

What's new in MySQL 5.7 - ck2
http://dev.mysql.com/doc/relnotes/mysql/5.7/en/news-5-7-2.html

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ck2
I cannot wait for the SELECT COUNT( _) improvements for innodb, I hope Percona
backports them into 5.6

    
    
        For SELECT COUNT (*) queries, where a table's committed record count is changed by transaction deltas, 
        there is now a single handler call to the storage engine to return the record count to the optimizer instead of one call for each record. 
        This change generally improves SELECT COUNT (*) query performance and reduces in-memory table scan cost, as each record is no longer returned to the optimizer.

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gmuslera
It seem to imply creating new structures in files. You will need the
upgrade_mysql or similar script for doing so, odds are low that it will happen
keeping the same version number.

There are also too many things in this version that are incompatible changes
that requires upgrading the db, doing a small patch to upgrade individual
feature could complicate things when comes the time to upgrade to 5.7+.

