On Tue, 13 Jun 2017 11:53:05 +0200 rv.gauth...@free.fr wrote: > Hi all, > > we are using sqlite3 on an embedded application. > The database is opened in read only mode and can't be modified by the > application. > > I noticed that the first SELECT statement after a BEGIN TRANSACTION > takes at least 14 ms. > All subsequent queries in the same transaction are taking near 0 ms.
The first SELECT says to sqlite to do all the work needed to make your query ACID constraint (acquires locks, malloc ram, generate structs, open files, etc...) > > If I omit the BEGIN TRANSACTION, all queries are taking at least 14 > ms. Because each query automatically is wrapped with BEGIN TRANSACTION / query / END TRANSACTION and the work to make your query ACID is done on every query, not on the first one. > I tried also to do a unique BEGIN TRANSACTION after opening the > database. This fixes the timing issue, but my memory increases > constantly. ... Do you know what's a transaction? In your case it's a read only db and don't think the could be a problem, but in normal use cases could be catastrophic. > Is there a way (pragma, compile flags, ...) to gain these 14 ms for > the first query ? Try openinig with URI, check for 'inmutable' parameter https://www.sqlite.org/draft/c3ref/open.html , perhaps you can gain some ms, but it's dangerous, I warn you. > > Thanks. > > > Hervé Gauthier. > > > _______________________________________________ > sqlite-users mailing list > sqlite-users@mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users --- --- Eduardo Morras <emorr...@yahoo.es> _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
