Using map. No need to run query again
Merge pull request #10557 from arunagw/pluck-refactor-using-map

Using map. No need to run query again
Fix test to ruby 2.0

The default enconding changed on Ruby 2.0
So not make Fixnum#/ private on Ruby verions less than 1.9.3

In those version to_date call Fixnum#/, what will cause a failure
Revert "Don't try to EXPLAIN select_db calls"

Reason: This was backported, but the test does not pass as is.

This reverts commit a33d320cf4b57fabd9c299b09c217ee3955ecc77.