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PostgreSQL 7.4.30 Documentation | ||||
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Prev | Fast Backward | Chapter 8. Data Types | Fast Forward | Next |

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

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

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(`

and
`p`)`pclose(`

are supplied to force a path to
be open or closed, and the functions `p`)`isopen(`

and
`p`)`isclosed(`

are supplied to test for either
type in an expression.`p`)

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) ,rx,y,r

where `( x,y)`
is the center and

Circles are output using the first syntax.