##Solution
Delete the existing Azure Search index (`sitecore-master-index`, in this case) before rebuilding the index.

##Why?
The rebuild process does not recreate the index (at least not initially) so if your index was already built with many other fields, it won't clear those out before building it fresh.

## How
If you don't have Switch On Rebuild enabled, you can simply navigate to that index in your Azure portal and delete it.

If you _do_ have Switch On Rebuild enabled, in order to minimize impact to your application, you should delete the index that is currently set to be secondary (known as the "rebuild" index). **Note:** this does not mean simply deleting the `sitecore-master-index-secondary` index; that could be the active one.

### To figure out the current "rebuild" index
1. Open an Azure Query Editor instance to your core db (`*-core-db`)
1. Run the below query:
 ```
 SELECT * FROM Properties
 WHERE [Key] LIKE '%sitecore_master%_cloud_rebuild_index_name'
 ```

[![example results from query editor][1]][1]


 [1]: https://i.sstatic.net/bhr1Y.png