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Re: Unneccessary cmax in heap tuple ?

From: Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>
To: devik(at)cdi(dot)cz
Cc: pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Unneccessary cmax in heap tuple ?
Date: 2000-10-25 09:49:05
Message-ID: 39F6AC91.3F78BDAA@tpf.co.jp (view raw or flat)
Thread:
Lists: pgsql-hackers

devik(at)cdi(dot)cz wrote:

> Hello,
> Why is there cmax in tuple ? cxxx is used to determine
> if tuple was inserted/deleted by current command or
> past command. Because one command can't both insert
> and delete the same tuple, only something like "cupd"
> might be needed and flag which tells you whether cupd
> is time of insert or delete. This saves 4byte from
> header ..
>

If a tuple was inserted and updated in current transaction,
how could we judge if the tuple was valid for a given
ScanCommandId  ?
However there could be other improvements.

Regards.
Hiroshi Inoue


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