Logstash bulk update documens in ElasticSearch with WHERE conditon

Question

I have 2 tables in MySQL like this

Table DEPARTMENT

Id	Name
1	Department 1
2	Department 2

Table STAFF

Id	Department_Id	Name
1	1	Staff 1
2	1	Staff 2
3	2	Staff 3
4	1	Staff 4

• STAFF table has about 10 million records.

All STAFF's informations has been pushed by Logstash to ElasticSearch. Each document in ElasticSearch now only have 3 fields are Staff_Id, Staff_Name and Department_Name. Something like this:

{
    "Staff_Id": 1,
    "Staff_Name": "Staff 1",
    "Department_Name": "Department 1"
}

Because of practical needs, I need to add one more field called Department_Id to each document. Note that this field (Department_Id) does not exist on existing documents.

I am a newbie to both Logstash and ElasticSearch. How can I do this with Logstash? Interpreted in the SQL way would be:

• SELECT * FROM DEPARTMENT;
• UPDATE STAFF SET Department_Id = XXX WHERE Department_Name = YYY

Note that DEPARTMENT table has about 100.000 records and ElasticSearch has about 10 million documents. Can you take a look?