Add ability to specify minimum score for fulltext index search

[darrellwarde]

Is your feature request related to a problem? Please describe.

Full-text searches can return a lot of results, and filtering on the search score can help minimise the results.

Describe the solution you'd like

It should be possible to set a default value for this, and also override it per query.

For instance, this could be applied to a type like so:

type Movie @fulltext(name: "MovieTitle", fields: ["title"], defaultMinimumScore: 1) {
  title: String!
}

And also when querying like so:

query {
  movies(fulltext: { MovieTitle: { phrase: "Forrest", minimumScore: 2 } }) {
    title
  }
}

EDIT: another option is allowing minimum and maximum:

query {
  movies(fulltext: { MovieTitle: { phrase: "Forrest", score: { min: 2, max: 50 } } }) {
    title
  }
}

Additional context

An attempt at this functionality was removed in #1196, because the implementation was flawed in that it checked for an exact score match rather than a minimum.

[trondaal]

What about just adding the score returned from db.index.fulltext to the returned node in some way? Access to the score value would enable any user defined logic to be implemented.

[darrellwarde]

What about just adding the score returned from db.index.fulltext to the returned node in some way? Access to the score value would enable any user defined logic to be implemented.

I think that's a good idea in principle, but I think it will be a very messy addition to just add it into the returned node. I've raised an issue #1373 to capture how we might do this in future.

[darrellwarde]

This feature is now supported if you use the root-level queries generated for full-text indexes.