On 4/8/15, Dominique Devienne <ddevienne at gmail.com> wrote: > With a LIMIT clause, in > such a GROUP BY ORDER BY returning a large result set, would SQLite: > 1) sort the whole result-set and then keep only the first top-N rows? > 2) or instead do a partial-sort of the first top-N rows only,
SQLite must examine all rows of output, obviously. But it only keeps the top-N in memory and only sorts the top-N. If there are a total of M candidate rows and only the top-N are to be displayed, then the algorithm is O(M*logN) in time and O(N) in space. -- D. Richard Hipp drh at sqlite.org
