At the moment EXPLAIN gives me a very small number of rows for all the queries (thanks to indexes) a part of this one, so if I understand correctly ANALYZE is not needed anymore.
Or I can get a speed up executing once in a while? Regards, Paolo On Sat, May 11, 2013 at 1:06 PM, Clemens Ladisch <clem...@ladisch.de> wrote: > Paolo Bolzoni wrote: >> sqlite> explain query plan SELECT id FROM tour LIMIT 1; >> 0|0|0|SCAN TABLE tour USING COVERING INDEX tour_unsorted_path_idx >> (~1000000 rows) >> >> I am not still sure I understand completely the output of explain >> query plan. > > It means that SQLite estimates that the table (or its index) contains > about 1000000 rows. > > The LIMIT clause is *not* used for this estimate. > >> To get this simple result, sqlite3 actually scans the whole >> table? > > No. Without the LIMIT, the query would scan the entire index. With the > LIMIT, the scan is stopped after the first row. > >> I just have a question about query written in the begin, in my >> application I use it to know if a table is empty. I execute it >> and just use sqlite3_step return value. Errors a part, if it is >> SQLITE_DONE the table is empty, if it is SQLITE_ROW it is not. > > This is more a documentation than an optimization improvement, but if > you are not interested in the value of any particular column, you should > not request it in the first place; i.e., use something like: > SELECT 0 FROM tour LIMIT 1; > > > Regards, > Clemens > _______________________________________________ > sqlite-users mailing list > sqlite-users@sqlite.org > http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
