mirror of
https://git.osgeo.org/gitea/postgis/postgis
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74 lines
2.2 KiB
XML
74 lines
2.2 KiB
XML
<?xml version="1.0" encoding="UTF-8"?>
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<refentry id="ST_IsRing">
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<refnamediv>
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<refname>ST_IsRing</refname>
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<refpurpose>Returns <varname>TRUE</varname> if this
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<varname>LINESTRING</varname> is both closed and simple.</refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>boolean <function>ST_IsRing</function></funcdef>
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<paramdef><type>geometry </type> <parameter>g</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsection>
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<title>Description</title>
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<para>Returns <varname>TRUE</varname> if this
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<varname>LINESTRING</varname> is both <xref linkend="ST_IsClosed" />
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(<function>ST_StartPoint(<parameter>g</parameter>)</function>
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<function>~=</function>
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<function>ST_Endpoint(<parameter>g</parameter>)</function>) and <xref
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linkend="ST_IsSimple" /> (does not self intersect).</para>
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<para><inlinemediaobject>
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<imageobject>
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<imagedata fileref="images/check.png" />
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</imageobject>
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</inlinemediaobject> This method implements the <ulink
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url="http://www.opengeospatial.org/standards/sfs">OpenGIS Simple Features
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Implementation Specification for SQL.</ulink> OGC SFSQL 1.1 -
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2.1.5.1</para>
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<para><inlinemediaobject>
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<imageobject>
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<imagedata fileref="images/check.png" />
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</imageobject>
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</inlinemediaobject> This method implements the SQL/MM specification:
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SQL-MM 3: 7.1.6</para>
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<note>
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<para>SQL-MM defines the result of
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<function>ST_IsRing(<varname>NULL</varname>)</function> to be 0, while
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PostGIS returns <varname>NULL</varname>.</para>
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</note>
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<!-- Optionally mention 3d support -->
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<para><inlinemediaobject>
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<imageobject>
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<imagedata fileref="images/check.png" />
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</imageobject>
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</inlinemediaobject> This function supports 3d and will not drop the z-index.</para>
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</refsection>
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<refsection>
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<title>Examples</title>
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<programlisting>
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</programlisting>
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</refsection>
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<refsection>
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<title>See Also</title>
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<para><xref linkend="ST_IsSimple" />, <xref linkend="ST_StartPoint" />,
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<xref linkend="ST_EndPoint" /></para>
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</refsection>
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</refentry> |