3 files changed, 56 insertions, 29 deletions

diff --git a/src/backend/utils/activity/pgstat_backend.c b/src/backend/utils/activity/pgstat_backend.c
index 338da73a9a9..3c9ebbcd69c 100644
--- a/src/backend/utils/activity/pgstat_backend.c
+++ b/src/backend/utils/activity/pgstat_backend.c
@@ -26,6 +26,8 @@
 
 #include "access/xlog.h"
 #include "storage/bufmgr.h"
+#include "storage/proc.h"
+#include "storage/procarray.h"
 #include "utils/memutils.h"
 #include "utils/pgstat_internal.h"
 
@@ -83,6 +85,57 @@ pgstat_fetch_stat_backend(ProcNumber procNumber)
 }
 
 /*
+ * Returns statistics of a backend by pid.
+ *
+ * This routine includes sanity checks to ensire that the backend exists and
+ * is running.  "bktype" can be optionally defined to return the BackendType
+ * of the backend whose statistics are returned.
+ */
+PgStat_Backend *
+pgstat_fetch_stat_backend_by_pid(int pid, BackendType *bktype)
+{
+	PGPROC	   *proc;
+	PgBackendStatus *beentry;
+	ProcNumber	procNumber;
+	PgStat_Backend *backend_stats;
+
+	proc = BackendPidGetProc(pid);
+	if (bktype)
+		*bktype = B_INVALID;
+
+	/*
+	 * This could be an auxiliary process but these do not report backend
+	 * statistics due to pgstat_tracks_backend_bktype(), so there is no need
+	 * for an extra call to AuxiliaryPidGetProc().
+	 */
+	if (!proc)
+		return NULL;
+
+	procNumber = GetNumberFromPGProc(proc);
+
+	beentry = pgstat_get_beentry_by_proc_number(procNumber);
+	if (!beentry)
+		return NULL;
+
+	backend_stats = pgstat_fetch_stat_backend(procNumber);
+	if (!backend_stats)
+		return NULL;
+
+	/* if PID does not match, leave */
+	if (beentry->st_procpid != pid)
+		return NULL;
+
+	/* backend may be gone, so recheck in case */
+	if (beentry->st_backendType == B_INVALID)
+		return NULL;
+
+	if (bktype)
+		*bktype = beentry->st_backendType;
+
+	return backend_stats;
+}
+
+/*
  * Flush out locally pending backend IO statistics.  Locking is managed
  * by the caller.
  */
diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index efb6d0032af..68830db8633 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -1576,46 +1576,18 @@ pg_stat_get_backend_io(PG_FUNCTION_ARGS)
 	ReturnSetInfo *rsinfo;
 	BackendType bktype;
 	int			pid;
-	PGPROC	   *proc;
-	ProcNumber	procNumber;
 	PgStat_Backend *backend_stats;
 	PgStat_BktypeIO *bktype_stats;
-	PgBackendStatus *beentry;
 
 	InitMaterializedSRF(fcinfo, 0);
 	rsinfo = (ReturnSetInfo *) fcinfo->resultinfo;
 
 	pid = PG_GETARG_INT32(0);
-	proc = BackendPidGetProc(pid);
-
-	/*
-	 * This could be an auxiliary process but these do not report backend
-	 * statistics due to pgstat_tracks_backend_bktype(), so there is no need
-	 * for an extra call to AuxiliaryPidGetProc().
-	 */
-	if (!proc)
-		return (Datum) 0;
-
-	procNumber = GetNumberFromPGProc(proc);
+	backend_stats = pgstat_fetch_stat_backend_by_pid(pid, &bktype);
 
-	beentry = pgstat_get_beentry_by_proc_number(procNumber);
-	if (!beentry)
-		return (Datum) 0;
-
-	backend_stats = pgstat_fetch_stat_backend(procNumber);
 	if (!backend_stats)
 		return (Datum) 0;
 
-	bktype = beentry->st_backendType;
-
-	/* if PID does not match, leave */
-	if (beentry->st_procpid != pid)
-		return (Datum) 0;
-
-	/* backend may be gone, so recheck in case */
-	if (bktype == B_INVALID)
-		return (Datum) 0;
-
 	bktype_stats = &backend_stats->io_stats;
 
 	/*
diff --git a/src/include/pgstat.h b/src/include/pgstat.h
index 67656264b62..4aad10b0b6d 100644
--- a/src/include/pgstat.h
+++ b/src/include/pgstat.h
@@ -554,6 +554,8 @@ extern void pgstat_count_backend_io_op(IOObject io_object,
 									   IOOp io_op, uint32 cnt,
 									   uint64 bytes);
 extern PgStat_Backend *pgstat_fetch_stat_backend(ProcNumber procNumber);
+extern PgStat_Backend *pgstat_fetch_stat_backend_by_pid(int pid,
+														BackendType *bktype);
 extern bool pgstat_tracks_backend_bktype(BackendType bktype);
 extern void pgstat_create_backend(ProcNumber procnum);