Re: DROP COLUMN status

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
Cc: Hiroshi Inoue <Inoue(at)tpf(dot)co(dot)jp>, PostgreSQL-development <pgsql-hackers(at)postgreSQL(dot)org>
Subject: Re: DROP COLUMN status
Date: 2000-06-08 19:52:43
Message-ID: 19687.960493963@sss.pgh.pa.us
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>>>> The implementation makes the dropped column invisible by
>>>> changing its attnum to -attnum - offset(currently 20) and
>>>> attnam to ("*already Dropped%d",attnum).
>>
>> Ugh. No wonder you had to hack so many places in such an ugly fashion.
>> Why not leave the attnum as-is, and just add a bool saying "column is
>> dropped" to pg_attribute? As long as the parser ignores columns marked
>> that way for field lookup and expansion of *, it seems the rest of the
>> system wouldn't need to treat dropped columns specially in any way.

> If we leave it as positive, don't we have to change user applications
> that query pg_attribute so they also know to skip it?

Good point, but I think user applications that query pg_attribute
are likely to have trouble anyway: if they're expecting a consecutive
series of attnums then they're going to lose no matter what.

regards, tom lane

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