I'm trying to set up a multisite search across several legacy Drupal 7 sites that use the Apache Solr search module.
I'm doing this by using a shared core that all the sites will index to, and a further site will be used for searching.
Some of these sites already use Solr for searching, so I figured I'd add the shared core as a second core, so that any site specific search configurations would not be disrupted, and I could index other content types that the existing config has excluded.
The problem I've hit is that content doesn't get sent to the second core. Deleting, queuing and reindexing content all apply to the first core only, and I haven't found a way to have both cores being indexed.
Is there a way I can do this?