Allow multiple collections

[gforcada]

Solr is great, but it has a few downsides:

• if you upgrade to a new version: you must reindex all your content
• if you change the schema: you must reindex all your content
• ...

... and that's specially hurting if reindexing the complete website takes a sizeable amount of time (for us around 24h hours).

💡 One mitigation strategy we have been using is to make the changes on non-production environment, and as soon as the critical amount of content has been reindexed, move Solr data from non-production to production and finish the reindexing there.

Another strategy that I read somewhere (probably on the solr docs) is to configure a second parallel collection, do the full reindex there (while the existing collection is still being used), and whenever reindexing has catch-up, switch them over ✨

Would that be something that could be done within collective.solr ? 🤔

[davisagli]

@gforcada I was thinking about the same thing, but haven't had a chance to work on it. I think a key thing to solve is making sure that the indexing of the new collection has a way to catch up with changes to any documents that are modified during the reindex process.