…of rows returned by the query but number of rows accessed by the query will most likely be defining query performance. Of… to reach for small fraction of queries. If you’re joining multiple tables or if you …USA’ As of MySQL 5.0 MySQL will materialize the subquery in the from clause fully and so “use…
Comment: How expensive is a WHERE clause in MySQL?
August 4, 2010 By 17 Comments
… the JOIN size. Because the other side of the JOIN already limited the records as needed, the WHERE clause on the first subquery was unneeded. I assumed that having a smaller resultset would increase performance because less memory was copied and used; however…
Comment: My Innodb Feature wishes
May 13, 2006 By 30 Comments
… your case join can be only performed using …of rows query would return without subselect: mysql> select count(*) from Statement T join CurrDailyVal Q on Q.cur1 = T.cur and Q.cur2 = “EUR”; +———-+ | count(*) | +———-+ | 55125114 | +———-+ 1 row in set (1 min 17.06 sec) This subquery…
Comment: Air traffic queries in InfiniDB: early alpha
November 3, 2009 By 19 Comments
Vadim – Thanks for including us in your tests! One of our engineers will be following up with you shortly on … of subquery support, I agree with you on the need. We decided to implement hash joins in the engine first (which are in) and then come back to do subqueries that perform much better than…
Post: Extended EXPLAIN
July 24, 2006 By 9 Comments
…test`.`sbtest` `t1` join `test`.`sbtest` `t2` where ((`test`.`t2`.`k` = `test`.`t1`.`k`) and (`test`.`t1`.`id… subquery manually and use IN (1,2,3,…10) it completes in tiny fraction of the second. Anyway EXPLAIN EXTENDED is very valuable addition to EXPLAIN for MySQL Performance…
Post: Watch out for Marketing benchmarks
August 23, 2006 By 7 Comments
… MySQL sucks and you better to do things differently or use other database. For example it happens with many types of subqueries, cases when hash or sort merge join is needed and in many other advanced optimizer features… benchmarked of MySQL vs PostgreSQL and try my best to get best performance out of both of them, I still know MySQL much better and so…
