rdelaage
/
postgresql
mirror of https://git.postgresql.org/git/postgresql.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Add mention of CREATE TABLE and atttypmod problems.

This commit is contained in:
Bruce Momjian 2001-12-05 21:07:23 +00:00
parent 23ea2b12d9
commit 7048c8c6d5
1 changed files with 278 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

278
doc/TODO.detail/atttypmod Normal file
View File

@ -0,0 +1,278 @@
From tgl@sss.pgh.pa.us Wed Nov 21 22:51:02 2001
Return-path: <tgl@sss.pgh.pa.us>
Received: from sss.pgh.pa.us (root@[192.204.191.242])
by candle.pha.pa.us (8.11.6/8.10.1) with ESMTP id fAM3p2v12831
for <pgman@candle.pha.pa.us>; Wed, 21 Nov 2001 22:51:02 -0500 (EST)
Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1])
by sss.pgh.pa.us (8.11.4/8.11.4) with ESMTP id fAM3p4c27978;
Wed, 21 Nov 2001 22:51:04 -0500 (EST)
To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: Peter Eisentraut <peter_e@gmx.net>,
PostgreSQL Development <pgsql-hackers@postgresql.org>,
stiening@cannon.astro.umass.edu, pgsql-bugs@postgresql.org
Subject: Re: [BUGS] Bug #513: union all changes char(3) column definition
In-Reply-To: <200111220310.fAM3A2V08766@candle.pha.pa.us>
References: <200111220310.fAM3A2V08766@candle.pha.pa.us>
Comments: In-reply-to Bruce Momjian <pgman@candle.pha.pa.us>
message dated "Wed, 21 Nov 2001 22:10:02 -0500"
Date: Wed, 21 Nov 2001 22:51:04 -0500
Message-ID: <27975.1006401064@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
Status: ORr
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> Added to TODO:
> * CREATE TABLE AS can not determine column lengths from expressions
> Seems it should be documented. Do we throw an error in these cases?
No. What we do right now is to generate non-length-constrained column
types for the created table.
Your TODO item is too pessimistic: we *do* determine the column length
in simple cases. For example:
regression=# create table foo (f1 char(3));
CREATE
regression=# create table bar as select * from foo;
SELECT
regression=# \d bar
Table "bar"
Column | Type | Modifiers
--------+--------------+-----------
f1 | character(3) |
However, in more complex cases we don't know the column length:
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?
regards, tom lane
From pgsql-bugs-owner+M2695=candle.pha.pa.us=pgman@postgresql.org Wed Nov 21 23:16:19 2001
Return-path: <pgsql-bugs-owner+M2695=candle.pha.pa.us=pgman@postgresql.org>
Received: from rs.postgresql.org (server1.pgsql.org [64.39.15.238] (may be forged))
by candle.pha.pa.us (8.11.6/8.10.1) with ESMTP id fAM4GJv15505
for <pgman@candle.pha.pa.us>; Wed, 21 Nov 2001 23:16:19 -0500 (EST)
Received: from postgresql.org (postgresql.org [64.49.215.8])
by rs.postgresql.org (8.11.6/8.11.6) with ESMTP id fAM4CxN38340
for <pgman@candle.pha.pa.us>; Wed, 21 Nov 2001 22:12:59 -0600 (CST)
(envelope-from pgsql-bugs-owner+M2695=candle.pha.pa.us=pgman@postgresql.org)
Received: from sss.pgh.pa.us ([192.204.191.242])
by postgresql.org (8.11.3/8.11.4) with ESMTP id fAM48em84313;
Wed, 21 Nov 2001 23:08:40 -0500 (EST)
(envelope-from tgl@sss.pgh.pa.us)
Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1])
by sss.pgh.pa.us (8.11.4/8.11.4) with ESMTP id fAM48bc28082;
Wed, 21 Nov 2001 23:08:37 -0500 (EST)
To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: Peter Eisentraut <peter_e@gmx.net>,
PostgreSQL Development <pgsql-hackers@postgresql.org>,
stiening@cannon.astro.umass.edu, pgsql-bugs@postgresql.org
Subject: Re: [BUGS] Bug #513: union all changes char(3) column definition
In-Reply-To: <200111220353.fAM3rRg12994@candle.pha.pa.us>
References: <200111220353.fAM3rRg12994@candle.pha.pa.us>
Comments: In-reply-to Bruce Momjian <pgman@candle.pha.pa.us>
message dated "Wed, 21 Nov 2001 22:53:27 -0500"
Date: Wed, 21 Nov 2001 23:08:37 -0500
Message-ID: <28079.1006402117@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
Precedence: bulk
Sender: pgsql-bugs-owner@postgresql.org
Status: OR
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> However, I don't think creating a bpchar
> with no length is a proper solution. Should we just punt to text in
> these cases?
