[BUG] Missing Fields in CSV Download for Object Arrays

[rayangou]

What is the bug?
When exporting data to CSV from a saved search that includes fields from a JSON object array (e.g., obj_field1: [{content: "test1"}, {content: "test2"}]), the specified fields (e.g., obj_field1.content) do not appear in the downloaded CSV file.

How can one reproduce the bug?
Steps to reproduce the behavior:

1. Create an index and upload documents formatted as obj_field1: [{content: "test1"}, {content: "test2"}].
2. In Discover, include the desired field (e.g., obj_field1.content) and save the search.
3. Generate the CSV report.
4. The field (e.g., obj_field1.content) will be missing from the CSV file.

What is the expected behavior?
The field (e.g., obj_field1.content) should be included in the CSV file.

What is your host/environment?

• OS: CentOS 7
• Version: OpenSearch 2.15 / OpenSearch Dashboards 2.15
• Plugins: Dashboards Reporting