From: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
---|---|
To: | Kyotaro Horiguchi <horikyota(dot)ntt(at)gmail(dot)com> |
Cc: | jgdr(at)dalibo(dot)com, andres(at)anarazel(dot)de, michael(at)paquier(dot)xyz, sawada(dot)mshk(at)gmail(dot)com, peter(dot)eisentraut(at)2ndquadrant(dot)com, pgsql-hackers(at)lists(dot)postgresql(dot)org, thomas(dot)munro(at)enterprisedb(dot)com, sk(at)zsrv(dot)org, michael(dot)paquier(at)gmail(dot)com |
Subject: | Re: [HACKERS] Restricting maximum keep segments by repslots |
Date: | 2020-03-31 17:18:36 |
Message-ID: | 20200331171836.GA7973@alvherre.pgsql |
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Lists: | pgsql-hackers |
On 2020-Mar-31, Alvaro Herrera wrote:
> I'm not sure if I explained my proposal clearly. What if
> XLogGetLastRemovedSegno returning zero means that every segment is
> valid? We don't need to scan pg_xlog at all.
I mean this:
XLogSegNo
FindOldestXLogFileSegNo(void)
{
XLogSegNo segno = XLogGetLastRemovedSegno();
/* this is the only special case we need to care about */
if (segno == 0)
return some-value;
return segno + 1;
}
... and that point one can further note that a freshly initdb'd system
(no file has been removed) has "1" as the first file. So when segno is
0, you can return 1 and all should be well. That means you can reduce
the function to this:
XLogSegNo
FindOldestXLogFileSegNo(void)
{
return XLogGetLastRemovedSegno() + 1;
}
The tests still pass with this coding.
--
Álvaro Herrera https://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
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