Error in reading data

Elastic Stack Logstash
1

I am using Logstash 5.3. and connecting to Oracle database.I gave a select query with values for 1 year.It worked fine but suddenly when i run logstash it starts overwriting the values.Example:February's data is overwritten over January's data.
The same happens for all months.All months data is getting overwritten with January's data

Can anybody help me with this issue?

2

Can you paste your config?

3

In filter plugin i gave format as dd-mm-yyyy it worked for sometime and suddenly it started overwriting.

I changed the format now to yyyy-mm-dd and its working fine.

Can i know why logstash suddenly stopped accepting that date format