Hi,
I think your filter is fine, but you need to use 'filter' and not 'must'. I did something similar to try and it worked fine, here's my filter:
and here's how the request looks like:
Let me know if it's helfpul!
© 2020. All Rights Reserved - Elasticsearch
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.