[ZODB-Dev] Re: ZODB Benchmarks

[Bernd Dorn]

On 04.03.2008, at 22:16, Shane Hathaway wrote:

> Lennart Regebro wrote:
>> On Tue, Mar 4, 2008 at 9:27 PM, Shane Hathaway  
>> <shane at hathawaymix.org> wrote:
>>> - Did you use optimal methods of retrieval in Postgres?  It is
>>> frequently not necessary to pull the data into the application.   
>>> Copying
>>> to another table could be faster than fetching rows.
>> But is that relevant in this case? Retrieval must reasonably really
>> retrieve the data, not just move it around. :)
>
> Not if you're only retrieving intermediate information.  When you  
> write an application against a relational database, a lot of the  
> intermediate information does not need to be exposed to Python,  
> helping performance significantly.

yes this is the major benefit when using a relational database over  
zodb, because zodb has no server side query language, so the whole  
lookup insert comparison does not reflect real world issues.

for example in one of our applications we have to calculate neighbours  
of users, based on books they have in their bookshelfs. with about  
10000 users and each of them having an average of 100-500 books out of  
ca. 1 million, the calculation of the neighbours takes seconds when  
you have to calculate this on the client, by getting all indexes etc.  
we switched to sql and wrote a single sql statement that does exactly  
the same comparison which now takes about 300ms.

your comparisons would only be accurate if comparing relstorage with  
filestorage over zeo, because in this case there is no server side  
query possible on object attributes . it would be interesting to look  
at performance when having 4-10 zodb clients and then compare zeo/ 
filestorage against relstorage with postgres.



>
>
> Shane
>
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