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From Charles Anthony <charles.anth...@hpdsoftware.com>
Subject RE: Extent Aware Path Expressions : An Innefficiency ?
Date Tue, 25 Feb 2003 08:33:40 GMT
Hi Jakob,

You're a star. The fix took a query time down from 1500 ms to 40ms (on Ms
SQL Server)

Cheers,
Charles.

>-----Original Message-----
>From: Jakob Braeuchi [mailto:jbraeuchi@gmx.ch]
>Sent: 24 February 2003 19:05
>To: OJB Developers List
>Subject: Re: Extent Aware Path Expressions : An Innefficiency ?
>
>
>hi charles,
>
>i just commited a fix preventing multiple aliases for the same table. 
>please check it out.
>
>hth
>jakob
>
>Charles Anthony wrote:
>
>>Hi All,
>>
>>Back in January, Jakob did a much needed fix for extent aware path
>>expressions :
>>
>>  
>>
>>>Date: Sun, 19 Jan 2003 12:59:28 +0100
>>>From: Jakob Braeuchi <jbraeuchi@gmx.ch>
>>>Subject: extent aware pathExpressions fixed
>>>
>>>hi all,
>>>ojb now provides better support for extent aware path 
>expression. only 
>>>one sql is executed.
>>>the sql containins one 'outer join' for each extent and one 'or' for 
>>>each criteria:
>>>    
>>>
>>
>>  
>>
>>>SELECT DISTINCT A0.KategorieName,A0.Kategorie_Nr,A0.Beschreibung FROM
>>>Kategorien A0
>>>LEFT OUTER JOIN Artikel A1 ON A0.Kategorie_Nr=A1.Kategorie_Nr
>>>LEFT OUTER JOIN BOOKS A1E0 ON A0.Kategorie_Nr=A1E0.Kategorie_Nr
>>>LEFT OUTER JOIN CDS A1E1 ON A0.Kategorie_Nr=A1E1.Kategorie_Nr
>>>WHERE
>>>A1.Artikelname LIKE  'F%'  OR
>>>A1E0.Artikelname LIKE  'F%'  OR
>>>A1E1.Artikelname LIKE  'F%'
>>>    
>>>
>>
>>We are trying to use a path expression on a class which has 
>many (well, 12)
>>extents. All the extents are mapped to the same table.  This 
>yields a sql
>>statment something like 
>>
>>SELECT DISTINCT A0.KategorieName,A0.Kategorie_Nr,A0.Beschreibung FROM
>>Kategorien A0
>>LEFT OUTER JOIN Artikel A1 ON A0.Kategorie_Nr=A1.Kategorie_Nr
>>LEFT OUTER JOIN Artikel A1E0 ON A0.Kategorie_Nr=A1E0.Kategorie_Nr
>>LEFT OUTER JOIN Artikel A1E1 ON A0.Kategorie_Nr=A1E1.Kategorie_Nr
>>LEFT OUTER JOIN Artikel A1E2 ON A0.Kategorie_Nr=A1E1.Kategorie_Nr
>>LEFT OUTER JOIN Artikel A1E3 ON A0.Kategorie_Nr=A1E1.Kategorie_Nr
>>LEFT OUTER JOIN Artikel A1E4 ON A0.Kategorie_Nr=A1E1.Kategorie_Nr
>>LEFT OUTER JOIN Artikel A1E5 ON A0.Kategorie_Nr=A1E1.Kategorie_Nr
>>[...]
>>LEFT OUTER JOIN Artikel A1E11 ON A0.Kategorie_Nr=A1E1.Kategorie_Nr
>>WHERE
>>A1.Artikelname LIKE  'F%'  OR
>>A1E0.Artikelname LIKE  'F%'  OR
>>A1E1.Artikelname LIKE  'F%'  OR
>>A1E2.Artikelname LIKE  'F%'  OR
>>A1E3.Artikelname LIKE  'F%'  OR
>>[...]
>>A1E11.Artikelname LIKE  'F%'  OR
>>
>>This strikes me as likely to be pretty inneficient; as far as 
>I can see,
>>only one join per table should be needed. Am I wrong, and is this easy
>>enough to ?
>>
>>Cheers,
>>
>>Charles.
>>
>>
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