How many special cases like that do you want to put into the allegedly
datatype-independent CREATE TABLE code?
If I thought this were the only case then I'd not object ... but it
looks like a slippery slope from here.
And --- it's not like replacing "bpchar" with "text" actually buys us
any useful new functionality. AFAICS it's just a cosmetic thing.
regards, tom lane
PS: On the other hand, we might consider attacking the problem from
the reverse direction, ie *removing* code. For example, if there
weren't redundant || operators for char and varchar, then every ||
operation would yield text, and the example we're looking at would
work the way you want for free. I've thought for awhile that we
could use a pass through pg_proc and pg_operator to remove some
entries we don't really need.
---------------------------(end of broadcast)---------------------------
TIP 5: Have you checked our extensive FAQ?
http://www.postgresql.org/users-lounge/docs/faq.html
From tgl@sss.pgh.pa.us Wed Nov 21 23:08:36 2001
Return-path: <tgl@sss.pgh.pa.us>
Received: from sss.pgh.pa.us (root@[192.204.191.242])
by candle.pha.pa.us (8.11.6/8.10.1) with ESMTP id fAM48av14412
for <pgman@candle.pha.pa.us>; Wed, 21 Nov 2001 23:08:36 -0500 (EST)
Received: from sss2.sss.pgh.pa.us (tgl@localhost [127.0.0.1])
by sss.pgh.pa.us (8.11.4/8.11.4) with ESMTP id fAM48bc28082;
Wed, 21 Nov 2001 23:08:37 -0500 (EST)
To: Bruce Momjian <pgman@candle.pha.pa.us>
cc: Peter Eisentraut <peter_e@gmx.net>,
PostgreSQL Development <pgsql-hackers@postgresql.org>,
stiening@cannon.astro.umass.edu, pgsql-bugs@postgresql.org
Subject: Re: [BUGS] Bug #513: union all changes char(3) column definition
In-Reply-To: <200111220353.fAM3rRg12994@candle.pha.pa.us>
References: <200111220353.fAM3rRg12994@candle.pha.pa.us>
Comments: In-reply-to Bruce Momjian <pgman@candle.pha.pa.us>
message dated "Wed, 21 Nov 2001 22:53:27 -0500"
Date: Wed, 21 Nov 2001 23:08:37 -0500
Message-ID: <28079.1006402117@sss.pgh.pa.us>
From: Tom Lane <tgl@sss.pgh.pa.us>
Status: ORr
Bruce Momjian <pgman@candle.pha.pa.us> writes:
> However, I don't think creating a bpchar
> with no length is a proper solution. Should we just punt to text in
> these cases?
How many special cases like that do you want to put into the allegedly
datatype-independent CREATE TABLE code?
If I thought this were the only case then I'd not object ... but it
looks like a slippery slope from here.
And --- it's not like replacing "bpchar" with "text" actually buys us
any useful new functionality. AFAICS it's just a cosmetic thing.
regards, tom lane
PS: On the other hand, we might consider attacking the problem from
the reverse direction, ie *removing* code. For example, if there
weren't redundant || operators for char and varchar, then every ||
operation would yield text, and the example we're looking at would
work the way you want for free. I've thought for awhile that we
could use a pass through pg_proc and pg_operator to remove some
entries we don't really need.
