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Merge pull request #28669 from bharatnc/ncb/s2-function-docs
Add initial docs for s2 functions
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Nikita Mikhaylov
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docs/en/sql-reference/functions/geo/s2.md
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386
docs/en/sql-reference/functions/geo/s2.md
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---
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toc_title: S2 Geometry
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---
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# Functions for Working with S2 Index {#s2Index}
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[S2](https://s2geometry.io/) is a geographical indexing system where all geographical data is represented on a three-dimensional sphere (similar to a globe).
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In the S2 library points are represented as unit length vectors called S2 point indices (points on the surface of a three dimensional unit sphere) as opposed to traditional (latitude, longitude) pairs.
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## geoToS2 {#geoToS2}
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Returns [S2](#s2index) point index corresponding to the provided coordinates `(longitude, latitude)`.
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**Syntax**
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``` sql
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geoToS2(lon, lat)
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```
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**Arguments**
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- `lon` — Longitude. [Float64](../../../sql-reference/data-types/float.md).
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- `lat` — Latitude. [Float64](../../../sql-reference/data-types/float.md).
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**Returned values**
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- S2 point index.
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Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT geoToS2(37.79506683, 55.71290588) as s2Index;
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```
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Result:
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``` text
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┌─────────────s2Index─┐
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│ 4704772434919038107 │
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└─────────────────────┘
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```
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## s2ToGeo {#s2ToGeo}
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Returns geo coordinates `(longitude, latitude)` corresponding to the provided [S2](#s2index) point index.
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**Syntax**
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``` sql
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s2ToGeo(s2index)
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```
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**Arguments**
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- `s2Index` — S2 Index. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- A tuple consisting of two values: `tuple(lon,lat)`.
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Type: `lon` - [Float64](../../../sql-reference/data-types/float.md). `lat` — [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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SELECT s2ToGeo(4704772434919038107) as s2Coodrinates;
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```
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Result:
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``` text
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┌─s2Coodrinates────────────────────────┐
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│ (37.79506681471008,55.7129059052841) │
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└──────────────────────────────────────┘
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```
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## s2GetNeighbors {#s2GetNeighbors}
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Returns S2 neighbor indices corresponding to the provided [S2](#s2index)). Each cell in the S2 system is a quadrilateral bounded by four geodesics. So, each cell has 4 neighbors.
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**Syntax**
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``` sql
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s2GetNeighbors(s2index)
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```
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**Arguments**
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- `s2index` — S2 Index. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- An array consisting of the 4 neighbor indices: `array[s2index1, s2index3, s2index2, s2index4]`.
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Type: Each S2 index is [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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select s2GetNeighbors(5074766849661468672) AS s2Neighbors;
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```
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Result:
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``` text
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┌─s2Neighbors───────────────────────────────────────────────────────────────────────┐
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│ [5074766987100422144,5074766712222515200,5074767536856236032,5074767261978329088] │
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└───────────────────────────────────────────────────────────────────────────────────┘
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```
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## s2CellsIntersect {#s2CellsIntersect}
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Determines if the two provided [S2](#s2index)) cell indices intersect or not.
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**Syntax**
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``` sql
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s2CellsIntersect(s2index1, s2index2)
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```
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**Arguments**
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- `siIndex1`, `s2index2` — S2 Index. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- 1 — If the S2 cell indices intersect.
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- 0 — If the S2 cell indices don't intersect.
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Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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select s2CellsIntersect(9926595209846587392, 9926594385212866560) as intersect;
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```
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Result:
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``` text
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┌─intersect─┐
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│ 1 │
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└───────────┘
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```
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## s2CapContains {#s2CapContains}
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A cap represents a portion of the sphere that has been cut off by a plane. It is defined by a point on a sphere and a radius in degrees.
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Determines if a cap contains a s2 point index.
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**Syntax**
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``` sql
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s2CapContains(center, degrees, point)
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```
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**Arguments**
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- `center` - S2 point index corresponding to the cap. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `degrees` - Radius of the cap in degrees. [Float64](../../../sql-reference/data-types/float.md).
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- `point` - S2 point index. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- 1 — If the cap contains the S2 point index.
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- 0 — If the cap doesn't contain the S2 point index.
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Type: [UInt8](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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select s2CapContains(1157339245694594829, 1.0, 1157347770437378819) as capContains;
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```
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Result:
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``` text
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┌─capContains─┐
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│ 1 │
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└─────────────┘
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```
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## s2CapUnion {#s2CapUnion}
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A cap represents a portion of the sphere that has been cut off by a plane. It is defined by a point on a sphere and a radius in degrees.
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Determines the smallest cap that contains the given two input caps.
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**Syntax**
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``` sql
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s2CapUnion(center1, radius1, center2, radius2)
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```
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**Arguments**
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- `center1`, `center2` - S2 point indices corresponding to the two input caps. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `radius1`, `radius2` - Radii of the two input caps in degrees. [Float64](../../../sql-reference/data-types/float.md).
