>FWIW, I've often wondered about the cost estimates of real tables versus >virtual tables, especially since many vtables implementations don't involve >real IO but pure in-memory computations. There's >very little advice or >documentation on this important subject, and Max's email reveals that >empirical testing leading to ad-hoc heuristics are vulnerable to breaking when >SQLite itself evolves. More >guidance and perhaps even some "normative" >documentation is needed IMHO. Thanks, --DD >_______________________________________________
The "estimated cost" is described as "how many disk IO operations are expected". Version higher than 3.8.2 allow setting an "estimatedRows" (default: 25) and versions above 3.9.0 allow setting a flag that indicates that 0 or 1 rows will be returned (i.e. the constraints form a "unique index"). ___________________________________________ Gunter Hick Software Engineer Scientific Games International GmbH FN 157284 a, HG Wien Klitschgasse 2-4, A-1130 Vienna, Austria Tel: +43 1 80100 0 E-Mail: h...@scigames.at This communication (including any attachments) is intended for the use of the intended recipient(s) only and may contain information that is confidential, privileged or legally protected. Any unauthorized use or dissemination of this communication is strictly prohibited. If you have received this communication in error, please immediately notify the sender by return e-mail message and delete all copies of the original communication. Thank you for your cooperation. _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
