json - kv filter in logstash -

how remove_field in kv work? have json file , need remove fields nested in json file.

[url][querystring][404;http://hspb.homesearch.com:80/wcjv4lhtsmzj1rx6foq4ruike k49gup2jvwtjdhhe] 1 such field

this filter doesn't work in logstash

 filter {    kv {       source => [ "[url][querystring]" ]       remove_field => [ "404;%{somefield}" "my_extraneous_field" ]     }   } 

remove_field remove named field(s) when underlying filter (in case 'kv') succeeds.

if need refer nested fields, try "[foo][bar]". can test if can use fields in variable names...

note: [foo][bar] meant illustrate how refer nested fields. if fields [mytopfield][mynestedfield], use that.