On 2/21/16, Olivier Mascia <om at integral.be> wrote: > > The way I had read that documentation is: if your function is meant to be > deterministic, returning the same result for the very same input, at least > for the duration of the SQL statement (or of course always), then you should > tag it as SQLITE_DETERMINISTIC because it is very valuable for the query > planner, in order to optimize its calls while compiling a statement. > > I am not sure at all, reading the doc, that the query planner brings the > guarantee that it will make it so there is a singleton call to the function > (for a given input value) during a statement execution.
Your reading is correct, Olivier. The SQLITE_DETERMINISTIC flag is a promise that the implementation makes to SQLite, which allows the query planner a little more freedom to optimize calls to the function - for example the freedom to call it once during statement initialization and reuse the result multiple times, rather than calling the function multiple times. -- D. Richard Hipp drh at sqlite.org