From pgsql-bugs-owner+M2696=candle.pha.pa.us=pgman@postgresql.org Wed Nov 21 23:26:07 2001
Return-path: <pgsql-bugs-owner+M2696=candle.pha.pa.us=pgman@postgresql.org>
Received: from rs.postgresql.org (server1.pgsql.org [64.39.15.238] (may be forged))
by candle.pha.pa.us (8.11.6/8.10.1) with ESMTP id fAM4Q6v16612
for <pgman@candle.pha.pa.us>; Wed, 21 Nov 2001 23:26:06 -0500 (EST)
Received: from postgresql.org (postgresql.org [64.49.215.8])
by rs.postgresql.org (8.11.6/8.11.6) with ESMTP id fAM4MwN38618
for <pgman@candle.pha.pa.us>; Wed, 21 Nov 2001 22:22:58 -0600 (CST)
(envelope-from pgsql-bugs-owner+M2696=candle.pha.pa.us=pgman@postgresql.org)
Received: from candle.pha.pa.us (candle.navpoint.com [162.33.245.46])
by postgresql.org (8.11.3/8.11.4) with ESMTP id fAM4DUm84443;
Wed, 21 Nov 2001 23:13:30 -0500 (EST)
(envelope-from pgman@candle.pha.pa.us)
Received: (from pgman@localhost)
by candle.pha.pa.us (8.11.6/8.10.1) id fAM4DSH15042;
Wed, 21 Nov 2001 23:13:28 -0500 (EST)
From: Bruce Momjian <pgman@candle.pha.pa.us>
Message-ID: <200111220413.fAM4DSH15042@candle.pha.pa.us>
Subject: Re: [BUGS] Bug #513: union all changes char(3) column definition
In-Reply-To: <28079.1006402117@sss.pgh.pa.us> "from Tom Lane at Nov 21, 2001
11:08:37 pm"
To: Tom Lane <tgl@sss.pgh.pa.us>
Date: Wed, 21 Nov 2001 23:13:28 -0500 (EST)
cc: Peter Eisentraut <peter_e@gmx.net>,
PostgreSQL Development <pgsql-hackers@postgresql.org>,
stiening@cannon.astro.umass.edu, pgsql-bugs@postgresql.org
X-Mailer: ELM [version 2.4ME+ PL90 (25)]
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=US-ASCII
Precedence: bulk
Sender: pgsql-bugs-owner@postgresql.org
Status: OR
> How many special cases like that do you want to put into the allegedly
> datatype-independent CREATE TABLE code?
>
> If I thought this were the only case then I'd not object ... but it
> looks like a slippery slope from here.
>
> And --- it's not like replacing "bpchar" with "text" actually buys us
> any useful new functionality. AFAICS it's just a cosmetic thing.
>
> regards, tom lane
>
> PS: On the other hand, we might consider attacking the problem from
> the reverse direction, ie *removing* code. For example, if there
> weren't redundant || operators for char and varchar, then every ||
> operation would yield text, and the example we're looking at would
> work the way you want for free. I've thought for awhile that we
> could use a pass through pg_proc and pg_operator to remove some
> entries we don't really need.
Can we convert bpchar to text in create table if no typmod is supplied?
--
Bruce Momjian | http://candle.pha.pa.us
pgman@candle.pha.pa.us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
---------------------------(end of broadcast)---------------------------
TIP 1: subscribe and unsubscribe commands go to majordomo@postgresql.org
From peter_e@gmx.net Thu Nov 22 12:14:01 2001
Return-path: <peter_e@gmx.net>
Received: from mout02.kundenserver.de (mout02.kundenserver.de [195.20.224.133])
by candle.pha.pa.us (8.11.6/8.10.1) with ESMTP id fAMHE0v13505
for <pgman@candle.pha.pa.us>; Thu, 22 Nov 2001 12:14:00 -0500 (EST)
Received: from [195.20.224.204] (helo=mrvdom00.schlund.de)
by mout02.kundenserver.de with esmtp (Exim 2.12 #2)
id 166xQB-0005p4-00; Thu, 22 Nov 2001 18:13:55 +0100
Received: from p3e9e70dc.dip0.t-ipconnect.de ([62.158.112.220])
by mrvdom00.schlund.de with esmtp (Exim 2.12 #2)
id 166xQ9-00065m-00; Thu, 22 Nov 2001 18:13:53 +0100
Date: Thu, 22 Nov 2001 18:21:17 +0100 (CET)
From: Peter Eisentraut <peter_e@gmx.net>
X-Sender: <peter@peter.localdomain>
To: Tom Lane <tgl@sss.pgh.pa.us>
cc: Bruce Momjian <pgman@candle.pha.pa.us>,
PostgreSQL Development <pgsql-hackers@postgresql.org>
Subject: Re: [BUGS] Bug #513: union all changes char(3) column definition
In-Reply-To: <27975.1006401064@sss.pgh.pa.us>
Message-ID: <Pine.LNX.4.30.0111221803230.766-100000@peter.localdomain>
MIME-Version: 1.0
Content-Type: TEXT/PLAIN; charset=US-ASCII
Status: OR
Tom Lane writes:
> 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 would like to know what Proprietary database #1 does with
CREATE TABLE one ( a bit(6) );
INSERT INTO one VALUES ( b'101101' );
CREATE TABLE two ( b bit(4) );
INSERT INTO two VALUES ( b'0110' );
CREATE TABLE three AS SELECT a FROM one UNION SELECT b FROM two;
According to SQL92, clause 9.3, the result type of the union is bit(6).
However, it's not possible to store a bit(4) value into a bit(6) field.
Our current solution, "bit(<nothing>)" is even worse because it has no
real semantics at all (but you can store bit(<anything>) in it,
interestingly).
--
Peter Eisentraut peter_e@gmx.net