yoky wrote: > Hi all, > I create a table with 200 columns, then use sqlite3_prepare() and > sqlite3_step()to get a record by this: "select * from tbl where ID =.. ". > Test in my > embedded system,The total time is about 65ms,it is too long for the > performance > requirement, I found sqlite3_prepare() time is about 50ms. > Then test the code with VTune,I found lookupName() function in Sqlite > take about 50% of the total time, and sqlite3StrICmp() occupied most > execution time > (867/922, see the follow pics ) in lookupName(). > The follow is the graph info link generated by VTune: > http://img15.tianya.cn/photo/2008/11/18/10872206_2807293.jpg > http://img15.tianya.cn/photo/2008/11/18/10872205_2807293.jpg > If use "select * from tbl where...." ,tbl is a table with 200 > columns, > sqlite3StrICmp() will be executed more than 20000 times inlookupName(), > this is the main bottleneck in sqlite3_prepare(). > I think maybe Sqlite should do a special optimization for "select * > from tbl .......", > and there is no necessary to compare the column names expanded by "*" with > the table > column names. > Are there some efficient ways to get a whole record with many many > columns ?
the functions you are looking for are sqlite3_reset and sqlite3_bind* Prepare the query just once. Use bound variables to change the id you are looking up. Use _reset to release any locks when not running the query. -- Ian _______________________________________________ sqlite-users mailing list sqlite-users@sqlite.org http://sqlite.org:8080/cgi-bin/mailman/listinfo/sqlite-users
