Remove excess assert from InvalidatePossiblyObsoleteSlot()

akorotkov · akorotkov · commit 70d8a91f82f1 · 2025-06-23T21:27:42.000+03:00
ca307d5 introduced keeping WAL segments by slot's last saved restart LSN. It also added an assertion that the slot's restart LSN never goes backward. However, situations when the restart LSN goes backward have been spotted by buildfarm animals and investigated in the thread. When pg_receivewal starts the replication, it sets the last replayed LSN to the beginning of the segment, which is older than what ReplicationSlotReserveWal() set for the slot. A similar situation can happen to pg_basebackup. When standby reconnects to the primary, it sends the last replayed LSN, which might be older than the last confirmed flush LSN. In both these situations, a concurrent checkpoint may trigger an assert trap. Based on ideas from Vitaly Davydov <v.davydov@postgrespro.ru>, Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>, Vignesh C <vignesh21@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>. Reported-by: Vignesh C <vignesh21@gmail.com> Reported-by: Tom Lane <tgl@sss.pgh.pa.us> Discussion: https://postgr.es/m/CALDaNm3s-jpQTe1MshsvQ8GO%3DTLj233JCdkQ7uZ6pwqRVpxAdw%40mail.gmail.com Reviewed-by: Vignesh C <vignesh21@gmail.com> Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
diff --git a/src/backend/replication/slot.c b/src/backend/replication/slot.c
@@ -1810,8 +1810,6 @@ InvalidatePossiblyObsoleteSlot(uint32 possible_causes,
 		 */
 		SpinLockAcquire(&s->mutex);
 
-		Assert(s->data.restart_lsn >= s->last_saved_restart_lsn);
-
 		restart_lsn = s->data.restart_lsn;
 
 		/* we do nothing if the slot is already invalid */
