… partial matches like ‘abc%’. But we’re talking here about mysql behaviour. I suspect that in your case the cardinality of… without losing any performance. And there’s the problem of mysql choosing single column indexes where multi-column indexes are present… that single column indexes make more sense in mysql most of the time. Index intersection should be more efficient than multi-column…
Comment: Multi Column indexes vs Index Merge
June 1, 2010 By 31 Comments
… 7. 1 row IN SET (0.00 sec) 1. mysql [localhost] {msandbox} (test)> EXPLAIN SELECT avg(… | i2,i1 | 4,4 | NULL | 959 | USING intersect(i2,i1); USING WHERE | 6. +—-+————-+———+————-+—————-+——-+———+——+——+————————————-+ 7….
Comment: Using UNION to implement loose index scan in MySQL
August 11, 2006 By 15 Comments
…, This is not the case where index merge can apply: mysql> explain SELECT SQL_NO_CACHE name FROM people WHERE age… or to intersect row pointers from both indexes. If you would need OR in this case Index merge would apply. mysql> explain…
Comment: Full text search for all MySQL Storage Engines
June 29, 2006 By 37 Comments
… MySQL performance you’re right. There are two pieces which slow things down. First finding the rows which contain all keywords. Intersection of pretty large sets needs to be performed. Next problem is sorting – it is done by MySQL rather than…
Comment: MySQL Query Cache
November 17, 2009 By 70 Comments
… has it)” Consider this query, given that Visit is the intersection entity between Consultant and Student (one-many-one): SELECT Consultant…, caching all the objects might take more memory than letting MySQL caching the raw data.
