From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
Cc: | Hannu Krosing <hannu(at)tm(dot)ee>, Andreas Pflug <pgadmin(at)pse-consulting(dot)de>, pg(at)fastcrypt(dot)com, Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>, Neil Conway <neilc(at)samurai(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: ALTER COLUMN/logical column position |
Date: | 2003-11-20 15:49:26 |
Message-ID: | 4437.1069343366@sss.pgh.pa.us |
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Lists: | pgsql-hackers |
Peter Eisentraut <peter_e(at)gmx(dot)net> writes:
> Tom Lane writes:
>> Exactly. I'm considerably more worried about breaking out-of-the-way
>> places in the backend than I am about what order someone's admin tool
>> presents the columns in.
> Clearly, the effort of adding logical column numbers will consist of
> making choices between physical and logical numbers in the backend in some
> places. So one option is to replace some uses of attnum by attlognum.
> The other optionis to replace *all* uses of attnum by attphysnum and then
> replace some uses of attphysnum by attnum. To me, this looks like an
> equal "risk" as far as the backend goes.
This would be a reasonable assessment if we had our hands on every line
of backend code that exists. But you are neglecting the probability of
breaking user-written C functions, PL languages outside the main distro,
etc.
If we were going to go about this in a way that does not localize the
changes, I'd be inclined to use "attlognum" and "attphysnum" ... that
is, *deliberately* break every use that hasn't been looked at and
updated. Even that would not guarantee catching all the trouble spots;
for example loop indexes and attnums passed as function parameters might
not have names that would be caught by a simplistic search-and-replace
update.
I'm for localizing the changes.
regards, tom lane
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