Sunday, April 30, 2006

On Performance

Vlad commented:

You mentioned that performance could be improved with this approach, but I'm not
sure how - since this approach involves asking the database for all the records
and then filtering them usig the specs. Using toplink expressions, one can take
advantage of indexes on the database tables and the syntax is quite similar to
specs, so one gets the same kinds of benefits in terms of code duplication. I'd
love to see a posting about performance tuning these spec objects.

Performance for us was not over the database, but the number of times we were looping over the MeasurementPointCollection. Many of our common calls would loop over the measurement point collections two to three times. We saw about a 5% speed up in the tests using the Specification. Not a lot, but something.

Earlier in the project we used Home (Repository Pattern) calls to load the measurement points from the database. We found loading them once and reusing them much faster than using the database. (I think we halved the time the tests took). This is fairly common. (See Fowler PoEAA p.40, Toplink performance In particular, read the question: What are the most common performance related mistakes that you have seen projects make when developing TopLink applications?)


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