| From: | Peter Eisentraut <peter(dot)eisentraut(at)2ndquadrant(dot)com> |
|---|---|
| To: | Luca Ferrari <fluca1978(at)gmail(dot)com>, pgsql-general <pgsql-general(at)postgresql(dot)org> |
| Subject: | Re: question about zeroes in the wal file names |
| Date: | 2019-08-19 07:30:06 |
| Message-ID: | 575bbf91-8666-f573-1d8b-6bfda5e39195@2ndquadrant.com |
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| Lists: | pgsql-general |
On 2019-08-18 16:17, Luca Ferrari wrote:
> I'm just curious to better understand the naming convention behind wal
> files, because I've seen on a system of mine that the wals created
> were:
>
> 000000050000020E000000FF
> 000000050000020F00000000
>
> while I was expecting 20E0x100.
You are in principle correct. This naming system is a historical
accident. The actual LSN associated with the first file is
0000020EFF000000
and so the next one is naturally
0000020F00000000
The reason the zeroes are in there comes from a time when PostgreSQL
didn't fully support 64-bit integers, and the LSNs and the files were
tracked internally as pairs of 32-bit integers.
--
Peter Eisentraut http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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