# 查询Haystack索引

> 弃用
>
> MongoDB 4.4不支持[geoHaystack](https://docs.mongodb.com/master/core/geohaystack/)索引和[ geoSearch ](https://docs.mongodb.com/master/reference/command/geoSearch/#dbcmd.geoSearch)命令。使用[2d索引](https://docs.mongodb.com/master/reference/operator/aggregation/geoNear/#pipe._S_geoNear)或[ $geoWithin ](https://docs.mongodb.com/master/reference/operator/query/geoWithin/#op._S_geoWithin)代替。

**Haystack**索引是一种特殊的**2d**地理空间索引，优化后可以在小区域内返回结果。要创建一个haystack索引，请参见[创建一个haystack索引](https://docs.mongodb.com/master/tutorial/build-a-geohaystack-index/#geospatial-indexes-haystack-index)。

要查询一个**haystack**索引，使用[ geoSearch ](https://docs.mongodb.com/master/reference/command/geosearch/#dbcmd.geosearch)命令。您必须为[geoSearch](https://docs.mongodb.com/master/reference/command/geosearch/#dbcmd.geosearch)指定坐标和附加字段。例如，要返回示例点附近的**type**字段中值为**restaurant**的所有文档，命令如下:

```
db.runCommand( { geoSearch : "places" ,
                 search : { type: "restaurant" } ,
                 near : [-74, 40.74] ,
                 maxDistance : 10 } )
```

> 注意
>
> **Haystack**索引不适合查询最接近特定位置的完整文档列表。与存储桶大小相比，最近的文档可能更远。
>
> 请注意
>
> haystack索引目前不支持[球形查询操作](https://docs.mongodb.com/master/tutorial/calculate-distances-using-sphery-geometry%20-with-2d-geospatial-indexes/)。
>
> [find()](https://docs.mongodb.com/master/reference/method/db.collection.find/#db.collection.find)方法不能访问**haystack**索引。


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# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.mongoing.com/indexes/geohaystack-indexes/query-a-haystack-index.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.