GridDB does not natively support querying nested JSON values directly within a STRING column. The current capabilities of GridDB for handling JSON payloads stored as strings do not include querying nested elements within the JSON. The approach you are currently using—selecting all rows, parsing the JSON in Java, and then filtering manually—is the typical method for dealing with JSON data stored as strings in GridDB.

If you require the ability to query nested JSON values efficiently, you may need to consider a different database system that has built-in support for JSON data types and allows querying of nested JSON elements directly, such as MongoDB. MongoDB, for example, provides powerful querying capabilities for JSON documents, including the ability to query nested fields.

In summary, with GridDB, you will need to handle JSON parsing and filtering within your application code, as native querying of nested JSON is not supported.