Horton

RE: Slot's restart_lsn may point to removed WAL segment after hard restart unexpectedly

Hayato Kuroda (Fujitsu) <kuroda.hayato@fujitsu.com>

View thread
From: "Hayato Kuroda (Fujitsu)" <kuroda.hayato@fujitsu.com>
To: 'Alexander Korotkov' <aekorotkov@gmail.com>
Cc: Tom Lane <tgl@sss.pgh.pa.us>, Alexander Lakhin <exclusion@gmail.com>, Vitaly Davydov <v.davydov@postgrespro.ru>, Amit Kapila <amit.kapila16@gmail.com>, pgsql-hackers <pgsql-hackers@postgresql.org>, Masahiko Sawada <sawada.mshk@gmail.com>, "tomas@vondra.me" <tomas@vondra.me>
Date: 2025-06-16T11:44:44Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. Update comment for ReplicationSlot.last_saved_restart_lsn

  2. Fix CheckPointReplicationSlots() with max_replication_slots == 0

  3. Remove excess assert from InvalidatePossiblyObsoleteSlot()

  4. Improve runtime and output of tests for replication slots checkpointing.

  5. Keep WAL segments by slot's last saved restart LSN

  6. Fix an assert in CheckPointReplicationSlots().

Dear Alexander,

> Thank you!  All of these totally make sense.  The updated patch is attached.

Thanks for the update. I found another point.

```
-# Another 2M rows; that's about 260MB (~20 segments) worth of WAL.
+# Another 50K rows; that's about 86MB (~5 segments) worth of WAL.
 $node->safe_psql('postgres',
-	q{insert into t (b) select md5(i::text) from generate_series(1,1000000) s(i)}
+	q{insert into t (b) select repeat(md5(i::text),50) from generate_series(1,50000) s(i)}
 );
```

I think a perl function advance_wal() can be used instead of doing actual INSERT
command because no one refers the replicated result. Same thing can be said in
046/047.

Best regards,
Hayato Kuroda
FUJITSU LIMITED