thanks! On Mon, Dec 15, 2008 at 4:16 PM, Igor Tandetnik <[email protected]> wrote: > Sander Jansen <[email protected]> wrote: >> Suppose I have query that does: >> >> SELECT .... FROM table WHERE someinteger IN ( 2,18,19,340,1,72, 15 >> .... ); >> >> The list of numbers comes from a user selection, so it doesn't come >> from some other table. Would it make a big difference in performance >> if I pre-sort this list of numbers or does SQLITE automatically sort >> this (and perhaps maintains an index as well)? > > Looking at EXPLAIN output for such a query, SQLite creates ephemeral > (in-memory) B-tree for the list of integers (essentially, just the index > without the underlying table). So, the numbers will be automatically > arranged into B-tree for fast lookup: their order in the query is > irrelevant (except perhaps for the marginal speed-up in adding them to > the B-tree in the first place, which is probably slightly faster if the > numbers are pre-sorted - but if you don't happen to have them sorted > already, you'll probably spend as much time doing so as SQLite would). > > Igor Tandetnik > > > > _______________________________________________ > sqlite-users mailing list > [email protected] > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users >
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