TYPE happiness AS ENUM ('happy', 'very happy', 'ecstatic');
CREATE TABLE holidays (
    num_weeks integer,
    happiness happiness
);
INSERT INTO holidays(num_weeks,happiness) VALUES (4, 'happy');
INSERT INTO holidays(num_weeks,happiness) VALUES (6, 'very happy');
INSERT INTO holidays(num_weeks,happiness) VALUES (8, 'ecstatic');
INSERT INTO holidays(num_weeks,happiness) VALUES (2, 'sad');
ERROR:  invalid input value for enum happiness: "sad"
SELECT person.name, holidays.num_weeks FROM person, holidays
  WHERE person.current_mood = holidays.happiness;
ERROR:  operator does not exist: mood = happiness
</programlisting>
    </para>

    <para>
     If you really need to do something like that, you can either
     write a custom operator or add explicit casts to your query:

<programlisting>
SELECT person.name, holidays.num_weeks FROM person, holidays
  WHERE person.current_mood::text = holidays.happiness::text;
 name | num_weeks
------+-----------
 Moe  |         4
(1 row)

</programlisting>
    </para>
   </sect2>

   <sect2 id="datatype-enum-implementation-details">
    <title>Implementation Details</title>

    <para>
     Enum labels are case sensitive, so
     <type>'happy'</type> is not the same as <type>'HAPPY'</type>.
     White space in the labels is significant too.
    </para>

    <para>
     Although enum types are primarily intended for static sets of values,
     there is support for adding new values to an existing enum type, and for
     renaming values (see <xref linkend="sql-altertype"/>).  Existing values
     cannot be removed from an enum type, nor can the sort ordering of such
     values be changed, short of dropping and re-creating the enum type.
    </para>

    <para>
     An enum value occupies four bytes on disk.  The length of an enum
     value's textual label is limited by the <symbol>NAMEDATALEN</symbol>
     setting compiled into <productname>PostgreSQL</productname>; in standard
     builds this means at most 63 bytes.
    </para>

    <para>
     The translations from internal enum values to textual labels are
     kept in the system catalog
     <link linkend="catalog-pg-enum"><structname>pg_enum</structname></link>.
     Querying this catalog directly can be useful.
    </para>

   </sect2>
  </sect1>

  <sect1 id="datatype-geometric">
   <title>Geometric Types</title>

   <para>
    Geometric data types represent two-dimensional spatial
    objects. <xref linkend="datatype-geo-table"/> shows the geometric
    types available in <productname>PostgreSQL</productname>.
   </para>

    <table id="datatype-geo-table">
     <title>Geometric Types</title>
     <tgroup cols="4">
      <colspec colname="col1" colwidth="1*"/>
      <colspec colname="col2" colwidth="1*"/>
      <colspec colname="col3" colwidth="2*"/>
      <colspec colname="col4" colwidth="1*"/>
      <thead>
       <row>
        <entry>Name</entry>
        <entry>Storage Size</entry>
        <entry>Description</entry>
        <entry>Representation</entry>
       </row>
      </thead>
      <tbody>
       <row>
        <entry><type>point</type></entry>
        <entry>16 bytes</entry>
        <entry>Point on a plane</entry>
        <entry>(x,y)</entry>
       </row>
       <row>
        <entry><type>line</type></entry>
        <entry>24 bytes</entry>
        <entry>Infinite line</entry>
        <entry>{A,B,C}</entry>
       </row>
       <row>
        <entry><type>lseg</type></entry>
        <entry>32 bytes</entry>
        <entry>Finite line segment</entry>
        <entry>[(x1,y1),(x2,y2)]</entry>
       </row>
       <row>
        <entry><type>box</type></entry>
        <entry>32 bytes</entry>
        <entry>Rectangular box</entry>
        <entry>(x1,y1),(x2,y2)</entry>
       </row>
       <row>
        <entry><type>path</type></entry>
        <entry>16+16n bytes</entry>
        <entry>Closed path (similar to polygon)</entry>
        <entry>((x1,y1),...)</entry>
       </row>
       <row>
        <entry><type>path</type></entry>