pg_stat_get_backend_idset should reset fmgr_info->fn_extra at end of

execution, so that it restarts correctly if query tree is used again.

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 23617b850753a86cfa1430b2f456d8d4952ff951..01cc5e45b399ab17d9aaccf27cd834f95836406f 100644 (file)
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -179,33 +179,29 @@ Datum
 pg_stat_get_backend_idset(PG_FUNCTION_ARGS)
 {
        FmgrInfo           *fmgr_info = fcinfo->flinfo;
-       MemoryContext   oldcxt;
        int32                   result;
 
-       if (fcinfo->resultinfo == NULL)
-               elog(ERROR, "called in context that does not accept a set result (1)");
-       if (!IsA(fcinfo->resultinfo, ReturnSetInfo))
-               elog(ERROR, "called in context that does not accept a set result (2)");
+       if (fcinfo->resultinfo == NULL ||
+               !IsA(fcinfo->resultinfo, ReturnSetInfo))
+               elog(ERROR, "pg_stat_get_backend_idset: called in context that does not accept a set result");
 
        if (fmgr_info->fn_extra == NULL)
        {
                if (fmgr_info->fn_mcxt == NULL)
                        elog(ERROR, "No function memory context in set-function");
-
-               oldcxt = MemoryContextSwitchTo(fmgr_info->fn_mcxt);
-               fmgr_info->fn_extra = palloc(sizeof(int32) * 2);
-               ((int32 *)(fmgr_info->fn_extra))[0] = 0;
-               ((int32 *)(fmgr_info->fn_extra))[1] = 
-                                               (int32)pgstat_fetch_stat_numbackends();
-               MemoryContextSwitchTo(oldcxt);
+               fmgr_info->fn_extra = MemoryContextAlloc(fmgr_info->fn_mcxt,
+                                                                                                2 * sizeof(int));
+               ((int *)(fmgr_info->fn_extra))[0] = 0;
+               ((int *)(fmgr_info->fn_extra))[1] = pgstat_fetch_stat_numbackends();
        }
 
-       ((int32 *)(fmgr_info->fn_extra))[0] += 1;
-       result = ((int32 *)(fmgr_info->fn_extra))[0];
-
+       ((int *)(fmgr_info->fn_extra))[0] += 1;
+       result = ((int *)(fmgr_info->fn_extra))[0];
 
-       if (result > ((int32 *)(fmgr_info->fn_extra))[1])
+       if (result > ((int *)(fmgr_info->fn_extra))[1])
        {
+               pfree(fmgr_info->fn_extra);
+               fmgr_info->fn_extra = NULL;
                ((ReturnSetInfo *)(fcinfo->resultinfo))->isDone = ExprEndResult;
                PG_RETURN_NULL();
        }