mirror of
https://github.com/ClickHouse/ClickHouse.git
synced 2024-11-12 02:23:14 +00:00
113 lines
4.0 KiB
Markdown
113 lines
4.0 KiB
Markdown
---
|
||
toc_title: Geohash
|
||
---
|
||
|
||
# Functions for Working with Geohash {#geohash}
|
||
|
||
[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.
|
||
|
||
If you need to manually convert geographic coordinates to geohash strings, you can use [geohash.org](http://geohash.org/).
|
||
|
||
## geohashEncode {#geohashencode}
|
||
|
||
Encodes latitude and longitude as a [geohash](#geohash)-string.
|
||
|
||
``` sql
|
||
geohashEncode(longitude, latitude, [precision])
|
||
```
|
||
|
||
**Input values**
|
||
|
||
- longitude - longitude part of the coordinate you want to encode. Floating in range`[-180°, 180°]`
|
||
- latitude - latitude part of the coordinate you want to encode. Floating in range `[-90°, 90°]`
|
||
- 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`.
|
||
|
||
**Returned values**
|
||
|
||
- alphanumeric `String` of encoded coordinate (modified version of the base32-encoding alphabet is used).
|
||
|
||
**Example**
|
||
|
||
``` sql
|
||
SELECT geohashEncode(-5.60302734375, 42.593994140625, 0) AS res;
|
||
```
|
||
|
||
``` text
|
||
┌─res──────────┐
|
||
│ ezs42d000000 │
|
||
└──────────────┘
|
||
```
|
||
|
||
## geohashDecode {#geohashdecode}
|
||
|
||
Decodes any [geohash](#geohash)-encoded string into longitude and latitude.
|
||
|
||
**Input values**
|
||
|
||
- encoded string - geohash-encoded string.
|
||
|
||
**Returned values**
|
||
|
||
- (longitude, latitude) - 2-tuple of `Float64` values of longitude and latitude.
|
||
|
||
**Example**
|
||
|
||
``` sql
|
||
SELECT geohashDecode('ezs42') AS res;
|
||
```
|
||
|
||
``` text
|
||
┌─res─────────────────────────────┐
|
||
│ (-5.60302734375,42.60498046875) │
|
||
└─────────────────────────────────┘
|
||
```
|
||
|
||
## geohashesInBox {#geohashesinbox}
|
||
|
||
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.
|
||
|
||
**Syntax**
|
||
|
||
``` sql
|
||
geohashesInBox(longitude_min, latitude_min, longitude_max, latitude_max, precision)
|
||
```
|
||
|
||
**Arguments**
|
||
|
||
- `longitude_min` — Minimum longitude. Range: `[-180°, 180°]`. Type: [Float](../../../sql-reference/data-types/float.md).
|
||
- `latitude_min` — Minimum latitude. Range: `[-90°, 90°]`. Type: [Float](../../../sql-reference/data-types/float.md).
|
||
- `longitude_max` — Maximum longitude. Range: `[-180°, 180°]`. Type: [Float](../../../sql-reference/data-types/float.md).
|
||
- `latitude_max` — Maximum latitude. Range: `[-90°, 90°]`. Type: [Float](../../../sql-reference/data-types/float.md).
|
||
- `precision` — Geohash precision. Range: `[1, 12]`. Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
|
||
|
||
!!! info "Note"
|
||
All coordinate parameters must be of the same type: either `Float32` or `Float64`.
|
||
|
||
**Returned values**
|
||
|
||
- Array of precision-long strings of geohash-boxes covering provided area, you should not rely on order of items.
|
||
- `[]` - Empty array if minimum latitude and longitude values aren’t less than corresponding maximum values.
|
||
|
||
Type: [Array](../../../sql-reference/data-types/array.md)([String](../../../sql-reference/data-types/string.md)).
|
||
|
||
!!! info "Note"
|
||
Function throws an exception if resulting array is over 10’000’000 items long.
|
||
|
||
**Example**
|
||
|
||
Query:
|
||
|
||
``` sql
|
||
SELECT geohashesInBox(24.48, 40.56, 24.785, 40.81, 4) AS thasos;
|
||
```
|
||
|
||
Result:
|
||
|
||
``` text
|
||
┌─thasos──────────────────────────────────────┐
|
||
│ ['sx1q','sx1r','sx32','sx1w','sx1x','sx38'] │
|
||
└─────────────────────────────────────────────┘
|
||
```
|
||
|
||
[Original article](https://clickhouse.com/docs/en/sql-reference/functions/geo/geohash) <!--hide-->
|