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Re: column ordering, was Re: [PATCHES] Enums patch v2

From: "Zeugswetter Andreas ADI SD" <ZeugswetterA(at)spardat(dot)at>
To: "Martijn van Oosterhout" <kleptog(at)svana(dot)org>
Cc: "Andrew Dunstan" <andrew(at)dunslane(dot)net>,"Tom Lane" <tgl(at)sss(dot)pgh(dot)pa(dot)us>,"Robert Treat" <xzilla(at)users(dot)sourceforge(dot)net>,<pgsql-hackers(at)postgresql(dot)org>,"Gregory Stark" <stark(at)enterprisedb(dot)com>
Subject: Re: column ordering, was Re: [PATCHES] Enums patch v2
Date: 2006-12-21 16:18:02
Message-ID: E1539E0ED7043848906A8FF995BDA57901A34ECD@m0143.s-mxs.net (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-patches
> > > The thing is, physical index numbers has meaning, the logical
index
> > > number does not. In a view definition we're going to store the
> > > physical index, not the logical one, for example. We don't want
> > > rearranging columns to invalidate view definitions or plans.
> > 
> > I think we lack a definition here:
> > 
> > logical number:	the order of columns when doing select *
> > physical number:	the position inside the heap tuple (maybe with
> > offset)
> > 
> > All views and plans and index definitions and most everyting else 
> > needs to reference the logical number.
> 
> Huh? If I have an index on the first two columns of a table, 
> it's going
> to refernce columns 1 and 2.
> 
> If you alter the table to put a column in front of those two, the new
> column will be physical 3, logical 1.

No, you change pg_index to now contain 2,3.

> If the index references logical numbers, the index has just been
> broken. If the index references physical numbers, everything works
> without changes.

yup, sinval

> Same with views, if you use logical numbers you have to rebuild the
> view each time. Why bother, when physical numbers work and don't have
> that problem?

Because it would imho be a nightmare to handle ...

Andreas

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