On 10/4/17, sub sk79 <subs...@gmail.com> wrote: > On Wed, Oct 4, 2017 at 12:29 PM, Richard Hipp <d...@sqlite.org> wrote: > >> >> This restriction on the query flattener causes your example >> query above to do what you want. >> > > If subquery-flattening needs to be disabled explicitly, is using "LIMIT -1 > OFFSET 0 " the recommended way? >
Just LIMIT -1 is sufficient. > > >> SQLite version 3.21.0 adds new restrictions on the query flattener >> which allows the application to control whether expensive functions >> (or subqueries) are run before or after sorting. >> > > Is 'expensive' going to be a flag in fourth parameter to create_function > like SQLITE_DETERMINISTIC is? > No. "expensive_function()" is just a place-holder. It might be a large expression, involving one or more subquery expressions, or it might be something that uses a lot of memory rather than a lot of CPU cycles. That is part of the problem of why the query planner has such a hard time determining whether or not to make this optimization automatically - it is difficult to pin down what the application is likely to think is "expensive". -- D. Richard Hipp d...@sqlite.org _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
