[Elasticsearch] Combine query clauses whenever possible to avoid deep nested BoolQuery

[rodrigozhou]

What changed?

Combining query clauses in Elasticsearch.

1. AND queries: combined multiple AND clause into a single BoolQuery. Example: a AND b AND c

• Before:

  {
    "bool": {
      "filter": [
        { ... }, // `a` clause
        {
          "bool": {
            "filter": [
              { ... }, // `b` clause
              { ... }  // `c` clause
            ]
          }
        }
      ]
    }
  }

• After:

  {
    "bool": {
      "filter": [
        { ... }, // `a` clause
        { ... }, // `b` clause
        { ... }  // `c` clause
      ]
    }
  }

2. OR queries: combined multiple OR clause into a single BoolQuery (similar to AND above)

3. NOT (a OR b): replace should with must_not.

• Before:

  {
    "bool": {
      "must_not": {
        "bool": {
          "should": [
            { ... }, // `a` clause
            { ... }  // `b` clause
          ]
        }
      }
    }
  }

• After:

  {
    "bool": {
      "must_not": [
        { ... }, // `a` clause
        { ... }  // `b` clause
      ]
    }
  }

4. a AND !b: combine filter and must_not clauses into a single BoolQuery.

• Before:

  {
    "bool": {
      "filter": [
        { ... }, // `a` clause
        {
          "bool": {
            "must_not": [
              { ... } // `b` clause
            ]
          }
        }
      ]
    }
  }

• After:

  {
    "bool": {
      "filter": [
        { ... } // `a` clause
      ]
      "must_not": [
        { ... } // `b` clause
      ]
    }
  }

Why?

Reduce nesting depth of bool queries.

How did you test it?

• built
• run locally and tested manually
• covered by existing tests
• added new unit test(s)
• added new functional test(s)

Potential risks