Re: Hot Standby 0.2.1

From: Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com>
To: Simon Riggs <simon(at)2ndQuadrant(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Hot Standby 0.2.1
Date: 2009-09-25 12:50:52
Message-ID: 4ABCBCAC.2010000@enterprisedb.com
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In XidInMVCCSnapshot:
> if (snapshot->takenDuringRecovery)
> {
> /*
> * If the snapshot contains full subxact data, the fastest way to check
> * things is just to compare the given XID against both subxact XIDs and
> * top-level XIDs. If the snapshot overflowed, we have to use pg_subtrans
> * to convert a subxact XID to its parent XID, but then we need only look
> * at top-level XIDs not subxacts.
> */
...
> }
> else
> {
> int32 j;
>
> /*
> *
> * In recovery we store all xids in the subxact array because this
> * is by far the bigger array and we mostly don't know which xids
> * are top-level and which are subxacts. The xip array is empty.
> *
> * We start by searching subtrans, if we overflowed.
> */
...
> }

Hang on, isn't this 180 degrees backwards?

--
Heikki Linnakangas
EnterpriseDB http://www.enterprisedb.com

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