[MEVD] [PG] Implement hybrid search support

[roji]

See this for an example. There doesn't seem to be a proper ranking function (RRF), but the approach used there of simply adding both scores may be good enough?

/cc @westey-m assigning to you for now, let's see if this makes sense for Build etc...

[westey-m]

@roji, I didn't include PG in the original hybrid search implementation set since it requires a language for to_tsvector.
I think this makes sense to add once we support custom per DB metadata, so that we have a way to pass the language per property.

[roji]

Makes sense, I missed that aspect.

One thought (for later) is to require the user to provide the language in a connector-specific annotation (in the record definition), and that gets embedded in the SQL. Or maybe it makes sense to make this a strongly-typed property for all connectors.

[westey-m]

One thought (for later) is to require the user to provide the language in a connector-specific annotation (in the record definition)

Yes, that's what I'm thinking too.

Or maybe it makes sense to make this a strongly-typed property for all connectors.

This setting doesn't seem to be super common. Cosmos DB has something similar, but it's a locale instead of a language so the format varies here too. Therefore I'm thinking it probably makes more sense as a DB specific Attribute + Metadata.

[roji]

Listed this as a possible case in #10359.