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@ -100,3 +100,82 @@ Ravensfield Digital Resource Group, Ltd. |
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(740) 587-0114 |
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www.ravensfield.com |
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From reedstrm@rice.edu Wed May 23 10:59:42 2001 |
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Return-path: <reedstrm@rice.edu> |
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Received: from ece.rice.edu (ece.rice.edu [128.42.4.34]) |
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by candle.pha.pa.us (8.10.1/8.10.1) with ESMTP id f4NExgQ05774 |
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id 152a41-0006E5-00 |
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for <pgman@candle.pha.pa.us>; Wed, 23 May 2001 09:56:41 -0500 |
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Date: Wed, 23 May 2001 09:56:41 -0500 |
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From: "Ross J. Reedstrom" <reedstrm@rice.edu> |
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To: Bruce Momjian <pgman@candle.pha.pa.us> |
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Subject: Re: [HACKERS] Re: [GENERAL] Re: [GENERAL] Queries across multiple databases ?(was: SELECT from a table in another database). |
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Message-ID: <20010523095641.D23741@rice.edu> |
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References: <004c01c0e214$ce6c4800$1001a8c0@archonet.com> <200105221131.f4MBVIc28574@candle.pha.pa.us> |
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In-Reply-To: <200105221131.f4MBVIc28574@candle.pha.pa.us>; from pgman@candle.pha.pa.us on Tue, May 22, 2001 at 07:31:18AM -0400 |
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Status: ORr |
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Bruce - |
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Around the first of the year, I started playing around with a schema |
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implementation. As you may recall, my first crack at changing file storage |
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names about a year ago was motivated by the need to avoid collisions |
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once schema were available. |
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Anyway, now that Vadim has removed a lot of the internal dependence |
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on relname for keeping track of relations, using the new relfinenode |
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many places relname used to be used, it seems to me that adding a |
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parallel schemaname to all the data structures that use relname isn't |
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as cumbersome as Peter might think. I hadn't tackled the relcache yet: |
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perhaps concatenating the schemaname and relname to use as the hash key |
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is the way to go for that. |
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Unfortunately, all that code is now 4 months old, and on my machine |
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at home. I has started with the rangetable entries, because hacked the |
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parser to allow 'SELECT * FROM schemaname.tablename' was easier than |
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'select schemaname.tablename.fieldname FROM', since the dot function |
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calling convention isn't allowed in the range list, while it is in the |
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target list. |
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I seem to recall tripping up on the query plan printer, of all things, |
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before other, paying work pushed it aside. I'll see if I can update that |
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code to the current tree, and send you something, if you'd like. |
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Ross |
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On Tue, May 22, 2001 at 07:31:18AM -0400, Bruce Momjian wrote: |
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> > > I'm not sure whether it is quite the way to do it, but I'd have a better |
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> > > time with things if I could span databases in a single request. Are |
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> > > there theoretical problems with spanning databases in a single query? Is |
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> > > it a feature of bad database design & implementation? |
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> > |
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> > I think the developers are planning full schema support for the relatively |
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> > near future (possibly even 7.2, but check the archives and see what's been |
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> > said). Although it looks easy to access a table from another database, |
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> > things can rapidly become more complicated as you start having to deal with |
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> > transactions, triggers, rules, constraints... |
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> |
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> Schema is on my radar screen for 7.2. I am waiting to do some research |
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> in what needs to be done, but my initial idea is to use the system cache |
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> to do namespace mapping, just like is done now for temp tables. |
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> |
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> -- |
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> Bruce Momjian | http://candle.pha.pa.us |
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> pgman@candle.pha.pa.us | (610) 853-3000 |
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> + If your life is a hard drive, | 830 Blythe Avenue |
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> + Christ can be your backup. | Drexel Hill, Pennsylvania 19026 |
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> |
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> ---------------------------(end of broadcast)--------------------------- |
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> TIP 2: you can get off all lists at once with the unregister command |
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> (send "unregister YourEmailAddressHere" to majordomo@postgresql.org) |
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Bruce Momjian
25 years ago