On 11/14/2015 12:33 AM, Johnny Wezel wrote: > I think there is a flaw in information passing between the xBestIndex > and xFilter methods in virtual tables. > > The information about the constraint operation in the aConstraint array > can't reach xFilter. But how is xFilter to know how to set up the cursor > when a statement like > > SELECT * FROM MyTable WHERE a > 10 > > is given? I can pass the index covering a and I can make SQLite pass the > constant 10 to xFilter, but not the > operation. > > IMHO xBestIndex should be called after xOpen as opposed to before and > have a cursor parameter so I can set up the whole filtering information > on my terms. > > Any thoughts on that?
The idea is that your xBestIndex method sets the sqlite3_index_info.idxNum and (optionally) the sqlite3_index_info.idxStr variables, the values of which are then passed to xFilter. So you have to invent some way for xBestIndex to encode the ">" that xFilter understands. https://www.sqlite.org/vtab.html#xbestindex https://www.sqlite.org/vtab.html#xfilter See the rtree module for an example: http://www.sqlite.org/src/artifact/0f9b595bd0deb?ln=1635 I can see your point though. The simple cases would be easier if xFilter were passed something similar to the aConstraint[] array passed to xBestIndex. Dan.
