The geometric types point
, box
, lseg
, line
, path
, polygon
, and circle
have a large set of native support functions and operators, shown in Table 9-33, Table 9-34, and Table 9-35.
Caution: Note that the "same as" operator,
~=
, represents the usual notion of equality for thepoint
,box
,polygon
, andcircle
types. Some of these types also have an=
operator, but=
compares for equal areas only. The other scalar comparison operators (<=
and so on) likewise compare areas for these types.
Table 9-33. Geometric Operators
Operator | Description | Example |
---|---|---|
+ | Translation | box '((0,0),(1,1))' + point '(2.0,0)' |
- | Translation | box '((0,0),(1,1))' - point '(2.0,0)' |
* | Scaling/rotation | box '((0,0),(1,1))' * point '(2.0,0)' |
/ | Scaling/rotation | box '((0,0),(2,2))' / point '(2.0,0)' |
# | Point or box of intersection | box '((1,-1),(-1,1))' # box '((1,1),(-2,-2))' |
# | Number of points in path or polygon | # path '((1,0),(0,1),(-1,0))' |
@-@ | Length or circumference | @-@ path '((0,0),(1,0))' |
@@ | Center | @@ circle '((0,0),10)' |
## | Closest point to first operand on second operand | point '(0,0)' ## lseg '((2,0),(0,2))' |
<-> | Distance between | circle '((0,0),1)' <-> circle '((5,0),1)' |
&& | Overlaps? (One point in common makes this true.) | box '((0,0),(1,1))' && box '((0,0),(2,2))' |
<< | Is strictly left of? | circle '((0,0),1)' << circle '((5,0),1)' |
>> | Is strictly right of? | circle '((5,0),1)' >> circle '((0,0),1)' |
&< | Does not extend to the right of? | box '((0,0),(1,1))' &< box '((0,0),(2,2))' |
&> | Does not extend to the left of? | box '((0,0),(3,3))' &> box '((0,0),(2,2))' |
<<| | Is strictly below? | box '((0,0),(3,3))' <<| box '((3,4),(5,5))' |
|>> | Is strictly above? | box '((3,4),(5,5))' |>> box '((0,0),(3,3))' |
&<| | Does not extend above? | box '((0,0),(1,1))' &<| box '((0,0),(2,2))' |
|&> | Does not extend below? | box '((0,0),(3,3))' |&> box '((0,0),(2,2))' |
<^ | Is below (allows touching)? | circle '((0,0),1)' <^ circle '((0,5),1)' |
>^ | Is above (allows touching)? | circle '((0,5),1)' >^ circle '((0,0),1)' |
?# | Intersects? | lseg '((-1,0),(1,0))' ?# box '((-2,-2),(2,2))' |
?- | Is horizontal? | ?- lseg '((-1,0),(1,0))' |
?- | Are horizontally aligned? | point '(1,0)' ?- point '(0,0)' |
?| | Is vertical? | ?| lseg '((-1,0),(1,0))' |
?| | Are vertically aligned? | point '(0,1)' ?| point '(0,0)' |
?-| | Is perpendicular? | lseg '((0,0),(0,1))' ?-| lseg '((0,0),(1,0))' |
?|| | Are parallel? | lseg '((-1,0),(1,0))' ?|| lseg '((-1,2),(1,2))' |
@> | Contains? | circle '((0,0),2)' @> point '(1,1)' |
<@ | Contained in or on? | point '(1,1)' <@ circle '((0,0),2)' |
~= | Same as? | polygon '((0,0),(1,1))' ~= polygon '((1,1),(0,0))' |
Note: Before PostgreSQL 8.2, the containment operators
@>
and<@
were respectively called~
and@
. These names are still available, but are deprecated and will eventually be removed.
Table 9-34. Geometric Functions
Function | Return Type | Description | Example |
---|---|---|---|
area( | double precision | area | area(box '((0,0),(1,1))') |
center( | point | center | center(box '((0,0),(1,2))') |
diameter( | double precision | diameter of circle | diameter(circle '((0,0),2.0)') |
height( | double precision | vertical size of box | height(box '((0,0),(1,1))') |
isclosed( | boolean | a closed path? | isclosed(path '((0,0),(1,1),(2,0))') |
isopen( | boolean | an open path? | isopen(path '[(0,0),(1,1),(2,0)]') |
length( | double precision | length | length(path '((-1,0),(1,0))') |
npoints( | int | number of points | npoints(path '[(0,0),(1,1),(2,0)]') |
npoints( | int | number of points | npoints(polygon '((1,1),(0,0))') |
pclose( | path | convert path to closed | pclose(path '[(0,0),(1,1),(2,0)]') |
popen( | path | convert path to open | popen(path '((0,0),(1,1),(2,0))') |
radius( | double precision | radius of circle | radius(circle '((0,0),2.0)') |
width( | double precision | horizontal size of box | width(box '((0,0),(1,1))') |
Table 9-35. Geometric Type Conversion Functions
Function | Return Type | Description | Example |
---|---|---|---|
box( | box | circle to box | box(circle '((0,0),2.0)') |
box( | box | point to empty box | box(point '(0,0)') |
box( | box | points to box | box(point '(0,0)', point '(1,1)') |
box( | box | polygon to box | box(polygon '((0,0),(1,1),(2,0))') |
bound_box( | box | boxes to bounding box | bound_box(box '((0,0),(1,1))', box '((3,3),(4,4))') |
circle( | circle | box to circle | circle(box '((0,0),(1,1))') |
circle( | circle | center and radius to circle | circle(point '(0,0)', 2.0) |
circle( | circle | polygon to circle | circle(polygon '((0,0),(1,1),(2,0))') |
line( | line | points to line | line(point '(-1,0)', point '(1,0)') |
lseg( | lseg | box diagonal to line segment | lseg(box '((-1,0),(1,0))') |
lseg( | lseg | points to line segment | lseg(point '(-1,0)', point '(1,0)') |
path( | path | polygon to path | path(polygon '((0,0),(1,1),(2,0))') |
point( | point | construct point | point(23.4, -44.5) |
point( | point | center of box | point(box '((-1,0),(1,0))') |
point( | point | center of circle | point(circle '((0,0),2.0)') |
point( | point | center of line segment | point(lseg '((-1,0),(1,0))') |
point( | point | center of polygon | point(polygon '((0,0),(1,1),(2,0))') |
polygon( | polygon | box to 4-point polygon | polygon(box '((0,0),(1,1))') |
polygon( | polygon | circle to 12-point polygon | polygon(circle '((0,0),2.0)') |
polygon( | polygon | circle to npts -point polygon | polygon(12, circle '((0,0),2.0)') |
polygon( | polygon | path to polygon | polygon(path '((0,0),(1,1),(2,0))') |
It is possible to access the two component numbers of a point
as though the point were an array with indexes 0 and 1. For example, if t.p
is a point
column then SELECT p[0] FROM t
retrieves the X coordinate and UPDATE t SET p[1] = ...
changes the Y coordinate. In the same way, a value of type box
or lseg
can be treated as an array of two point
values.
The area
function works for the types box
, circle
, and path
. The area
function only works on the path
data type if the points in the path
are non-intersecting. For example, the path
'((0,0),(0,1),(2,1),(2,2),(1,2),(1,0),(0,0))'::PATH
will not work; however, the following visually identical path
'((0,0),(0,1),(1,1),(1,2),(2,2),(2,1),(1,1),(1,0),(0,0))'::PATH
will work. If the concept of an intersecting versus non-intersecting path
is confusing, draw both of the above path
s side by side on a piece of graph paper.
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