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* wal_compression
@ 2025-01-20 10:22 Fabrice Chapuis <[email protected]>
0 siblings, 1 reply; 2+ messages in thread
From: Fabrice Chapuis @ 2025-01-20 10:22 UTC (permalink / raw)
To: [email protected]
In Postgres 17 doc, for wal_compression parameter it's written:
"Turning this parameter on can reduce the WAL volume without increasing the
risk of unrecoverable data corruption"
If wal_compression = on then when a full page is written in the wal, it
will be compressed. What I do not understand is that the wal file keeps the
same size 16Mb. What is the interest to activate wal_compression?
Thanks in advance for explanation
Fabrice
^ permalink raw reply [nested|flat] 2+ messages in thread
* Re: wal_compression
@ 2025-01-20 10:31 Guillaume Lelarge <[email protected]>
parent: Fabrice Chapuis <[email protected]>
0 siblings, 0 replies; 2+ messages in thread
From: Guillaume Lelarge @ 2025-01-20 10:31 UTC (permalink / raw)
To: Fabrice Chapuis <[email protected]>; +Cc: [email protected]
Hi,
Le lun. 20 janv. 2025 à 11:23, Fabrice Chapuis <[email protected]> a
écrit :
> In Postgres 17 doc, for wal_compression parameter it's written:
> "Turning this parameter on can reduce the WAL volume without increasing
> the risk of unrecoverable data corruption"
> If wal_compression = on then when a full page is written in the wal, it
> will be compressed. What I do not understand is that the wal file keeps the
> same size 16Mb. What is the interest to activate wal_compression?
>
>
A WAL file contains some records. Usually a lot of records. If a record is
compressed, it will take less space in the WAL file. Hence, this WAL file
will contain more records, and you will need less WAL files for the same
activity.
--
Guillaume.
^ permalink raw reply [nested|flat] 2+ messages in thread
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