Message-ID: <43F46C5E.8090806@logix-tt.com>
Date: Thu, 16 Feb 2006 13:13:18 +0100
From: Markus Schaber <schabi@logix-tt.com>
Organization: Logical Tracking and Tracing International AG, Switzerland
User-Agent: Debian Thunderbird 1.0.7 (X11/20051017)
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To: Antal Attila <atesz@ritek.hu>
Cc: pgsql-sql@postgresql.org
Subject: Re: VIEWs and TEMP tables problem
References: <43F4617E.9060708@ritek.hu>
In-Reply-To: <43F4617E.9060708@ritek.hu>
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Hi, Antal,

Antal Attila wrote:

> CREATE VIEW a_view AS SELECT * FROM a JOIN actual_code AC ON (a.code =
> AC.code);

Here, you bind the View to the permanent table.

> CREATE TEMP TABLE actual_code AS SELECT 23::INT4 AS code;

And here you create the temp table that will hide the permanent table.

> I read the temporally table definition in the documentation
> (http://www.postgresql.org/docs/8.1/interactive/sql-createtable.html)
> and I concluded it should be working.

I would not think so, as it states "unless they are referenced with
schema-qualified names". So the permanent table is not removed, only
hidden in the default (non-qualified) name space.

Views don't look up the tables by name. Views bind to the table via
internal ids, and this binding is strong enough to survive even a table
rename, still referencing the same table.

> Is it BUG, or FEATURE? Has anybody got good ideas for solve this problem?

It is a feature.

> This construction came to my mind, because I tried to solve my another
> question:
> http://groups.google.co.hu/group/pgsql.performance/browse_thread/thread/c7aec005f4a1f3eb/83fa0053cad33dea

Maybe you try:
CREATE VIEW ab_view AS
        SELECT a.id AS id,
                       a.userid AS userid,
                       a.col AS col_a, b.col AS col_b
        FROM a LEFT JOIN b ON (a.id = b.a_id AND a.userid=b.userid);

EXPLAIN ANALYSE SELECT * FROM ab_view
        WHERE userid = 23 AND col_a LIKE 's%'
        ORDER BY col_b
        LIMIT 10 OFFSET 10;

HTH,
Markus
-- 
Markus Schaber | Logical Tracking&Tracing International AG
Dipl. Inf.     | Software Development GIS

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