I am using the innodb storage engine for a table that is used for a lot
of SELECT's on columns that are defined as indexes. I have not enabled
the query cache as of now since the innodb buffer pool already caches
data and index information for InnoDB tables. So my question is - is
the query cache used primarily for MyISAM tables or is it also useful
for InnoDB tables (considering that the InnoDB has a buffer pool in
place)? If I do enable the query cache, is there an additional overhead
of maintaining two buffers that essentially contain the same data?