On 3 Feb 2010, at 13:24, Brian Candler wrote:
>> _readers / _admins / _security are stored as a raw object without
>> concurrency control, because keeping them as a document adds too much
>> performance overhead on each request. Concurrency control is a
>> tradeoff we make here.
>
> Sorry to be blunt, but do you have numbers to back that up? This smells
> very much of premature optimisation.
Reading a document costs:
1 disk seek to the end of the db file to grab the b-tree root
+ n disk seeks to the document (n < 5 to 10 in most cases)
In a well cached database, most of the seeks are free, but the last one
usually isn't (unless you can hold a full database in memory).
Doing a disk seek per request is going to kill any sort of performance
we have.
Reading from the process state is effectively free.
This is why stats don't go into a database or my log-to-db branch
is not in trunk.
Cheers
Jan
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