Clemens Ladisch wrote
> For count(*), the database does not need the actual table rows.

I think this is not true, he has a point here: SELECT COUNT(*) WHERE
<idx_key>=? needs to examine every index key prefix (excluding at least
ROWID) that matches. This may mean reading in the whole index.

I think b-trees can store the counts of descendant nodes for every node to
solve this issue in O(log n), but I don't see anything like it in the SQLite
format.




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