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]

Author: anarazel

src/backend/postmaster/pgstat.c

@@ -124,7 +124,7 @@ static bool pgstat_write_statsfile_needed(void);
 static bool pgstat_db_requested(Oid databaseid);
 
 static PgStat_StatReplSlotEntry *pgstat_get_replslot_entry(NameData name, bool create_it);
-static void pgstat_reset_replslot(PgStat_StatReplSlotEntry *slotstats, TimestampTz ts);
+static void pgstat_reset_replslot_entry(PgStat_StatReplSlotEntry *slotstats, TimestampTz ts);
 
 static HTAB *pgstat_collect_oids(Oid catalogid, AttrNumber anum_oid);
 
@@ -1084,55 +1084,110 @@ pgstat_reset_counters(void)
 }
 
 /*
- * Reset a single counter.
+ * Reset a single variable-numbered entry.
+ *
+ * If the stats kind is within a database, also reset the database's
+ * stat_reset_timestamp.
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
 void
-pgstat_reset_single_counter(Oid objoid, PgStat_Single_Reset_Type type)
+pgstat_reset(PgStat_Kind kind, Oid dboid, Oid objoid)
 {
-	PgStat_MsgResetsinglecounter msg;
 
 	if (pgStatSock == PGINVALID_SOCKET)
 		return;
 
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSINGLECOUNTER);
-	msg.m_databaseid = MyDatabaseId;
-	msg.m_resettype = type;
-	msg.m_objectid = objoid;
+	switch (kind)
+	{
+		case PGSTAT_KIND_FUNCTION:
+		case PGSTAT_KIND_RELATION:
+			{
+				PgStat_MsgResetsinglecounter msg;
 
-	pgstat_send(&msg, sizeof(msg));
+				pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSINGLECOUNTER);
+				msg.m_databaseid = dboid;
+				msg.m_resettype = kind;
+				msg.m_objectid = objoid;
+				pgstat_send(&msg, sizeof(msg));
+			}
+			break;
+
+		case PGSTAT_KIND_SUBSCRIPTION:
+			{
+				PgStat_MsgResetsubcounter msg;
+
+				Assert(dboid == InvalidOid);
+				msg.m_subid = objoid;
+				pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSUBCOUNTER);
+			}
+			break;
+
+		default:
+			elog(ERROR, "unexpected");
+	}
 }
 
 /*
- * Reset cluster-wide shared counters.
+ * Reset stats for all entries of a kind.
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
 void
-pgstat_reset_shared_counters(const char *target)
+pgstat_reset_of_kind(PgStat_Kind kind)
 {
-	PgStat_MsgResetsharedcounter msg;
-
 	if (pgStatSock == PGINVALID_SOCKET)
 		return;
 
-	if (strcmp(target, "archiver") == 0)
-		msg.m_resettarget = RESET_ARCHIVER;
-	else if (strcmp(target, "bgwriter") == 0)
-		msg.m_resettarget = RESET_BGWRITER;
-	else if (strcmp(target, "wal") == 0)
-		msg.m_resettarget = RESET_WAL;
-	else
-		ereport(ERROR,
-				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-				 errmsg("unrecognized reset target: \"%s\"", target),
-				 errhint("Target must be \"archiver\", \"bgwriter\", or \"wal\".")));
+	switch (kind)
+	{
+		case PGSTAT_KIND_ARCHIVER:
+		case PGSTAT_KIND_BGWRITER:
+		case PGSTAT_KIND_CHECKPOINTER:
+		case PGSTAT_KIND_WAL:
+			{
+				PgStat_MsgResetsharedcounter msg;
 
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSHAREDCOUNTER);
-	pgstat_send(&msg, sizeof(msg));
+				pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSHAREDCOUNTER);
+				msg.m_resettarget = kind;
+				pgstat_send(&msg, sizeof(msg));
+			}
+			break;
+		case PGSTAT_KIND_SLRU:
+			{
+				PgStat_MsgResetslrucounter msg;
+
+				pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSLRUCOUNTER);
+				msg.m_index = -1;
+				pgstat_send(&msg, sizeof(msg));
+			}
+			break;
+		case PGSTAT_KIND_REPLSLOT:
+			{
+				PgStat_MsgResetreplslotcounter msg;
+
+				pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETREPLSLOTCOUNTER);
+				msg.clearall = true;
+				pgstat_send(&msg, sizeof(msg));
+			}
+			break;
+
+		case PGSTAT_KIND_SUBSCRIPTION:
+			{
+				PgStat_MsgResetsubcounter msg;
+
+				msg.m_subid = InvalidOid;
+				pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSUBCOUNTER);
+
+				pgstat_send(&msg, sizeof(msg));
+			}
+			break;
+
+		default:
+			elog(ERROR, "unexpected");
+	}
 }
 
