Now, the checksum field is a CHAR(32) instead of a BIGINT.
Previously it was failing on some MySQL versions since the truncated int
it was storing is not consistent. Now, by having an MD5 stored as a
CHAR(32) the checksum is consistent across MySQL and OS versions.
This is a breaking change and pt-query-digest history and review tables
are not backwards compatible.
f95d448e03