[jsonstring][issuer] means "the field jsonstring with the subfield issuer", i.e. a JSON document that looks like this:
{
...
"jsonstring": {
"issuer": "..."
}
}
That's not what you have. You have a jsonstring field containing the string "issuer=r". I suggest you use a kv filter to parse that string and create the issuer field.
Apache, Apache Lucene, Apache Hadoop, Hadoop, HDFS and the yellow elephant
logo are trademarks of the
Apache Software Foundation
in the United States and/or other countries.