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Re: Bug #513: union all changes char(3) column definition

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Peter Eisentraut <peter_e(at)gmx(dot)net>, PostgreSQL Development <pgsql-hackers(at)postgresql(dot)org>, stiening(at)cannon(dot)astro(dot)umass(dot)edu, pgsql-bugs(at)postgresql(dot)org
Subject: Re: Bug #513: union all changes char(3) column definition
Date: 2001-11-22 03:53:27
Message-ID: 200111220353.fAM3rRg12994@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugspgsql-hackers
> regression=# create table baz as select f1 || 'z' as f1 from foo;
> SELECT
> regression=# \d baz
>          Table "baz"
>  Column |  Type  | Modifiers
> --------+--------+-----------
>  f1     | bpchar |
> 
> The argument here is about how much intelligence it's reasonable to
> expect the system to have.  It's very clearly not feasible to derive
> a length limit automagically in every case.  How hard should we try?

I don't think we can try in this case, especially because our functions
are all burried down in adt/.  However, I don't think creating a bpchar
with no length is a proper solution.  Should we just punt to text in
these cases?  Seems cleaner, perhaps even throw an elog(NOTICE)
mentioning the promotion to text.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 853-3000
  +  If your life is a hard drive,     |  830 Blythe Avenue
  +  Christ can be your backup.        |  Drexel Hill, Pennsylvania 19026

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