 /*
@@ -1954,7 +2009,7 @@ pgstat_get_replslot_entry(NameData name, bool create)
 	if (create && !found)
 	{
 		namestrcpy(&(slotent->slotname), NameStr(name));
-		pgstat_reset_replslot(slotent, 0);
+		pgstat_reset_replslot_entry(slotent, 0);
 	}
 
 	return slotent;
@@ -1964,7 +2019,7 @@ pgstat_get_replslot_entry(NameData name, bool create)
  * Reset the given replication slot stats.
  */
 static void
-pgstat_reset_replslot(PgStat_StatReplSlotEntry *slotent, TimestampTz ts)
+pgstat_reset_replslot_entry(PgStat_StatReplSlotEntry *slotent, TimestampTz ts)
 {
 	/* reset only counters. Don't clear slot name */
 	slotent->spill_txns = 0;
@@ -3528,7 +3583,8 @@ pgstat_recv_resetcounter(PgStat_MsgResetcounter *msg, int len)
 static void
 pgstat_recv_resetsharedcounter(PgStat_MsgResetsharedcounter *msg, int len)
 {
-	if (msg->m_resettarget == RESET_BGWRITER)
+	if (msg->m_resettarget == PGSTAT_KIND_BGWRITER ||
+		msg->m_resettarget == PGSTAT_KIND_CHECKPOINTER)
 	{
 		/*
 		 * Reset the global, bgwriter and checkpointer statistics for the
@@ -3537,13 +3593,13 @@ pgstat_recv_resetsharedcounter(PgStat_MsgResetsharedcounter *msg, int len)
 		memset(&globalStats, 0, sizeof(globalStats));
 		globalStats.bgwriter.stat_reset_timestamp = GetCurrentTimestamp();
 	}
-	else if (msg->m_resettarget == RESET_ARCHIVER)
+	else if (msg->m_resettarget == PGSTAT_KIND_ARCHIVER)
 	{
 		/* Reset the archiver statistics for the cluster. */
 		memset(&archiverStats, 0, sizeof(archiverStats));
 		archiverStats.stat_reset_timestamp = GetCurrentTimestamp();
 	}
-	else if (msg->m_resettarget == RESET_WAL)
+	else if (msg->m_resettarget == PGSTAT_KIND_WAL)
 	{
 		/* Reset the WAL statistics for the cluster. */
 		memset(&walStats, 0, sizeof(walStats));
@@ -3577,10 +3633,10 @@ pgstat_recv_resetsinglecounter(PgStat_MsgResetsinglecounter *msg, int len)
 	dbentry->stat_reset_timestamp = GetCurrentTimestamp();
 
 	/* Remove object if it exists, ignore it if not */
-	if (msg->m_resettype == RESET_TABLE)
+	if (msg->m_resettype == PGSTAT_KIND_RELATION)
 		(void) hash_search(dbentry->tables, (void *) &(msg->m_objectid),
 						   HASH_REMOVE, NULL);
-	else if (msg->m_resettype == RESET_FUNCTION)
+	else if (msg->m_resettype == PGSTAT_KIND_FUNCTION)
 		(void) hash_search(dbentry->functions, (void *) &(msg->m_objectid),
 						   HASH_REMOVE, NULL);
 }
@@ -3626,7 +3682,7 @@ pgstat_recv_resetreplslotcounter(PgStat_MsgResetreplslotcounter *msg,
 
 		hash_seq_init(&sstat, replSlotStatHash);
 		while ((slotent = (PgStat_StatReplSlotEntry *) hash_seq_search(&sstat)) != NULL)
-			pgstat_reset_replslot(slotent, ts);
+			pgstat_reset_replslot_entry(slotent, ts);
 	}
 	else
 	{
@@ -3643,7 +3699,7 @@ pgstat_recv_resetreplslotcounter(PgStat_MsgResetreplslotcounter *msg,
 			return;
 
 		/* Reset the stats for the requested replication slot */
-		pgstat_reset_replslot(slotent, ts);
+		pgstat_reset_replslot_entry(slotent, ts);
 	}
 }
 
@@ -3963,7 +4019,7 @@ pgstat_recv_replslot(PgStat_MsgReplSlot *msg, int len)
 			 * lost, slotent has stats for the old slot. So we initialize all
 			 * counters at slot creation.
 			 */
-			pgstat_reset_replslot(slotent, 0);
+			pgstat_reset_replslot_entry(slotent, 0);
 		}
 		else
 		{

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));
 }
 

src/backend/utils/activity/pgstat_slru.c

@@ -33,21 +33,23 @@ static PgStat_MsgSLRU SLRUStats[SLRU_NUM_ELEMENTS];
 
 
 /*
- * Reset counters for a single SLRU, or all SLRUs (when name is null).
+ * Reset counters for a single SLRU.
  *
  * Permission checking for this function is managed through the normal
  * GRANT system.
  */
 void
-pgstat_reset_slru_counter(const char *name)
+pgstat_reset_slru(const char *name)
 {
 	PgStat_MsgResetslrucounter msg;
 
+	AssertArg(name != NULL);
+
 	if (pgStatSock == PGINVALID_SOCKET)
 		return;
 
 	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSLRUCOUNTER);
-	msg.m_index = (name) ? pgstat_slru_index(name) : -1;
+	msg.m_index = pgstat_slru_index(name);
 
 	pgstat_send(&msg, sizeof(msg));
 }

src/backend/utils/activity/pgstat_subscription.c

@@ -20,27 +20,6 @@
 #include "utils/pgstat_internal.h"
 
 
-/*
- * Reset counters for a single subscription, or all subscriptions (when subid
- * is InvalidOid).
- *
- * Permission checking for this function is managed through the normal
- * GRANT system.
- */
-void
-pgstat_reset_subscription_counter(Oid subid)
-{
-	PgStat_MsgResetsubcounter msg;
-
-	if (pgStatSock == PGINVALID_SOCKET)
-		return;
-
-	msg.m_subid = subid;
-	pgstat_setheader(&msg.m_hdr, PGSTAT_MTYPE_RESETSUBCOUNTER);
-
-	pgstat_send(&msg, sizeof(msg));
-}
-
 /*
  * Report a subscription error.
  */