a problem about auto_increase

i have 1 logical table ,separate into 2 physical tables ,put them into 2 database .
then make the 2 database as 2 datanode into cobar.

the table have 1 column 'id' auto_increase.
use the rule :

2
512

when i insert 1 row into cobar without special id, cobar generate 2 row in 2 database

Start by reproducing the insert through Cobar with the two datanodes and the shown func1 PartitionByLong rule, using a table whose id is auto_increase. Trace the routing and generated-key behavior; done means the insert produces the intended single row rather than duplicate rows in both databases.

Written by the indexing model from the issue text.