Re: [HACKERS] Re: ALTER TABLE DROP COLUMN

From: wieck(at)debis(dot)com (Jan Wieck)
To: Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>
Cc: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, PostgreSQL Development <pgsql-hackers(at)postgreSQL(dot)org>, Peter Eisentraut <peter_e(at)gmx(dot)net>
Subject: Re: [HACKERS] Re: ALTER TABLE DROP COLUMN
Date: 2000-02-28 07:56:22
Message-ID: m12PL2U-0003kGC@orion.SAPserv.Hamburg.dsh.de
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Hiroshi Inoue wrote:

> > > Wow, that almost seems to easy to be true. I never thought that having
> > > tuples of different structures in the table at the same time would be
> > > possible. If so then I don't see a reason why this would be too hard to
> > > do.
> >
> > If the transaction is not committed, I don't think anything actually
> > reads the tuple columns, so you are safe.
> >
>
> Hmm,tuples of multiple version in a table ?
> This is neither clean nor easy for me.
> There's no such stuff which takes the case into account,AFAIK.
>
> Seems no one but me object to it. I'm tired of this issue and it's
> painful for me to continue discussion further in my poor English.
> I may be able to provide another implementation on trial and it
> may be easier than only objecting to your proposal.
> Is it OK ?

Consider me on your side.

For some good reasons, I added a

ReferentialIntegritySnapshotOverride

mode, that causes any tuple to be visible when fetched by
CTID. Actually, there will be at least a read lock on them,
so locking will prevent damage. But I can think of other
situations where this kind of "read whatever I want you to"
could be needed and would fail then.

Jan

--

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# It's easier to get forgiveness for being wrong than for being right. #
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#========================================= wieck(at)debis(dot)com (Jan Wieck) #

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