Logstash not updating Data as schedule

@magnusbaeck ,
I m continuously migrating data from MySQL to elastic search through scheduling via logstash. Everything is working fine and data is indexed in ES. But when i update 4 to 5 records it will update 3 and remaing 2 are not updated in ES.
Following is my configuration file.

> input{
> jdbc {
> jdbc_connection_string => "----"
> jdbc_user => "------"
> jdbc_password => "-----------"
> jdbc_validate_connection => true
> #jdbc_driver_library => "/home/ubuntu/mysql-connector-java-5.1.36-bin.jar"
> jdbc_driver_class => "com.mysql.jdbc.Driver"
> tracking_column => "updated_timestamp"
> tracking_column_type => "timestamp"
> use_column_value => true
> jdbc_default_timezone => "UTC"
> schedule => "* * * * * *"
> statement => "SELECT
> id as db_id,
> DATE_FORMAT(updated_timestamp, '%Y-%m-%d %T') as updated_timestamp,
> CONCAT('u','-', following_id) as user_id,
> created_at,
> CONCAT('fg','-', id) as id,
> CONCAT('u','-', follower_id) as object_id,
> id,
> status
> FROM
> friends
> WHERE
> updated_timestamp > :sql_last_value order by updated_timestamp DESC "
> last_run_metadata_path => "/home/ubuntu/logstash_track_date/.logstash_followings_jdbc_last_run"
> add_field => { "doctype" => "followings" }
> }
> }

Any help is much appreciated.