Convert pg_stat_get_backend_idset to use the existing SRF support.

This seems the cleanest way of fixing its lack of a shutdown callback,
which was preventing it from working correctly in a query that didn't
run it to completion.  Per bug report from Szima GÄbor.

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index 03166eac482829ddfbb73e4e1415fbdccc2b75c1..f648b0c1cd2337ef59aa5fb6ab636bf617e1157b 100644 (file)
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1,14 +1,29 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgstatfuncs.c
+ *   Functions for accessing the statistics collector data
+ *
+ * Portions Copyright (c) 1996-2004, PostgreSQL Global Development Group
+ * Portions Copyright (c) 1994, Regents of the University of California
+ *
+ *
+ * IDENTIFICATION
+ *   $PostgreSQL: pgsql/src/backend/utils/adt/pgstatfuncs.c,v 1.19 2004/10/01 21:03:42 tgl Exp $
+ *
+ *-------------------------------------------------------------------------
+ */
 #include "postgres.h"
 
-#include "fmgr.h"
-#include "miscadmin.h"
-#include "utils/hsearch.h"
 #include "access/xact.h"
 #include "catalog/pg_shadow.h"
+#include "fmgr.h"
+#include "funcapi.h"
+#include "miscadmin.h"
 #include "nodes/execnodes.h"
-
 #include "pgstat.h"
+#include "utils/hsearch.h"
 
+/* bogus ... these externs should be in a header file */
 extern Datum pg_stat_get_numscans(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_tuples_returned(PG_FUNCTION_ARGS);
 extern Datum pg_stat_get_tuples_fetched(PG_FUNCTION_ARGS);
@@ -181,40 +196,41 @@ pg_stat_get_blocks_hit(PG_FUNCTION_ARGS)
 Datum
 pg_stat_get_backend_idset(PG_FUNCTION_ARGS)
 {
-   FmgrInfo   *fmgr_info = fcinfo->flinfo;
+   FuncCallContext *funcctx;
+   int        *fctx;
    int32       result;
 
-   if (fcinfo->resultinfo == NULL ||
-       !IsA(fcinfo->resultinfo, ReturnSetInfo))
-       ereport(ERROR,
-               (errcode(ERRCODE_FEATURE_NOT_SUPPORTED),
-                errmsg("set-valued function called in context that "
-                       "cannot accept a set")));
-
-   if (fmgr_info->fn_extra == NULL)
+   /* stuff done only on the first call of the function */
+   if (SRF_IS_FIRSTCALL())
    {
-       if (fmgr_info->fn_mcxt == NULL)
-           elog(ERROR, "no function memory context in set-function");
+       /* create a function context for cross-call persistence */
+       funcctx = SRF_FIRSTCALL_INIT();
 
-       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();
+       fctx = MemoryContextAlloc(funcctx->multi_call_memory_ctx,
+                                 2 * sizeof(int));
+       funcctx->user_fctx = fctx;
+
+       fctx[0] = 0;
+       fctx[1] = pgstat_fetch_stat_numbackends();
    }
 
-   ((int *) (fmgr_info->fn_extra))[0] += 1;
-   result = ((int *) (fmgr_info->fn_extra))[0];
+   /* stuff done on every call of the function */
+   funcctx = SRF_PERCALL_SETUP();
+   fctx = funcctx->user_fctx;
+
+   fctx[0] += 1;
+   result = fctx[0];
 
-   if (result > ((int *) (fmgr_info->fn_extra))[1])
+   if (result <= fctx[1])
    {
-       pfree(fmgr_info->fn_extra);
-       fmgr_info->fn_extra = NULL;
-       ((ReturnSetInfo *) (fcinfo->resultinfo))->isDone = ExprEndResult;
-       PG_RETURN_NULL();
+       /* do when there is more left to send */
+       SRF_RETURN_NEXT(funcctx, Int32GetDatum(result));
+   }
+   else
+   {
+       /* do when there is no more left */
+       SRF_RETURN_DONE(funcctx);
    }
-
-   ((ReturnSetInfo *) (fcinfo->resultinfo))->isDone = ExprMultipleResult;
-   PG_RETURN_INT32(result);
 }