… table: utest type: index_merge possible_keys: c1,c2 key: c1,c2 key_len: 4,4 ref: NULL rows: 162380 Extra: Using sort_union… see MySQL 5.1.21 uses sort_merge to access the rows but it can’t use it together with order by efficiently. I….0 solution – using UNION instead of single query works in this case: mysql> explain (select * from utest where c1=5) union (select * from…
Post: Possible optimization for sort_merge and UNION ORDER BY LIMIT
September 18, 2007 By 10 Comments
Post: Distributed Set Processing with Shard-Query
May 14, 2011 By 27 Comments
…union of all the already joined and aggregated data from all the nodes. A single temporary table is used…problems and then putting the results back together again. This set logic allows to …* on the base table: `origin_airport_id` * storage node result set merge optimization enabled: ON DUPLICATE…
