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Re: [WebSQLDatabase] Adding a vacuum() call

From: João Eiras <joaoe@opera.com>
Date: Mon, 08 Mar 2010 12:39:58 +0100
To: public-webapps <public-webapps@w3.org>
Message-ID: <op.u88yow1i2q99of@id-c0981>

>> I don't see how the callbacks are useful though. Vacuum works
>> transparently, its effects are not visible, and what should the page do  
>> in
>> case of error ?
> i was thinking of something like:
> db.defragment(errorCallback, successCallback);
> showAPrettyImageAndAskTheUserToWait();
> function errorCallback(error) {}
> function successCallback() {
>   getRidOfThePrettyImageAndRestartTheApp();
> }
> just like you, i'm not sure if the error callback is useful at all, but i
> thought i'd add it to make the defragment() call look more like a
> transaction. maybe we don't need it.

True, but this is a kind of operation that could very well just run on the  
background, with a single optional callback when it's done (the webpage  
can't do anything if an error is detected anyway). The user agent would  
need to queue any subsequent transactions if a vacuum is running. I would  
consider it as an hint, and after all webpages that own references to the  
underlying data files are closed, would do a vacuum. So, if you have many  
tabs on gmail, and that a single gmail instance tries to do multiple  
vacuums, it would equiv to one single vacuum operation.

>> Sqlite supports incremental vacuum http://www.sqlite.org/pragma.html so
>> this kind of feature should be left for sqlite to handle for itself.
> in addition to what jeremy said, having auto-vacuum on is going to add  
> some
> performance overhead to every transaction. this is not acceptable to some
> apps.

I perused through the docs, and unfortunately auto-vaccum seems not like  
the ideal solution.


João Eiras
Core Developer, Opera Software ASA, http://www.opera.com/
Received on Monday, 8 March 2010 11:40:37 UTC

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