I have a search result overview of a custom page type that has more than 10.000 records in the system. I want to add an aggregated field to the index because I don't want to query per result in the overview. So on reindexing the search or on adding a new instance I want to make the query and add the result (string) to the index.
What is the best way to do this?

1. With an initialization module on the IndexingService.DocumentAdding event handler

2. Override the default SearchHandler in the IoC with a custom one

3. Create a separate job to call the UpdateIndex

In the first option it doesn't seem to hit my debugger. Is this available in Episerver 9 or is it legacy?