Aggregation with a minimum searchScore

MongoDB Atlas Atlas Search
,
1

Hi, we’re using Atlas Search in some sort of this way:

[
  {
    $search: {
      index: "search_person",
      compound: {
        should: [
          {
            text: {
              query: "robin",
              path: "name",
            },
          },
          {
            text: {
              query: "robin",
              path: ["iban", "email"],
              score: {
                boost: {
                  value: 10,
                },
              },
            },
          },
        ],
      },
      sort: {
        _score: {
          $meta: "searchScore",
          order: -1,
        },
        createdAt: 1,
        _id: -1,
      },
    },
  },
  {
    $addFields: {
      _score: {
        $meta: "searchScore",
      },
    },
  },
]

But now we want to filter on searchScore greater than 10.

Adding a $match stage after the $search inside the aggregation makes it (obviously) very slow:

  {
    $match: {
      _score: {
        $gte: 10
      },
    },
  }

The documentation recommends to use filter instead of $match inside the compound, but I think I don’t have searchScore available at that point? Otherwise I could have tried with a range.

Thank you in advance.

Kinds regards,
Robin van Wijngaarden

2

Hi, Search PM here. We don’t support this out of the box. Can you explain why you are trying to do this?

3

Hi Elle,

Thanks for your swift reply!

A lot of applications use offset pagination, but in our product we’re using cursor-based pagination. That means we need to have a non-deterministic way of generating the results.

For example: on page 1 with 10 results, the top one has the highest searchScore and the 10th result will have something like 87.48239. Then the first result on page 2 should start with 87.48239 and lower. That’s the reason I’m asking for a $gt or $lt option on searchScore without using $match (because that’s slow).

I hope this makes our usecase more clear.

4

Ah ok, we are delivering an in-search cursor based pagination solution early next year that when used with sorting by score I believe would do exactly as you’re describing. I wonder if there is some sort of solution in the meantime that can be used just leveraging our sort by score functionality.

5

FYI in-search cursor based pagination is now available. See docs here.