Re: have trouble understanding xmin and xmax with update operations from two different sessions

From: rajan <vgmonnet(at)gmail(dot)com>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: have trouble understanding xmin and xmax with update operations from two different sessions
Date: 2017-07-02 03:55:57
Message-ID: 1498967757297-5969661.post@n3.nabble.com
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Thanks, Jeff. That helps understanding it 50%.

*Session 2* fails to UPDATE the record which is in *(0,2)* and this tuple is
marked for deletion. It means that *(0,2) never exists* when Session 2 is
trying to perform the update.

In that case, how *Session 3's new row (0,4)* contains the xmax as *Session
2's txid*.

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Thanks,
Rajan.
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