indexing - Can I force merge index in Mysql -


i have query looking 

select fld table id > 50000  , fld_1 = 0  limit 1000

both id , fld_1 indexed. using either 1 of them better result? force index using 1 of them.

i referring - http://dev.mysql.com/doc/refman/5.1/en/index-merge-optimization.html#index-merge-intersection

i don't know of way force index-merge. conditions on manual page describe conditions when index-merge can done, , optimizer should automatically if can (and if cost-based optimizer decides it's worth so). can't force index-merge if it's not possible.

but compound index performs better index-merge anyway, better strategy.

the order of columns matters. put columns equality comparisons first in index, columns inequality comparisons.

create index idxfld1id on `table` (fld_1, id);

see presentation how design indexes, really.

you can make schema changes such creating indexes -- without downtime -- using http://www.percona.com/doc/percona-toolkit/pt-online-schema-change.html

of course, first try on test copy of database, learn how use tool.


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