From: | Vadim Mikheev <vadim(at)krs(dot)ru> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | pgsql-hackers(at)postgreSQL(dot)org |
Subject: | Re: [HACKERS] Bogus "Non-functional update" notices |
Date: | 1998-07-29 01:16:05 |
Message-ID: | 35BE77D5.3023F8B1@krs.ru |
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Lists: | pgsql-hackers |
Tom Lane wrote:
>
> Vadim Mikheev <vadim(at)krs(dot)ru> writes:
> > In UPDATE backend inserts index tuple for new version of heap tuple
> > and adjusts all index scans affected by this insertion.
> > Something is wrong in nbtscan.c:_bt_adjscans()...
>
> Could be; maybe there's one boundary case that fails to advance the
> index scan? I hope there's someone who's looked at nbtree recently
> who can take the time to debug this.
I'll try to look there...
> Another thing that struck me while looking at the update code is that
> an update deletes the old tuple value, then inserts the new value,
> but it doesn't bother to delete any old index entries pointing at the
> old tuple. ISTM that after a while, there are going to be a lot of old
> index entries pointing at dead tuples ... or, perhaps, at *some other*
> live tuple, if the space the dead tuple occupied has been reused for
> something else. This certainly seems to present a risk of returning
> the wrong tuple. I looked through the code to find out how such an
> error is prevented, and didn't find anything. But maybe I just don't
> know where to look.
Vacuum deletes index tuples before deleting heap ones...
Vadim
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