ST_BUFFER

Introduced or updated: v1.2.911

Returns a GEOMETRY representing all points whose distance from the input geometry is less than or equal to the specified distance. The result is a MultiPolygon or NULL.

Syntax

ST_BUFFER(<geometry>, <distance>)

Arguments

Arguments	Description
<geometry>	A GEOMETRY expression. GeometryCollection is not supported.
<distance>	Buffer distance. Units match the coordinate system of the input geometry.

note

• For Point, MultiPoint, LineString, and MultiLineString: the absolute value of distance is used (negative behaves the same as positive).
• For Polygon and MultiPolygon: positive distance inflates, negative distance deflates.
• Returns NULL when the result is empty (e.g., zero distance on a Point, or deflating a polygon past zero area).
• For Polygon with distance 0: returns the polygon wrapped as a MultiPolygon.
• SRID is preserved in the output.

Return Type

Geometry (nullable).

Examples

-- Buffer a point (produces a polygon approximating a circle)
SELECT ST_BUFFER(TO_GEOMETRY('POINT(0 0)'), 1) IS NOT NULL;

┌────────┐
│ result │
├────────┤
│ true   │
└────────┘

-- Zero distance on a polygon returns itself as MultiPolygon
SELECT ST_ASWKT(
  ST_BUFFER(TO_GEOMETRY('POLYGON((0 0, 4 0, 4 4, 0 4, 0 0))'), 0)
);

┌─────────────────────────────────────────────────┐
│                     result                      │
├─────────────────────────────────────────────────┤
│ MULTIPOLYGON(((0 0,4 0,4 4,0 4,0 0)))          │
└─────────────────────────────────────────────────┘

-- Zero distance on a point returns NULL
SELECT ST_ASWKT(ST_BUFFER(TO_GEOMETRY('POINT(0 0)'), 0));

┌────────┐
│ result │
├────────┤
│ NULL   │
└────────┘

-- SRID is preserved
SELECT ST_SRID(ST_BUFFER(ST_GEOMETRYFROMWKT('POINT(0 0)', 4326), 1));

┌────────┐
│ result │
├────────┤
│ 4326   │
└────────┘