Class PolygonFunction

All Implemented Interfaces:
ADQLObject, ADQLOperand

public class PolygonFunction extends GeometryFunction
It represents the POLYGON function of the ADQL language.

This function expresses a region on the sky with boundaries denoted by great circles passing through specified vertices. It corresponds semantically to the STC Polygon.

A polygon is described by a list of vertices in a single coordinate system, with each vertex connected to the next along a great circle and the last vertex implicitly connected to the first vertex.

The function arguments specify three or more vertices, where:

  • the position of the vertices are given as a sequence of numeric coordinates in degrees, or as a sequence of geometric POINTs
  • the numeric coordinates MUST be within the ranges [0,360] and [-90,90]

Example:

A function expressing a triangle, whose vertices are (10.0, -10.5), (20.0, 20.5) and (30.0,30.5) in degrees would be written as follows:

POLYGON(10.0, -10.5, 20.0, 20.5, 30.0, 30.5)

, where all numeric values are in degrees.

or alternatively as follows:

POLYGON(POINT(10.0, -10.5), POINT(20.0, 20.5), POINT(30.0, 30.5))

The coordinates for the POLYGON vertices may be literal values, as above, or they may be column references, functions or expressions that return numeric values.

Example:

POLYGON(t1.ra, t1.dec + 5, t1.ra - 5, t1.dec - 5, t1.ra - 5, t1.dec + 5)

, where t1.ra and t1.dec are references to database columns that contain numeric values.

Alternatively, the coordinates for the POLYGON vertices may be column references, functions or expressions that return POINT values.

Example:

POLYGON(t2.toppoint, t2.bottomleft, t2.bottomright)

, where t2.toppoint, t2.bottomleft and t2.bottomright are references to database columns that contain POINT values.

The coordinates for the vertices MUST all be expressed in the same datatype. The POLYGON function does not support a mixture of numeric and POINT arguments.

For historical reasons, the POLYGON function accepts an optional string value as the first argument. As of this version of the specification (2.1) this parameter has been marked as deprecated. Future versions of this specification (> 2.1) may remove this parameter.

  • Field Details

    • FEATURE

      public static final LanguageFeature FEATURE
      Description of this ADQL Feature.
      Since:
      2.0
    • coordinates

      protected Vector<ADQLOperand> coordinates
      The vertices.
  • Constructor Details

  • Method Details

    • getFeatureDescription

      public final LanguageFeature getFeatureDescription()
      Description copied from interface: ADQLObject
      Get the description of this ADQL's Language Feature.

      Note: Getting this description is generally only useful when discovery optional features so that determining if they are allowed to be used in ADQL queries.

      Returns:
      Description of this ADQL object as an ADQL's feature.
    • getCopy

      public ADQLObject getCopy() throws Exception
      Description copied from interface: ADQLObject
      Gets a (deep) copy of this ADQL object.
      Returns:
      The copy of this ADQL object.
      Throws:
      Exception - If there is any error during the copy.
    • getName

      public String getName()
      Description copied from interface: ADQLObject
      Gets the name of this object in ADQL.
      Returns:
      The name of this ADQL object.
    • isNumeric

      public boolean isNumeric()
      Description copied from interface: ADQLOperand
      Tell whether this operand is numeric or not.
      Returns:
      true if this operand is numeric, false otherwise.
    • isString

      public boolean isString()
      Description copied from interface: ADQLOperand
      Tell whether this operand is a string or not.
      Returns:
      true if this operand is a string, false otherwise.
    • isGeometry

      public boolean isGeometry()
      Description copied from interface: ADQLOperand
      Tell whether this operand is a geometrical region or not.
      Returns:
      true if this operand is a geometry, false otherwise.
    • getParameters

      public ADQLOperand[] getParameters()
      Description copied from class: ADQLFunction
      Gets the list of all parameters of this function.
      Specified by:
      getParameters in class ADQLFunction
      Returns:
      Its parameters list.
    • getNbParameters

      public int getNbParameters()
      Description copied from class: ADQLFunction
      Gets the number of parameters this function has.
      Specified by:
      getNbParameters in class ADQLFunction
      Returns:
      Number of parameters.
    • getParameter

      public ADQLOperand getParameter(int index) throws ArrayIndexOutOfBoundsException
      Description copied from class: ADQLFunction
      Gets the index-th parameter.
      Specified by:
      getParameter in class ADQLFunction
      Parameters:
      index - Parameter number.
      Returns:
      The corresponding parameter.
      Throws:
      ArrayIndexOutOfBoundsException - If the index is incorrect (index < 0 || index >= getNbParameters()).
    • setParameter

      public ADQLOperand setParameter(int index, ADQLOperand replacer) throws ArrayIndexOutOfBoundsException, NullPointerException, Exception
      Description copied from class: ADQLFunction
      Replaces the index-th parameter by the given one.
      Specified by:
      setParameter in class ADQLFunction
      Parameters:
      index - Index of the parameter to replace.
      replacer - The replacer.
      Returns:
      The replaced parameter.
      Throws:
      ArrayIndexOutOfBoundsException - If the index is incorrect (index < 0 || index >= getNbParameters()).
      NullPointerException - If a required parameter must be replaced by a NULL object.
      Exception - If another error occurs.