[Digikam-devel] [Bug 155097] performance problems with recursive view and filtering

Marcel Wiesweg marcel.wiesweg at gmx.de
Thu Sep 4 13:51:15 BST 2008


(sorry for posting with mail, but bko doesnt work at the moment)

I assume you are working on 0.9, but some thoughts on 0.10:
For 0.10, some caching of simple values takes place, so database queries 
should be reduced in some cases. This means, if you are working on 0.10, then 
there is a bug elsewhere.
Caching is easy for rating, date, format, size.
Tags are not cached by default for every image, but only on first demand, so 
minor problem.
The one filter that cannot properly be solved with caching is text. Here it 
would be most interesting to have a SQL solution, like one-big-query. You 
cannot pass say 20000 image ids in one SQL statement. What we can do is use 
prepared queries (this is all 0.10 only), so that the SQL is parsed and only 
the bound values are changed in each run. This is potentially much faster, 
but I have no benchmarks for SQLite. The other solution, building on top of 
the query that was used for the items in the unfiltered view, is easy for 
tags and albums, but difficult for search, from an implementation point of 
view.



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