From tgl@sss.pgh.pa.us Wed Nov 21 22:51:02 2001 Return-path: 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 ; 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 cc: Peter Eisentraut , PostgreSQL Development , 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 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 Status: ORr Bruce Momjian 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: 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 ; 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 ; 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 cc: Peter Eisentraut , PostgreSQL Development , 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 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 Precedence: bulk Sender: pgsql-bugs-owner@postgresql.org Status: OR Bruce Momjian 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: 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 ; 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 cc: Peter Eisentraut , PostgreSQL Development , 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 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 Status: ORr Bruce Momjian 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: 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 ; 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 ; 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 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 Date: Wed, 21 Nov 2001 23:13:28 -0500 (EST) cc: Peter Eisentraut , PostgreSQL Development , 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: 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 ; 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 X-Sender: To: Tom Lane cc: Bruce Momjian , PostgreSQL Development Subject: Re: [BUGS] Bug #513: union all changes char(3) column definition In-Reply-To: <27975.1006401064@sss.pgh.pa.us> Message-ID: 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()" is even worse because it has no real semantics at all (but you can store bit() in it, interestingly). -- Peter Eisentraut peter_e@gmx.net