Re: Reviving lost replication slots - Mailing list pgsql-hackers
From | sirisha chamarthi |
---|---|
Subject | Re: Reviving lost replication slots |
Date | |
Msg-id | CAKrAKeXwUOTEVNtw=Jt6ZmFSJsNcFrYvtOhy0oJj_tGefLVB3A@mail.gmail.com Whole thread Raw |
In response to | Re: Reviving lost replication slots (Amit Kapila <amit.kapila16@gmail.com>) |
Responses |
Re: Reviving lost replication slots
|
List | pgsql-hackers |
On Wed, Nov 9, 2022 at 2:37 AM Amit Kapila <amit.kapila16@gmail.com> wrote:
On Fri, Nov 4, 2022 at 1:40 PM sirisha chamarthi
<sirichamarthi22@gmail.com> wrote:
>
Is the intent of setting restart_lsn to InvalidXLogRecPtr was to
disallow reviving the slot?
>
I think the intent is to compute the correct value for
replicationSlotMinLSN as we use restart_lsn for it and using the
invalidated slot's restart_lsn value for it doesn't make sense.
Correct. If a slot is invalidated (lost), then shouldn't we ignore the slot from computing the catalog_xmin? I don't see it being set to InvalidTransactionId in ReplicationSlotsComputeRequiredXmin. Attached a small patch to address this and the output after the patch is as shown below.
postgres=# select * from pg_replication_slots;
slot_name | plugin | slot_type | datoid | database | temporary | active | active_pid | xmin | catalog_xmin | restart_lsn | confirmed_flush_lsn | wal_status | safe_wal_size | two_phase
-----------+---------------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------+------------+---------------+-----------
s2 | test_decoding | logical | 5 | postgres | f | f | | | 771 | 0/30466368 | 0/304663A0 | reserved | 28903824 | f
(1 row)
postgres=# create table t2(c int, c1 char(100));
CREATE TABLE
postgres=# drop table t2;
DROP TABLE
postgres=# vacuum pg_class;
VACUUM
postgres=# select n_dead_tup from pg_stat_all_tables where relname = 'pg_class';
n_dead_tup
------------
2
(1 row)
postgres=# select * from pg_stat_replication;
pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | backend_xmin | state | sent_lsn | write_lsn | flush_lsn | replay_lsn | write_lag | flush_lag | replay_lag | sync_pri
ority | sync_state | reply_time
-----+----------+---------+------------------+-------------+-----------------+-------------+---------------+--------------+-------+----------+-----------+-----------+------------+-----------+-----------+------------+---------
------+------------+------------
(0 rows)
postgres=# insert into t1 select * from t1;
INSERT 0 2097152
postgres=# checkpoint;
CHECKPOINT
postgres=# select * from pg_replication_slots;
slot_name | plugin | slot_type | datoid | database | temporary | active | active_pid | xmin | catalog_xmin | restart_lsn | confirmed_flush_lsn | wal_status | safe_wal_size | two_phase
-----------+---------------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------+------------+---------------+-----------
s2 | test_decoding | logical | 5 | postgres | f | f | | | 771 | | 0/304663A0 | lost | | f
(1 row)
postgres=# vacuum pg_class;
VACUUM
postgres=# select n_dead_tup from pg_stat_all_tables where relname = 'pg_class';
n_dead_tup
------------
0
(1 row)
slot_name | plugin | slot_type | datoid | database | temporary | active | active_pid | xmin | catalog_xmin | restart_lsn | confirmed_flush_lsn | wal_status | safe_wal_size | two_phase
-----------+---------------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------+------------+---------------+-----------
s2 | test_decoding | logical | 5 | postgres | f | f | | | 771 | 0/30466368 | 0/304663A0 | reserved | 28903824 | f
(1 row)
postgres=# create table t2(c int, c1 char(100));
CREATE TABLE
postgres=# drop table t2;
DROP TABLE
postgres=# vacuum pg_class;
VACUUM
postgres=# select n_dead_tup from pg_stat_all_tables where relname = 'pg_class';
n_dead_tup
------------
2
(1 row)
postgres=# select * from pg_stat_replication;
pid | usesysid | usename | application_name | client_addr | client_hostname | client_port | backend_start | backend_xmin | state | sent_lsn | write_lsn | flush_lsn | replay_lsn | write_lag | flush_lag | replay_lag | sync_pri
ority | sync_state | reply_time
-----+----------+---------+------------------+-------------+-----------------+-------------+---------------+--------------+-------+----------+-----------+-----------+------------+-----------+-----------+------------+---------
------+------------+------------
(0 rows)
postgres=# insert into t1 select * from t1;
INSERT 0 2097152
postgres=# checkpoint;
CHECKPOINT
postgres=# select * from pg_replication_slots;
slot_name | plugin | slot_type | datoid | database | temporary | active | active_pid | xmin | catalog_xmin | restart_lsn | confirmed_flush_lsn | wal_status | safe_wal_size | two_phase
-----------+---------------+-----------+--------+----------+-----------+--------+------------+------+--------------+-------------+---------------------+------------+---------------+-----------
s2 | test_decoding | logical | 5 | postgres | f | f | | | 771 | | 0/304663A0 | lost | | f
(1 row)
postgres=# vacuum pg_class;
VACUUM
postgres=# select n_dead_tup from pg_stat_all_tables where relname = 'pg_class';
n_dead_tup
------------
0
(1 row)
--
With Regards,
Amit Kapila.
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