Logstash jdbc plugin understanding

Question

Can anyone explain what does add_field do ?

filter {
mutate {
add_field => { "%{column1}" => "column2" }
}
}

What is the difference between add_field present in mutate, clone, kv and grok plugins

Answer 1

With this config, add_fields adds a new field to the message, the fieldname will be equal to the value of the 'column1' field in the input, and its value will be the litteral 'column2'. If you want the value to be the value of the input field, you have to use %{column2}