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115 lines
4.0 KiB
Markdown
115 lines
4.0 KiB
Markdown
---
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sidebar_label: Geohash
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---
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# Functions for Working with Geohash
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[Geohash](https://en.wikipedia.org/wiki/Geohash) is the geocode system, which subdivides Earth’s surface into buckets of grid shape and encodes each cell into a short string of letters and digits. It is a hierarchical data structure, so the longer is the geohash string, the more precise is the geographic location.
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If you need to manually convert geographic coordinates to geohash strings, you can use [geohash.org](http://geohash.org/).
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## geohashEncode
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Encodes latitude and longitude as a [geohash](#geohash)-string.
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``` sql
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geohashEncode(longitude, latitude, [precision])
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```
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**Input values**
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- longitude - longitude part of the coordinate you want to encode. Floating in range`[-180°, 180°]`
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- latitude - latitude part of the coordinate you want to encode. Floating in range `[-90°, 90°]`
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- precision - Optional, length of the resulting encoded string, defaults to `12`. Integer in range `[1, 12]`. Any value less than `1` or greater than `12` is silently converted to `12`.
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**Returned values**
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- alphanumeric `String` of encoded coordinate (modified version of the base32-encoding alphabet is used).
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**Example**
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``` sql
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SELECT geohashEncode(-5.60302734375, 42.593994140625, 0) AS res;
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```
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``` text
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┌─res──────────┐
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│ ezs42d000000 │
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└──────────────┘
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```
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## geohashDecode
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Decodes any [geohash](#geohash)-encoded string into longitude and latitude.
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**Input values**
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- encoded string - geohash-encoded string.
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**Returned values**
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- (longitude, latitude) - 2-tuple of `Float64` values of longitude and latitude.
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**Example**
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``` sql
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SELECT geohashDecode('ezs42') AS res;
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```
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``` text
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┌─res─────────────────────────────┐
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│ (-5.60302734375,42.60498046875) │
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└─────────────────────────────────┘
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```
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## geohashesInBox
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Returns an array of [geohash](#geohash)-encoded strings of given precision that fall inside and intersect boundaries of given box, basically a 2D grid flattened into array.
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**Syntax**
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``` sql
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geohashesInBox(longitude_min, latitude_min, longitude_max, latitude_max, precision)
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```
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**Arguments**
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- `longitude_min` — Minimum longitude. Range: `[-180°, 180°]`. Type: [Float](../../../sql-reference/data-types/float.md).
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- `latitude_min` — Minimum latitude. Range: `[-90°, 90°]`. Type: [Float](../../../sql-reference/data-types/float.md).
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- `longitude_max` — Maximum longitude. Range: `[-180°, 180°]`. Type: [Float](../../../sql-reference/data-types/float.md).
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- `latitude_max` — Maximum latitude. Range: `[-90°, 90°]`. Type: [Float](../../../sql-reference/data-types/float.md).
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- `precision` — Geohash precision. Range: `[1, 12]`. Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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:::note
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All coordinate parameters must be of the same type: either `Float32` or `Float64`.
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:::
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**Returned values**
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- Array of precision-long strings of geohash-boxes covering provided area, you should not rely on order of items.
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- `[]` - Empty array if minimum latitude and longitude values aren’t less than corresponding maximum values.
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Type: [Array](../../../sql-reference/data-types/array.md)([String](../../../sql-reference/data-types/string.md)).
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:::note
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Function throws an exception if resulting array is over 10’000’000 items long.
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:::
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**Example**
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Query:
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``` sql
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SELECT geohashesInBox(24.48, 40.56, 24.785, 40.81, 4) AS thasos;
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```
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Result:
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``` text
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┌─thasos──────────────────────────────────────┐
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│ ['sx1q','sx1r','sx32','sx1w','sx1x','sx38'] │
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└─────────────────────────────────────────────┘
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```
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[Original article](https://clickhouse.com/docs/en/sql-reference/functions/geo/geohash) <!--hide-->
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