Hi,
I'm just trying to check my understanding of what happens when running a query against SQLite and particularly how that might affect interaction between an application and SQLite. The SQL itself isn't really important for now, but assume it's a select statement which will return some data. From the "3 minute intro" (http://www.sqlite.org/quickstart.html )I understand that the basic steps are: 1) sqlite3_open_v2 - to open my database file for use by SQLite. This returns a database handle. 2) sqlite3_prepare_v2 - this routine results in the sql being "compiled into a byte-code program" (http://www.sqlite.org/c3ref/prepare.html ). This returns a statement handle. 3) sqlite3_step - "this function must be called one or more times to evaluate the statement." (http://www.sqlite.org/c3ref/step.html ) and also return answer rows (the above api may be called multiple times to retrieve all data rows) 4) sqlite3_finalize - to close the statement handle 5) sqlite3_close_v2 - to close the database handle Based on the above and some testing (using 3.20.1): Q1) I believe that the "sqlite3_prepare_v2" function parses the sql text to check it is valid, the named objects exist etc. and builds the 'executable program'. Does this function run the SQL? I don't think so. Q2) At what point in the interaction between an application and the SQLite engine is the sql actually executed? I think this is the first 'sqlite_step' function call. Q3) Are the 'sqlite_prepare' and 'sqlite_step' function calls synchronous? (By which I mean when called, will they wait to finish their processing before returning to the application). Q4) If the function call where the SQLite engine runs the sql is asynchronous then what is the "I'm still running and haven't finished yet" return code? (This question may not be a valid question depending on other answers, but I thought I'd get it out here anyway). Just out of interest: Is the 'executable program' built by 'prepare' the 'virtual machine instructions' as referred to on the EXPLAIN documentation page (http://www.sqlite.org/lang_explain.html )? Cheers, Dave Ward Analytics Ltd - information in motion Tel: +44 (0) 118 9740191 Fax: +44 (0) 118 9740192 www: <http://www.ward-analytics.com> http://www.ward-analytics.com Registered office address: The Oriel, Sydenham Road, Guildford, Surrey, United Kingdom, GU1 3SR Registered company number: 3917021 Registered in England and Wales. _______________________________________________ sqlite-users mailing list [email protected] http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
