# Why match\_bool\_prefix with a query with trailing space will generate different results

**URL:** <https://discuss.elastic.co/t/why-match-bool-prefix-with-a-query-with-trailing-space-will-generate-different-results/360673>\
**Category:** Elasticsearch\
**Created:** [June 2, 2024, 3:14pm UTC](https://discuss.elastic.co/t/why-match-bool-prefix-with-a-query-with-trailing-space-will-generate-different-results/360673 "2024-06-02T15:14:12Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![bigpotato](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/bigpotato/32/134982_2.png) [@bigpotato](https://discuss.elastic.co/u/bigpotato)\
**Post date:** [June 2, 2024, 3:14pm UTC](https://discuss.elastic.co/t/why-match-bool-prefix-with-a-query-with-trailing-space-will-generate-different-results/360673/1 "2024-06-02T15:14:12Z")

</div>

The index mapping:

```auto
"orgName": {
                    "type": "text",
                    "fields": {
                        "keyword": {
                            "type": "keyword",
                            "ignore_above": 256
                        }
                    }
                }

```

Part of my query like this :

```auto
{
          "bool": {
            "should": [
              {
                "match_bool_prefix": {
                  "orgName": {
                    "query": "island",
                    "operator": "AND",
                    "prefix_length": 0,
                    "max_expansions": 50,
                    "fuzzy_transpositions": true,
                    "boost": 1.0,
                  }
                }
              }
            ],
            "adjust_pure_negative": true,
            "boost": 1.0
          }
        }

```

But if I change the query to "island " with a trailing space, it will generate different results, specifically it calculate the score in different ways.

For the query without trailing space, the score is calculated as :

```auto
"value" : 1.0
"description": "orgName:island*",
"details": []

```

But for the query with trailing space, it is calculated as this:

```auto
    "value": 10.185921,

                            "description": "weight(orgName:island in 45462) [PerFieldSimilarity], result of:",

                            "details": [

                                {

                                    "value": 10.185921,

                                    "description": "score(freq=2.0), computed as boost * idf * tf from:",

                                    "details": [

                                        {

                                            "value": 2.2,

                                            "description": "boost",

                                            "details": []

                                        },

                                        {

                                            "value": 6.9498363,

                                            "description": "idf, computed as log(1 + (N - n + 0.5) / (n + 0.5)) from:",

                                            "details": [

                                                {

                                                    "value": 23,

                                                    "description": "n, number of documents containing term",

                                                    "details": []

                                                },

                                                {

                                                    "value": 24509,

                                                    "description": "N, total number of documents with field",

                                                    "details": []

                                                }

                                            ]

                                        },

                                        {

                                            "value": 0.6661975,

                                            "description": "tf, computed as freq / (freq + k1 * (1 - b + b * dl / avgdl)) from:",

                                            "details": [

                                                {

                                                    "value": 2.0,

                                                    "description": "freq, occurrences of term within document",

                                                    "details": []

                                                },

                                                {

                                                    "value": 1.2,

                                                    "description": "k1, term saturation parameter",

                                                    "details": []

                                                },

                                                {

                                                    "value": 0.75,

                                                    "description": "b, length normalization parameter",

                                                    "details": []

                                                },

                                                {

                                                    "value": 4.0,

                                                    "description": "dl, length of field",

                                                    "details": []

                                                },

                                                {

                                                    "value": 5.127382,

                                                    "description": "avgdl, average length of field",

                                                    "details": []

                                                }

                                            ]

                                        }

                                    ]

                                }

                            ]

```

---

<div class="post-metadata">

**Author:** ![Kathleen\_DeRusso](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/kathleen_derusso/32/132039_2.png) [@Kathleen\_DeRusso](https://discuss.elastic.co/u/Kathleen_DeRusso)\
**Post date:** [June 10, 2024, 5:59pm UTC](https://discuss.elastic.co/t/why-match-bool-prefix-with-a-query-with-trailing-space-will-generate-different-results/360673/2 "2024-06-10T17:59:57Z")

</div>

The match bool prefix query parses the input and creates a boolean query from each term. The parser sees a space as another term is coming, so it constructs the query differently though the end result is correct.

---

<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:** [July 8, 2024, 6:00pm UTC](https://discuss.elastic.co/t/why-match-bool-prefix-with-a-query-with-trailing-space-will-generate-different-results/360673/3 "2024-07-08T18:00:50Z")

</div>

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