[yunqa.de] Re: Subscription confirmation for 'yunqa'
- From: Jacque Lafitte <jacque_lafitte@xxxxxxxxxxx>
- To: <yunqa@xxxxxxxxxxxxx>
- Date: Tue, 27 Nov 2012 08:26:22 +0100
Hello,
I have created a sample database where you can reproduce my performance
problem. The database is however rather large (900 MB). How can I send it to
you?
Best regards,
Jacque
> Date: Mon, 22 Oct 2012 11:20:59 +0200
> From: delphi@xxxxxxxx
> To: yunqa@xxxxxxxxxxxxx
> Subject: [yunqa.de] Re: Subscription confirmation for 'yunqa'
>
> On 20.10.2012 11:37, Jacque Lafitte wrote:
>
> > I have been investigating a bit more and it seems like the performance
> > problem is caused by the presence of two BLOB-fields in the table. When
> > I empty these fields the performance is normal again.
> >
> > To remedy the problem I have tried to change the page size but it seems
> > to have no effect on performance.
> >
> > What is the best way to solve this problem?
>
> I still don't know your database schema so the following suggestions
> might not apply to you.
>
> Background: Access to blob fields via sqlite3_column_blob() reads the
> entire blob contents from the database. This can be slow if the blobs
> are huge.
>
> Suggestion: Rephrase your main query to exclude such blob fields. Then
> run a 2nd query which retrieves only the blob fields and only if you
> really need them.
>
> Using incremental blob I/O for the 2nd query might be even faster. It is
> documented at the sqlite3_blob_open() keyword and demonstrated at the
> DISQLite3_Incremental_Blob example project.
>
> Ralf
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>
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