARGISNULL(0) ? NULL : (StringInfo) PG_GETARG_POINTER(0);
 
        if (state == NULL)
-               PG_RETURN_TEXT_P(cstring_to_text("{}"));
+               PG_RETURN_NULL();
 
        appendStringInfoString(state, " }");