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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Thread: | |
Lists: | pgsql-hackers |
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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