pgstat: prepare APIs used by pgstatfuncs for shared memory stats.

With the introduction of PgStat_Kind PgStat_Single_Reset_Type,
PgStat_Shared_Reset_Target don't make sense anymore. Replace them with
PgStat_Kind.

Instead of having dedicated reset functions for different kinds of stats, use
two generic helper routines (one to reset all stats of a kind, one to reset
one stats entry).

A number of reset functions were named pgstat_reset_*_counter(), despite
affecting multiple counters. The generic helper routines get rid of
pgstat_reset_single_counter(), pgstat_reset_subscription_counter().

Rename pgstat_reset_slru_counter(), pgstat_reset_replslot_counter() to
pgstat_reset_slru(), pgstat_reset_replslot() respectively, and have them only
deal with a single SLRU/slot. Resetting all SLRUs/slots goes through the
generic pgstat_reset_of_kind().

Previously pg_stat_reset_replication_slot() used SearchNamedReplicationSlot()
to check if a slot exists. API wise it seems better to move that to
pgstat_replslot.c.

This is done separately from the - quite large - shared memory statistics
patch to make review easier.

Reviewed-By: Kyotaro Horiguchi <[email protected]>
Discussion: https://postgr.es/m/[email protected]

1 files changed, 26 insertions, 11 deletions

diff --git a/src/backend/utils/activity/pgstat_replslot.c b/src/backend/utils/activity/pgstat_replslot.c
index 35078ad73c8..cfaf8d546c5 100644
--- a/src/backend/utils/activity/pgstat_replslot.c
+++ b/src/backend/utils/activity/pgstat_replslot.c
@@ -23,30 +23,45 @@
 
 
 /*
- * Reset counters for a single replication slot, or all replication slots
- * (when name is null).
+ * Reset counters for a single replication slot.
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
 void
-pgstat_reset_replslot_counter(const char *name)
+pgstat_reset_replslot(const char *name)
 {
+	ReplicationSlot *slot;
 	PgStat_MsgResetreplslotcounter msg;
 
+	AssertArg(name != NULL);
+
 	if (pgStatSock == PGINVALID_SOCKET)
 		return;
 
-	if (name)
-	{
-		namestrcpy(&msg.m_slotname, name);
-		msg.clearall = false;
-	}
-	else
-		msg.clearall = true;
+	/*
+	 * Check if the slot exists with the given name. It is possible that by
+	 * the time this message is executed the slot is dropped but at least this
+	 * check will ensure that the given name is for a valid slot.
+	 */
+	slot = SearchNamedReplicationSlot(name, true);
 
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETREPLSLOTCOUNTER);
+	if (!slot)
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("replication slot \"%s\" does not exist",
+						name)));
 
+	/*
+	 * Nothing to do for physical slots as we collect stats only for logical
+	 * slots.
+	 */
+	if (SlotIsPhysical(slot))
+		return;
+
+	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETREPLSLOTCOUNTER);
+	namestrcpy(&msg.m_slotname, name);
+	msg.clearall = false;
 	pgstat_send(&msg, sizeof(msg));
 }