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**Returned values**
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- `center` - S2 point index corresponding the center of the smallest cap containing the two input caps. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `radius` - Radius of the smallest cap containing the two input caps. Type: [Float64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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SELECT s2CapUnion(3814912406305146967, 1.0, 1157347770437378819, 1.0) AS capUnion;
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```
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Result:
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``` text
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┌─capUnion───────────────────────────────┐
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│ (4534655147792050737,60.2088283994957) │
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└────────────────────────────────────────┘
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```
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## s2RectAdd{#s2RectAdd}
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In the S2 system, a rectangle is represented by a type of S2Region called a S2LatLngRect that represents a rectangle in latitude-longitude space.
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Increases the size of the bounding rectangle to include the given S2 point index.
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**Syntax**
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``` sql
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s2RectAdd(s2pointLow, s2pointHigh, s2Point)
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```
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**Arguments**
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- `s2PointLow` - Low S2 point index corresponding to the rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2PointHigh` - High S2 point index corresponding to the rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2Point` - Target S2 point index that the bound rectangle should be grown to include. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- `s2PointLow` - Low S2 cell id corresponding to the grown rectangle. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2PointHigh` - Hight S2 cell id corresponding to the grown rectangle. Type: [UInt64](../../../sql-reference/data-types/float.md).
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**Example**
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Query:
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``` sql
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SELECT s2RectAdd(5178914411069187297, 5177056748191934217, 5179056748191934217) as rectAdd;
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```
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Result:
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``` text
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┌─rectAdd───────────────────────────────────┐
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│ (5179062030687166815,5177056748191934217) │
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└───────────────────────────────────────────┘
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```
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## s2RectContains{#s2RectContains}
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In the S2 system, a rectangle is represented by a type of S2Region called a S2LatLngRect that represents a rectangle in latitude-longitude space.
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Determines if a given rectangle contains a S2 point index.
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**Syntax**
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``` sql
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s2RectContains(s2PointLow, s2PointHi, s2Point)
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```
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**Arguments**
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- `s2PointLow` - Low S2 point index corresponding to the rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2PointHigh` - High S2 point index corresponding to the rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2Point` - Target S2 point index. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- 1 — If the rectangle contains the given S2 point.
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- 0 — If the rectangle doesn't contain the given S2 point.
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**Example**
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Query:
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``` sql
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SELECT s2RectContains(5179062030687166815, 5177056748191934217, 5177914411069187297) AS rectContains
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```
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Result:
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``` text
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┌─rectContains─┐
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│ 0 │
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└──────────────┘
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```
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## s2RectUinion{#s2RectUnion}
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In the S2 system, a rectangle is represented by a type of S2Region called a S2LatLngRect that represents a rectangle in latitude-longitude space.
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Returns the smallest rectangle containing the union of this rectangle and the given rectangle.
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**Syntax**
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``` sql
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s2RectUnion(s2Rect1PointLow, s2Rect1PointHi, s2Rect2PointLow, s2Rect2PointHi)
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```
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**Arguments**
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- `s2Rect1PointLow`, `s2Rect1PointHi` - Low and High S2 point indices corresponding to the first rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2Rect2PointLow`, `s2Rect2PointHi` - Low and High S2 point indices corresponding to the second rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- `s2UnionRect2PointLow` - Low S2 cell id corresponding to the union rectangle. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2UnionRect2PointHi` - High S2 cell id corresponding to the union rectangle. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT s2RectUnion(5178914411069187297, 5177056748191934217, 5179062030687166815, 5177056748191934217) AS rectUnion
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```
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Result:
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``` text
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┌─rectUnion─────────────────────────────────┐
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│ (5179062030687166815,5177056748191934217) │
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└───────────────────────────────────────────┘
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```
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## s2RectIntersection{#s2RectIntersection}
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Returns the smallest Rectangle containing the intersection of this rectangle and the given rectangle.
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**Syntax**
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``` sql
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s2RectIntersection(s2Rect1PointLow, s2Rect1PointHi, s2Rect2PointLow, s2Rect2PointHi)
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```
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**Arguments**
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- `s2Rect1PointLow`, `s2Rect1PointHi` - Low and High S2 point indices corresponding to the first rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2Rect2PointLow`, `s2Rect2PointHi` - Low and High S2 point indices corresponding to the second rectangle. [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Returned values**
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- `s2UnionRect2PointLow` - Low S2 cell id corresponding to the rectangle containing the intersection of the given rectangles. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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- `s2UnionRect2PointHi` - Hi S2 cell id corresponding to the rectangle containing the intersection of the given rectangles. Type: [UInt64](../../../sql-reference/data-types/int-uint.md).
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**Example**
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Query:
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``` sql
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SELECT s2RectIntersection(5178914411069187297, 5177056748191934217, 5179062030687166815, 5177056748191934217) AS rectIntersection
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```
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Result:
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``` text
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┌─rectIntersection──────────────────────────┐
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│ (5178914411069187297,5177056748191934217) │
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└───────────────────────────────────────────┘
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```
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