Amazon OpenSearch (ElasticSearch) Piped Processing Language, "where" command - How to Filter for "some_field is not null"

Question

I am building a Notebook in AWS OpenSearch (formerly Amazon elasticsearch) and I want to provide a condition to the "where" command excluding documents where a particular field is not null.

In SQL this would simply be "where my_field is not null" however, The notebook indicates a syntax error where this condition is added to the where command.

Answer 1

This worked

where length(my_field)>0

From Open Distro for Elasticsearch function docs here and here.