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Document '_name' field in 'function_score' query's function definition #7340

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Jul 9, 2024
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Document '_name' field in 'function_score' query's function definition #7340

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Document '_name' field in 'function_score' query function definition
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196 changes: 195 additions & 1 deletion _query-dsl/compound/function-score.md
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Expand Up @@ -826,4 +826,198 @@ The results contain the three matching blog posts:
}
}
```
</details>
</details>

## Named functions

When defining a function, you can specify its name using the `_name` parameter at the top level. This name is useful for debugging and understanding the scoring process. Once specified, the function name is included in the score calculation explanation whenever possible (this applies to functions, filters, and queries). You can identify the function by its `_name` in the response.

### Example

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The following request sets `explain` to `true` for debugging purposes in order to obtain scoring explanation in the response. Each function contains a `_name` parameter so you can identify the function unambiguously:

```json
GET blogs/_search
{
"explain": true,
"size": 1,
"query": {
"function_score": {
"functions": [
{
"_name": "likes_function",
"script_score": {
"script": {
"lang": "painless",
"source": "return doc['likes'].value * 2;"
}
},
"weight": 0.6
},
{
"_name": "views_function",
"field_value_factor": {
"field": "views",
"factor": 1.5,
"modifier": "log1p",
"missing": 1
},
"weight": 0.3
},
{
"_name": "comments_function",
"gauss": {
"comments": {
"origin": 1000,
"scale": 800
}
},
"weight": 0.1
}
]
}
}
}
```
{% include copy-curl.html %}

The response explains the scoring process. For each function, the explanation contains the function `_name` in its `description`:

<details open markdown="block">
<summary>
Response
</summary>
{: .text-delta}

```json
{
"took": 14,
"timed_out": false,
"_shards": {
"total": 1,
"successful": 1,
"skipped": 0,
"failed": 0
},
"hits": {
"total": {
"value": 3,
"relation": "eq"
},
"max_score": 6.1600614,
"hits": [
{
"_shard": "[blogs][0]",
"_node": "_yndTaZHQWimcDgAfOfRtQ",
"_index": "blogs",
"_id": "1",
"_score": 6.1600614,
"_source": {
"name": "Semantic search in OpenSearch",
"views": 1200,
"likes": 150,
"comments": 16,
"date_posted": "2022-04-17"
},
"_explanation": {
"value": 6.1600614,
"description": "function score, product of:",
"details": [
{
"value": 1,
"description": "*:*",
"details": []
},
{
"value": 6.1600614,
"description": "min of:",
"details": [
{
"value": 6.1600614,
"description": "function score, score mode [multiply]",
"details": [
{
"value": 180,
"description": "product of:",
"details": [
{
"value": 300,
"description": "script score function(_name: likes_function), computed with script:\"Script{type=inline, lang='painless', idOrCode='return doc['likes'].value * 2;', options={}, params={}}\"",
"details": [
{
"value": 1,
"description": "_score: ",
"details": [
{
"value": 1,
"description": "*:*",
"details": []
}
]
}
]
},
{
"value": 0.6,
"description": "weight",
"details": []
}
]
},
{
"value": 0.9766541,
"description": "product of:",
"details": [
{
"value": 3.2555137,
"description": "field value function(_name: views_function): log1p(doc['views'].value?:1.0 * factor=1.5)",
"details": []
},
{
"value": 0.3,
"description": "weight",
"details": []
}
]
},
{
"value": 0.035040613,
"description": "product of:",
"details": [
{
"value": 0.35040614,
"description": "Function for field comments:",
"details": [
{
"value": 0.35040614,
"description": "exp(-0.5*pow(MIN[Math.max(Math.abs(16.0(=doc value) - 1000.0(=origin))) - 0.0(=offset), 0)],2.0)/461662.4130844683, _name: comments_function)",
"details": []
}
]
},
{
"value": 0.1,
"description": "weight",
"details": []
}
]
}
]
},
{
"value": 3.4028235e+38,
"description": "maxBoost",
"details": []
}
]
}
]
}
}
]
}
}
```
</details>

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As you can see, the explanation contains the name in the respective function's description.
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