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 <horikyota.ntt@gmail.com>
Discussion: https://postgr.es/m/20220404041516.cctrvpadhuriawlq@alap3.anarazel.de

1 files changed, 32 insertions, 36 deletions

diff --git a/src/backend/utils/adt/pgstatfuncs.c b/src/backend/utils/adt/pgstatfuncs.c
index fd4276fbc67..709dd5548ac 100644
--- a/src/backend/utils/adt/pgstatfuncs.c
+++ b/src/backend/utils/adt/pgstatfuncs.c
@@ -24,7 +24,6 @@
 #include "pgstat.h"
 #include "postmaster/bgworker_internals.h"
 #include "postmaster/postmaster.h"
-#include "replication/slot.h"
 #include "storage/proc.h"
 #include "storage/procarray.h"
 #include "utils/acl.h"
@@ -2075,7 +2074,24 @@ pg_stat_reset_shared(PG_FUNCTION_ARGS)
 {
 	char	   *target = text_to_cstring(PG_GETARG_TEXT_PP(0));
 
-	pgstat_reset_shared_counters(target);
+	if (strcmp(target, "archiver") == 0)
+		pgstat_reset_of_kind(PGSTAT_KIND_ARCHIVER);
+	else if (strcmp(target, "bgwriter") == 0)
+	{
+		/*
+		 * Historically checkpointer was part of bgwriter, continue to reset
+		 * both for now.
+		 */
+		pgstat_reset_of_kind(PGSTAT_KIND_BGWRITER);
+		pgstat_reset_of_kind(PGSTAT_KIND_CHECKPOINTER);
+	}
+	else if (strcmp(target, "wal") == 0)
+		pgstat_reset_of_kind(PGSTAT_KIND_WAL);
+	else
+		ereport(ERROR,
+				(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
+				 errmsg("unrecognized reset target: \"%s\"", target),
+				 errhint("Target must be \"archiver\", \"bgwriter\", or \"wal\".")));
 
 	PG_RETURN_VOID();
 }
@@ -2086,7 +2102,7 @@ pg_stat_reset_single_table_counters(PG_FUNCTION_ARGS)
 {
 	Oid			taboid = PG_GETARG_OID(0);
 
-	pgstat_reset_single_counter(taboid, RESET_TABLE);
+	pgstat_reset(PGSTAT_KIND_RELATION, MyDatabaseId, taboid);
 
 	PG_RETURN_VOID();
 }
@@ -2096,7 +2112,7 @@ pg_stat_reset_single_function_counters(PG_FUNCTION_ARGS)
 {
 	Oid			funcoid = PG_GETARG_OID(0);
 
-	pgstat_reset_single_counter(funcoid, RESET_FUNCTION);
+	pgstat_reset(PGSTAT_KIND_FUNCTION, MyDatabaseId, funcoid);
 
 	PG_RETURN_VOID();
 }
@@ -2107,10 +2123,13 @@ pg_stat_reset_slru(PG_FUNCTION_ARGS)
 {
 	char	   *target = NULL;
 
-	if (!PG_ARGISNULL(0))
+	if (PG_ARGISNULL(0))
+		pgstat_reset_of_kind(PGSTAT_KIND_SLRU);
+	else
+	{
 		target = text_to_cstring(PG_GETARG_TEXT_PP(0));
-
-	pgstat_reset_slru_counter(target);
+		pgstat_reset_slru(target);
+	}
 
 	PG_RETURN_VOID();
 }
@@ -2121,36 +2140,14 @@ pg_stat_reset_replication_slot(PG_FUNCTION_ARGS)
 {
 	char	   *target = NULL;
 
-	if (!PG_ARGISNULL(0))
+	if (PG_ARGISNULL(0))
+		pgstat_reset_of_kind(PGSTAT_KIND_REPLSLOT);
+	else
 	{
-		ReplicationSlot *slot;
-
 		target = text_to_cstring(PG_GETARG_TEXT_PP(0));
-
-		/*
-		 * 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(target, true);
-
-		if (!slot)
-			ereport(ERROR,
-					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-					 errmsg("replication slot \"%s\" does not exist",
-							target)));
-
-		/*
-		 * Nothing to do for physical slots as we collect stats only for
-		 * logical slots.
-		 */
-		if (SlotIsPhysical(slot))
-			PG_RETURN_VOID();
+		pgstat_reset_replslot(target);
 	}
 
-	pgstat_reset_replslot_counter(target);
-
 	PG_RETURN_VOID();
 }
 
@@ -2163,7 +2160,7 @@ pg_stat_reset_subscription_stats(PG_FUNCTION_ARGS)
 	if (PG_ARGISNULL(0))
 	{
 		/* Clear all subscription stats */
-		subid = InvalidOid;
+		pgstat_reset_of_kind(PGSTAT_KIND_SUBSCRIPTION);
 	}
 	else
 	{
@@ -2173,10 +2170,9 @@ pg_stat_reset_subscription_stats(PG_FUNCTION_ARGS)
 			ereport(ERROR,
 					(errcode(ERRCODE_INVALID_PARAMETER_VALUE),
 					 errmsg("invalid subscription OID %u", subid)));
+		pgstat_reset(PGSTAT_KIND_SUBSCRIPTION, InvalidOid, subid);
 	}
 
-	pgstat_reset_subscription_counter(subid);
-
 	PG_RETURN_VOID();
 }