Jens Alfke <j...@mooseyard.com> wrote:
> In a simple SELECT query of a single table, using the C API,
> is there any difference in performance for requesting more or
> fewer columns of the table in the result? Or is the performance
> penalty only incurred when actually reading the column values?
There can sometimes be a big difference.
The less columns you select, the more chance you have
to be able to use a covering index. If the query can use
a covering index, it's likely to have a significant speed up.
According to section 8.0 at https://www.sqlite.org/optoverview.html
being able to use a covering index makes the query about
twice as fast.
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