Is there a major difference in ES5 queries and ES6?

Elastic Stack Elasticsearch
1

I am making a recommender with Elasticsearch. I know what people have bought and this forms the query. The index is of items and has a field that contains items bought in common.

In previous versions of ES (<= 5.6) the two queries below resulted in different scores and therefor different rankings

Here is what I found in ES 6.5

{
  "query": {
    "bool": {
      "should": [
        {
          "terms": {
            "bought": [
              "iPad Pro"
            ]
          }
        }
      ]
    }
  }
}

returns items, all with score = 1.0. This might make sense because each of the items has "iPad Pro" in its "bought" field.

But the following query:

{
  "query": {
    "bool": {
      "should": [
        {
          "terms": {
            "bought": [
              "iPad Pro",
              "iPhone 8"
            ]
          }
        }
      ]
    }
  }
}

also returns exactly the same items with scores of 1.0. This is not what I expected and does not make sense to me (it is also not what 5.6 did) because some items have both "iPad Pro" and "iPhone 8" and some only have 1 of these.

I would expect that the items that have both would score higher than those that have only one. It is as if this query is acting like a filter, not scoring by similarity to the query.

What am I doing wrong?

Does anyone know if there is a new ES query form for doing this type of thing? Wow I can't believe they made this big a change -- baffling.

2

I see other people have run into this. IMO bad choice for a change by ES but, oh well.

Should we be switching to a "terms_set" query in ES 6+ to replace the old "terms"? Does anyone know if it has exactly that same semantics as "terms" in ES 5?

3

Ok, this is the new behavior of the "terms" query. Yikes. Does anyone know is there is a new way to get the same scoring as the 5.6 version of "terms" this page does not say: https://www.elastic.co/guide/en/elasticsearch/reference/current/breaking-changes-6.0.html#_changes_to_queries

4

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