Checking if all tables can be checksummed ...
Starting checksum ...
--
-- osc.t2
--

REPLACE INTO `percona`.`checksums` (db, tbl, chunk, chunk_index, lower_boundary, upper_boundary, this_cnt, this_crc) SELECT ?, ?, ?, ?, ?, ?, COUNT(*) AS cnt, COALESCE(LOWER(CONV(BIT_XOR(CAST(CRC32(CONCAT_WS('#', convert(`c` using utf8mb4), CONCAT(ISNULL(`c`)))) AS UNSIGNED)), 10, 16)), 0) AS crc FROM `osc`.`t2` FORCE INDEX(`c`) WHERE (((? IS NULL OR `c` >= ?))) AND (((? IS NULL OR `c` <= ?))) /*checksum chunk*/

REPLACE INTO `percona`.`checksums` (db, tbl, chunk, chunk_index, lower_boundary, upper_boundary, this_cnt, this_crc) SELECT ?, ?, ?, ?, ?, ?, COUNT(*), '0' FROM `osc`.`t2` FORCE INDEX(`c`) WHERE ((((? IS NOT NULL AND `c` IS NULL) OR (`c` < ?)))) ORDER BY `c` /*past lower chunk*/

REPLACE INTO `percona`.`checksums` (db, tbl, chunk, chunk_index, lower_boundary, upper_boundary, this_cnt, this_crc) SELECT ?, ?, ?, ?, ?, ?, COUNT(*), '0' FROM `osc`.`t2` FORCE INDEX(`c`) WHERE ((((? IS NULL AND `c` IS NOT NULL) OR (`c` > ?)))) ORDER BY `c` /*past upper chunk*/

SELECT /*!40001 SQL_NO_CACHE */ `c`, `c` FROM `osc`.`t2` FORCE INDEX(`c`) WHERE (((? IS NULL OR `c` >= ?))) ORDER BY `c` LIMIT ?, 2 /*next chunk boundary*/

1 a,a b,b
2 b,b d,d
3 d,d g,g
4  a,a
5 g,g