0002-Cumulative-statistics-Add-pgstat_drop_entries_of_kin.patch

From d61a9c94325f980c76d548be6db6f6e86f96e0cd Mon Sep 17 00:00:00 2001
From: Lukas Fittl <lukas@fittl.com>
Date: Thu, 2 Jan 2025 10:46:30 -0800
Subject: [PATCH 2/4] Cumulative statistics: Add pgstat_drop_entries_of_kind
 helper

This allows users of the cumulative statistics systems to drop all
entries for a given kind, similar to how pgstat_reset_entries_of_kind
allows resetting all entreis for a given statistics kind.
---
 src/backend/utils/activity/pgstat_shmem.c | 33 +++++++++++++++++++++++
 src/include/utils/pgstat_internal.h       |  1 +
 2 files changed, 34 insertions(+)

diff --git a/src/backend/utils/activity/pgstat_shmem.c b/src/backend/utils/activity/pgstat_shmem.c
index bcc8b2eb4f..43f2dfd695 100644
--- a/src/backend/utils/activity/pgstat_shmem.c
+++ b/src/backend/utils/activity/pgstat_shmem.c
@@ -1015,6 +1015,39 @@ pgstat_drop_all_entries(void)
 		pgstat_request_entry_refs_gc();
 }
 
+void
+pgstat_drop_entries_of_kind(PgStat_Kind kind)
+{
+	dshash_seq_status hstat;
+	PgStatShared_HashEntry *ps;
+	uint64		not_freed_count = 0;
+
+	dshash_seq_init(&hstat, pgStatLocal.shared_hash, true);
+	while ((ps = dshash_seq_next(&hstat)) != NULL)
+	{
+		if (ps->dropped || ps->key.kind != kind)
+			continue;
+
+		/* delete local reference */
+		if (pgStatEntryRefHash)
+		{
+			PgStat_EntryRefHashEntry *lohashent =
+				pgstat_entry_ref_hash_lookup(pgStatEntryRefHash, ps->key);
+
+			if (lohashent)
+				pgstat_release_entry_ref(lohashent->key, lohashent->entry_ref,
+										true);
+		}
+
+		if (!pgstat_drop_entry_internal(ps, &hstat))
+			not_freed_count++;
+	}
+	dshash_seq_term(&hstat);
+
+	if (not_freed_count > 0)
+		pgstat_request_entry_refs_gc();
+}
+
 static void
 shared_stat_reset_contents(PgStat_Kind kind, PgStatShared_Common *header,
 						   TimestampTz ts)
diff --git a/src/include/utils/pgstat_internal.h b/src/include/utils/pgstat_internal.h
index 811ed9b005..900f71c033 100644
--- a/src/include/utils/pgstat_internal.h
+++ b/src/include/utils/pgstat_internal.h
@@ -707,6 +707,7 @@ extern bool pgstat_lock_entry_shared(PgStat_EntryRef *entry_ref, bool nowait);
 extern void pgstat_unlock_entry(PgStat_EntryRef *entry_ref);
 extern bool pgstat_drop_entry(PgStat_Kind kind, Oid dboid, uint64 objid);
 extern void pgstat_drop_all_entries(void);
+extern void pgstat_drop_entries_of_kind(PgStat_Kind kind);
 extern PgStat_EntryRef *pgstat_get_entry_ref_locked(PgStat_Kind kind, Oid dboid, uint64 objid,
 													bool nowait);
 extern void pgstat_reset_entry(PgStat_Kind kind, Oid dboid, uint64 objid, TimestampTz ts);
-- 
2.47.1