I'm considering using a virtual table to query an external-to-SQLite data store. However, I've carefully read about the xBestIndex method, and it appears that virtual tables cannot have indexes on expressions; or rather that the SQLite query engine can't make use of such indexes, only indexes on columns.
Consider for example a virtual table with a column named "text", and a query with `WHERE length(text) > 100`. In my external data store I can create an index on `length(text)`, but it doesn't look as though SQLite has any way of asking me about it, so I assume it will just brute-force scan through every row. The only workaround I can see is to add a virtual table column for every possible expression that might be queried against — like "text_length" — but the query interface in my project is open-ended enough that I can't delimit the set of expressions that might need to be exposed this way. (It might be feasible if I could alter the table on the fly to add columns as needed, but the docs explicitly say I can't do that.) —Jens _______________________________________________ sqlite-users mailing list sqlite-users@mailinglists.sqlite.org http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users
