| PostgreSQL 7.4.30 Documentation | ||||
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Geometric data types represent two-dimensional spatial objects. Table 8-16 shows the geometric types available in PostgreSQL. The most fundamental type, the point, forms the basis for all of the other types.
Table 8-16. Geometric Types
| Name | Storage Size | Representation | Description |
|---|---|---|---|
| point | 16 bytes | Point on the plane | (x,y) |
| line | 32 bytes | Infinite line (not fully implemented) | ((x1,y1),(x2,y2)) |
| lseg | 32 bytes | Finite line segment | ((x1,y1),(x2,y2)) |
| box | 32 bytes | Rectangular box | ((x1,y1),(x2,y2)) |
| path | 16+16n bytes | Closed path (similar to polygon) | ((x1,y1),...) |
| path | 16+16n bytes | Open path | [(x1,y1),...] |
| polygon | 40+16n bytes | Polygon (similar to closed path) | ((x1,y1),...) |
| circle | 24 bytes | Circle | <(x,y),r> (center and radius) |
A rich set of functions and operators is available to perform various geometric operations such as scaling, translation, rotation, and determining intersections. They are explained in Section 9.9.
Points are the fundamental two-dimensional building block for geometric types. Values of type point are specified using either of the following syntaxes:
( x , y ) x , y
where x and y are the respective coordinates as floating-point numbers.
Points are output using the first syntax.
Line segments (lseg) are represented by pairs of points. Values of type lseg are specified using any of the following syntaxes:
[ ( x1 , y1 ) , ( x2 , y2 ) ]
( ( x1 , y1 ) , ( x2 , y2 ) )
( x1 , y1 ) , ( x2 , y2 )
x1 , y1 , x2 , y2
where (x1,y1) and (x2,y2) are the end points of the line segment.
Line segments are output using the first syntax.
Boxes are represented by pairs of points that are opposite corners of the box. Values of type box are specified using any of the following syntaxes:
( ( x1 , y1 ) , ( x2 , y2 ) )
( x1 , y1 ) , ( x2 , y2 )
x1 , y1 , x2 , y2
where (x1,y1) and (x2,y2) are the opposite corners of the box.
Boxes are output using the second syntax.
Any two opposite corners can be supplied on input, but the values will be reordered as needed to store the upper right and lower left corners, in that order.
Paths are represented by connected sets of points. Paths can
be open, where the first and last
points in the set are not connected, and closed, where the first and last point are
connected. The functions popen(p) and
pclose(p) are supplied to force a path to
be open or closed, and the functions isopen(p) and
isclosed(p) are supplied to test for either
type in an expression.
Values of type path are specified using any of the following syntaxes:
[ ( x1 , y1 ) , ... , ( xn , yn ) ]
( ( x1 , y1 ) , ... , ( xn , yn ) )
( x1 , y1 ) , ... , ( xn , yn )
( x1 , y1 , ... , xn , yn )
x1 , y1 , ... , xn , yn
where the points are the end points of the line segments comprising the path. Square brackets ([]) indicate an open path, while parentheses (()) indicate a closed path. When the outermost parentheses are omitted, as in the third through fifth syntaxes, a closed path is assumed.
Paths are output using the first syntax.
Polygons are represented by sets of points. Polygons should probably be considered equivalent to closed paths, but are stored differently and have their own set of support routines.
Values of type polygon are specified using any of the following syntaxes:
( ( x1 , y1 ) , ... , ( xn , yn ) )
( x1 , y1 ) , ... , ( xn , yn )
( x1 , y1 , ... , xn , yn )
x1 , y1 , ... , xn , yn
where the points are the end points of the line segments comprising the boundary of the polygon.
Polygons are output using the first syntax.
Circles are represented by a center point and a radius. Values of type circle are specified using any of the following syntaxes:
< ( x , y ) , r >
( ( x , y ) , r )
( x , y ) , r
x , y , r
where (x,y) is the center and r is the radius of the circle.
Circles are output using the first syntax.