# Why query\_string doesn't honor the usual precedence rules?

**URL:** <https://discuss.elastic.co/t/why-query-string-doesnt-honor-the-usual-precedence-rules/248779>\
**Category:** Elasticsearch\
**Created:** [September 16, 2020, 7:13am UTC](https://discuss.elastic.co/t/why-query-string-doesnt-honor-the-usual-precedence-rules/248779 "2020-09-16T07:13:50Z")\
**Posts on this page:** 5\
**Page:** 1

<div class="post-metadata">

**Author:** ![android.kc](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/android.kc/32/58806_2.png) [@android.kc](https://discuss.elastic.co/u/android.kc)\
**Post date:** [September 16, 2020, 7:13am UTC](https://discuss.elastic.co/t/why-query-string-doesnt-honor-the-usual-precedence-rules/248779/1 "2020-09-16T07:13:51Z")

</div>

Can anyone please explain why I got all different results in the following query\_string queries (all are the same except the parentheses)

1. A OR B AND C

2. (A OR B) AND C

3. A OR (B AND C)

The index only has the three documents in total details as below, #1 and #3 are expected to have the same result, but all the three are different.

but actual result:  
#1 returns only 1 doc  
#2 returns 2 docs  
#3 returns all the 3 docs

Here is the test case

```
{
  "took": 5,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 3,
    "max_score": 0.5753642,
    "hits": [
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00IB737J1OF7D8RB4TUJ42LAES0082HF",
        "_score": 0.5753642,
        "_source": {
          "A": "3100007",
          "B": "Routed"
        }
      },
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00MJOP7K6OF7D1SA51UJ42LAES005PIJ",
        "_score": 0.2876821,
        "_source": {
          "A": "3100000",
          "B": "Terminated"
        }
      },
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00THNBNJVCF7D2PI51MJ42LAES005LV1",
        "_score": 0.2876821,
        "_source": {
          "A": "3100000",
          "B": "Routed"
        }
      }
    ]
  }
}

```

For **A OR B AND C**

Query:

```auto
POST testquery/_search
{
  "query": {
      "query_string": {
            "query": "A.keyword:3100000 OR A.keyword:3100007 AND B.keyword:Routed"
      }
  }
}

```

Result:

```auto
{
  "took": 4,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 1,
    "max_score": 0.5753642,
    "hits": [
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00IB737J1OF7D8RB4TUJ42LAES0082HF",
        "_score": 0.5753642,
        "_source": {
          "A": "3100007",
          "B": "Routed"
        }
      }
    ]
  }
}

```

For **(A OR B) AND C**

Query

```auto
POST testquery/_search
{
  "query": {
    "query_string": {
      "query": "(A.keyword:3100000 OR A.keyword:3100007) AND B.keyword:Routed"
    }
  }
}

```

Results

```auto
{
  "took": 6,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 2,
    "max_score": 0.5753642,
    "hits": [
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00IB737J1OF7D8RB4TUJ42LAES0082HF",
        "_score": 0.5753642,
        "_source": {
          "A": "3100007",
          "B": "Routed"
        }
      },
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00THNBNJVCF7D2PI51MJ42LAES005LV1",
        "_score": 0.5753642,
        "_source": {
          "A": "3100000",
          "B": "Routed"
        }
      }
    ]
  }
}

```

For **A OR (B AND C)**  
Query

```auto
POST testquery/_search
{
  "query": {
    "query_string": {
      "query": "A.keyword:3100000 OR (A.keyword:3100007 AND B.keyword:Routed)"
    }
  }
}

```

Results

```auto
{
  "took": 3,
  "timed_out": false,
  "_shards": {
    "total": 5,
    "successful": 5,
    "skipped": 0,
    "failed": 0
  },
  "hits": {
    "total": 3,
    "max_score": 0.5753642,
    "hits": [
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00IB737J1OF7D8RB4TUJ42LAES0082HF",
        "_score": 0.5753642,
        "_source": {
          "A": "3100007",
          "B": "Routed"
        }
      },
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00MJOP7K6OF7D1SA51UJ42LAES005PIJ",
        "_score": 0.2876821,
        "_source": {
          "A": "3100000",
          "B": "Terminated"
        }
      },
      {
        "_index": "testquery",
        "_type": "_doc",
        "_id": "00THNBNJVCF7D2PI51MJ42LAES005LV1",
        "_score": 0.2876821,
        "_source": {
          "A": "3100000",
          "B": "Routed"
        }
      }
    ]
  }
}

```

---

<div class="post-metadata">

**Author:** ![android.kc](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/android.kc/32/58806_2.png) [@android.kc](https://discuss.elastic.co/u/android.kc)\
**Post date:** [September 17, 2020, 4:15pm UTC](https://discuss.elastic.co/t/why-query-string-doesnt-honor-the-usual-precedence-rules/248779/2 "2020-09-17T16:15:25Z")

</div>

Does anyone have any idea, or it's a defect?

---

<div class="post-metadata">

**Author:** ![Mark\_Harwood](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/mark_harwood/32/10538_2.png) [@Mark\_Harwood](https://discuss.elastic.co/u/Mark_Harwood)\
**Post date:** [September 18, 2020, 8:57am UTC](https://discuss.elastic.co/t/why-query-string-doesnt-honor-the-usual-precedence-rules/248779/3 "2020-09-18T08:57:46Z")

</div>

I had a look into this using the [validate query](https://www.elastic.co/guide/en/elasticsearch/reference/current/search-validate.html) API.

Here's the command to debug `aa OR bb AND cc`:

```
GET githubcommits/_validate/query?q=aa+OR+bb+AND+cc&rewrite=true&df=myfield

```

The result is:

```
  "explanation" : "myfield:aa +myfield:bb +myfield:cc"

```

Lucene's Boolean query has the idea of mandatory `must` clauses and `should` clauses which are just nice-to-haves. In the above query `aa` is relegated to a wholly optional `should` clause that gives extra scoring points to documents that contain both of the mandatory `must` clauses bb and cc.  
If you want to have pure OR clauses in Lucene you need to use a Boolean query with `should` clauses but no `must` clauses. Something like this:

```
bool
    should
         aa
         bool
              must
                  bb
                  cc

```

Note the use of a nested bool query above to get the required logic.  
The introduction of brackets in query\_string syntax forces the creation of these sub boolean clauses and makes the logic behave in a more predictable way.

Weird, but I'd hesitate to call it a bug - more a quirk of Lucene.  
For readability's sake alone I would advocate using brackets to make the logic clear.

---

<div class="post-metadata">

**Author:** ![android.kc](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/android.kc/32/58806_2.png) [@android.kc](https://discuss.elastic.co/u/android.kc)\
**Post date:** [September 18, 2020, 4:36pm UTC](https://discuss.elastic.co/t/why-query-string-doesnt-honor-the-usual-precedence-rules/248779/4 "2020-09-18T16:36:25Z")

</div>

Thank you very much for the great explanation! it makes more sense now. will use brackets as you suggested!

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [October 16, 2020, 4:36pm UTC](https://discuss.elastic.co/t/why-query-string-doesnt-honor-the-usual-precedence-rules/248779/5 "2020-10-16T16:36:27Z")

</div>

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