From: Alvaro Herrera <alvherre@2ndquadrant.com>
To: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
Cc: jgdr@dalibo.com
Cc: andres@anarazel.de
Cc: michael@paquier.xyz
Cc: sawada.mshk@gmail.com
Cc: peter.eisentraut@2ndquadrant.com
Cc: pgsql-hackers@lists.postgresql.org
Cc: thomas.munro@enterprisedb.com
Cc: sk@zsrv.org
Cc: michael.paquier@gmail.com
Subject: Re: [HACKERS] Restricting maximum keep segments by repslots
Date: Tue, 31 Mar 2020 14:18:36 -0300
Message-ID: <20200331171836.GA7973@alvherre.pgsql> (raw)
In-Reply-To: <20200331150755.GA3858@alvherre.pgsql>
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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Cc: alvherre@2ndquadrant.com, horikyota.ntt@gmail.com, jgdr@dalibo.com, andres@anarazel.de, michael@paquier.xyz, sawada.mshk@gmail.com, peter.eisentraut@2ndquadrant.com, pgsql-hackers@lists.postgresql.org, thomas.munro@enterprisedb.com, sk@zsrv.org, michael.paquier@gmail.com
Subject: Re: [HACKERS] Restricting maximum keep segments by repslots
In-Reply-To: <20200331171836.GA7973@alvherre.pgsql>
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