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Re: Wal file query - Mailing list pgsql-general

From Kashif Zeeshan
Subject Re: Wal file query
Date
Msg-id CAAPsdhdgwy4rgSUXAf_b+QVMtFyX2mKbfy6UwP=p824OWeMTBw@mail.gmail.com
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In response to Wal file query  (Atul Kumar <akumar14871@gmail.com>)
Responses Re: Wal file query
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Hi Atul

Start by looking at the current WAL LSN and insert LSN. The pg_current_wal_lsn is the location of the last write. The pg_current_wal_insert_lsn is the logical location and reflects data in the buffer that has not been written to disk. There is also a flush value that shows what has been written to durable storage.
[postgres] # select pg_current_wal_lsn(), pg_current_wal_insert_lsn(); pg_current_wal_lsn | pg_current_wal_insert_lsn
--------------------+--------------------------- 76/7D000000        | 76/7D000028
(1 row)

Although you can guess the name of the WAL file based on the above output, it is best to use the pg_walfile_name function.

[postgres] # select pg_walfile_name('76/7D000028');     pg_walfile_name
-------------------------- 00000001000000760000007D
(1 row)

For details visit following link : https://www.crunchydata.com/blog/postgres-wal-files-and-sequuence-numbers

Thanks
Kashif Zeeshan


On Tue, Apr 8, 2025 at 4:44 PM Atul Kumar <akumar14871@gmail.com> wrote:
In streaming replication What is the way to check which "WAL file" is currently in use in primary  and in standby ?


Regards.

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