bash wrote:
Why full table scan? :/
SQLite can takes set (1) of rowid by ex(x) index for
"X=5". Then takes another set (2) of rowid by ex(y) for "Y=7".
Then SQLite need only to union this two set (1) and (2).
Final SQLite should returns rows where rowid in (set1 union set2).
I think you mean intersection where you have used union. SQLite won't
optimize the query this way, but you can do it manually.
Instead of
select * from ex4 where x = 5 or y = 7;
You can do this
select * from ex4 where rowid in
(
select rowid from ex4 where x = 5
intersect
select rowid from ex4 where y = 7
);
The intersect operation allows each of the sub-selects to be executed
using an independent index, and the outer select uses the implicit index
on the rowid.
HTH
Dennis Cote
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