logstash-input-jdbc:string is too long to be intercepted when synchronizing data into ES with using mysql "group_concat" function

string is too long to be intercepted when synchronizing data into ES by plugin jdbc with using mysql "group_concat" function :

Version: logstash 2.3.1

Operating System: centos7

Sample Data:
1，sql:select id,group_concat(str) as long_str from long_str_test
2，long_str‘s length longer than 350 characters
3，import into ES by plugin jdbc，the long_str be intercepted, length is 343.

Steps to Reproduce:
1，sql:select id,group_concat(str) as long_str from long_str_test
2，long_str‘s length longer than 350 characters
3，import into ES by plugin jdbc，the long_str be intercepted, length is 343.