Have you proven that the cpu is the bottleneck? Sorting a million rows seems like a lot, but even older single core cpus may be capable of 2 billion ops per second. [I apologize if this has been sorted out already.... I've got about 2 days of history on the thread]
regards, Adam DeVita On Fri, Sep 16, 2016 at 7:56 AM, Stephen Chrzanowski <pontia...@gmail.com> wrote: > Although programmatically easily done, from the SQLite point of view, what > if that query, sans LIMIT, were a subquery, and the limit was put out on > the outside? Would the inner query execute, use all the threads, then > return just one row on the outer? > > On Fri, Sep 16, 2016 at 7:29 AM, Richard Hipp <d...@sqlite.org> wrote: > > > On 8/14/16, Венцислав Русев <ven...@proxima-3.com> wrote: > > > My computer has 4 cores. I have compile sqlite like this "gcc > > > -DSQLITE_MAX_WORKER_THREADS=4 -DSQLITE_DEFAULT_WORKER_THREADS=4 > shell.c > > > sqlite3.c -lpthread -ldl -o sqlite3". I made some tests and found that > > > "pragma threads = 4" doesn't decrease runtime of the query that sorts 1 > > > milion records. > > > > > > SQLite version 3.8.8 > > > sqlite> pragma threads; > > > 4 > > > sqlite> CREATE TABLE event ( > > > ID INTEGER PRIMARY KEY NOT NULL, > > > date INTEGER NOT NULL, > > > value INTEGER NOT NULL ); > > > sqlite> EXPLAIN QUERY PLAN SELECT ID FROM event ORDER BY date LIMIT 1; > > > > The algorithm used for "ORDER BY ... LIMIT N" uses much less memory > > than a full-up "ORDER BY" because is only keeps track of the top N > > entries seen so far, discarding the rest. But it also only uses a > > single thread. If you want multiple threads to be used, you'll need > > to drop the LIMIT, though I imagine that would defeat your purpose, > > no? > > > > -- > > D. Richard Hipp > > d...@sqlite.org > > _______________________________________________ > > sqlite-users mailing list > > sqlite-users@mailinglists.sqlite.org > > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > > > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users > -- -------------- VerifEye Technologies Inc. 151 Whitehall Dr. Unit 2 Markham, ON L3R 9T1 _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
