Re: [exim] Tools for SQL export to CDB

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著者: David Saez Padros
日付:  
To: Jeff Garzik
CC: exim users, W B Hacker
題目: Re: [exim] Tools for SQL export to CDB
Hi !!

>> we use here a cdb database for white/black listing that is rebuilt every
>> 5 minutes from a mysql database (with more than 4 million ip addresses),
>> in our case the cdb read speed compensates the databse rebuild every 5
>> minutes. Of course this maybe even better using some dbm like database
>> but we don't have tried it yet. For other purposes where data is updated
>> from time to time is even better (username/passwords, etc ...)
>
> I agree cdb is a nice solution, but I would love to see a comparison
> with SQlite.


the problem with sqlite and also with dbm databases is that writing to
the database locks all database (read/write) and only one process can
update the database (only one write lock) and while the database is
being updated no process can read it, so frequent updates make reading
the database slower. As cdb is read only no locking is required.

> Replacing the cdb database every five minutes seems like it would
> destroy the kernel's ability to cache data.


yes, cdb is better when the database needs little updates, someday i
will try to do the same with dbm but i'm not sure it will be faster.

--
Best regards ...

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