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><DIV
CLASS="SECT1"
><H1
CLASS="SECT1"
><A
NAME="LTREE"
>F.21. ltree</A
></H1
><P
>  This module implements a data type <TT
CLASS="TYPE"
>ltree</TT
> for representing
  labels of data stored in a hierarchical tree-like structure.
  Extensive facilities for searching through label trees are provided.
 </P
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN149388"
>F.21.1. Definitions</A
></H2
><P
>   A <I
CLASS="FIRSTTERM"
>label</I
> is a sequence of alphanumeric characters
   and underscores (for example, in C locale the characters
   <TT
CLASS="LITERAL"
>A-Za-z0-9_</TT
> are allowed).  Labels must be less than 256 bytes
   long.
  </P
><P
>   Examples: <TT
CLASS="LITERAL"
>42</TT
>, <TT
CLASS="LITERAL"
>Personal_Services</TT
>
  </P
><P
>   A <I
CLASS="FIRSTTERM"
>label path</I
> is a sequence of zero or more
   labels separated by dots, for example <TT
CLASS="LITERAL"
>L1.L2.L3</TT
>, representing
   a path from the root of a hierarchical tree to a particular node.  The
   length of a label path must be less than 65Kb, but keeping it under 2Kb is
   preferable.  In practice this is not a major limitation; for example,
   the longest label path in the DMOZ catalogue (<A
HREF="http://www.dmoz.org"
TARGET="_top"
>http://www.dmoz.org</A
>) is about 240 bytes.
  </P
><P
>   Example: <TT
CLASS="LITERAL"
>Top.Countries.Europe.Russia</TT
>
  </P
><P
>   The <TT
CLASS="FILENAME"
>ltree</TT
> module provides several data types:
  </P
><P
></P
><UL
><LI
><P
>     <TT
CLASS="TYPE"
>ltree</TT
> stores a label path.
    </P
></LI
><LI
><P
>     <TT
CLASS="TYPE"
>lquery</TT
> represents a regular-expression-like pattern
     for matching <TT
CLASS="TYPE"
>ltree</TT
> values.  A simple word matches that
     label within a path.  A star symbol (<TT
CLASS="LITERAL"
>*</TT
>) matches zero
     or more labels.  For example:
</P><PRE
CLASS="SYNOPSIS"
>foo         <I
CLASS="LINEANNOTATION"
>Match the exact label path <TT
CLASS="LITERAL"
>foo</TT
></I
>
*.foo.*     <I
CLASS="LINEANNOTATION"
>Match any label path containing the label <TT
CLASS="LITERAL"
>foo</TT
></I
>
*.foo       <I
CLASS="LINEANNOTATION"
>Match any label path whose last label is <TT
CLASS="LITERAL"
>foo</TT
></I
></PRE
><P>
    </P
><P
>     Star symbols can also be quantified to restrict how many labels
     they can match:
</P><PRE
CLASS="SYNOPSIS"
>*{<TT
CLASS="REPLACEABLE"
><I
>n</I
></TT
>}        <I
CLASS="LINEANNOTATION"
>Match exactly <TT
CLASS="REPLACEABLE"
><I
>n</I
></TT
> labels</I
>
*{<TT
CLASS="REPLACEABLE"
><I
>n</I
></TT
>,}       <I
CLASS="LINEANNOTATION"
>Match at least <TT
CLASS="REPLACEABLE"
><I
>n</I
></TT
> labels</I
>
*{<TT
CLASS="REPLACEABLE"
><I
>n</I
></TT
>,<TT
CLASS="REPLACEABLE"
><I
>m</I
></TT
>}      <I
CLASS="LINEANNOTATION"
>Match at least <TT
CLASS="REPLACEABLE"
><I
>n</I
></TT
> but not more than <TT
CLASS="REPLACEABLE"
><I
>m</I
></TT
> labels</I
>
*{,<TT
CLASS="REPLACEABLE"
><I
>m</I
></TT
>}       <I
CLASS="LINEANNOTATION"
>Match at most <TT
CLASS="REPLACEABLE"
><I
>m</I
></TT
> labels &mdash; same as </I
> *{0,<TT
CLASS="REPLACEABLE"
><I
>m</I
></TT
>}</PRE
><P>
    </P
><P
>     There are several modifiers that can be put at the end of a non-star
     label in <TT
CLASS="TYPE"
>lquery</TT
> to make it match more than just the exact match:
</P><PRE
CLASS="SYNOPSIS"
>@           <I
CLASS="LINEANNOTATION"
>Match case-insensitively, for example <TT
CLASS="LITERAL"
>a@</TT
> matches <TT
CLASS="LITERAL"
>A</TT
></I
>
*           <I
CLASS="LINEANNOTATION"
>Match any label with this prefix, for example <TT
CLASS="LITERAL"
>foo*</TT
> matches <TT
CLASS="LITERAL"
>foobar</TT
></I
>
%           <I
CLASS="LINEANNOTATION"
>Match initial underscore-separated words</I
></PRE
><P>
     The behavior of <TT
CLASS="LITERAL"
>%</TT
> is a bit complicated.  It tries to match
     words rather than the entire label.  For example
     <TT
CLASS="LITERAL"
>foo_bar%</TT
> matches <TT
CLASS="LITERAL"
>foo_bar_baz</TT
> but not
     <TT
CLASS="LITERAL"
>foo_barbaz</TT
>.  If combined with <TT
CLASS="LITERAL"
>*</TT
>, prefix
     matching applies to each word separately, for example
     <TT
CLASS="LITERAL"
>foo_bar%*</TT
> matches <TT
CLASS="LITERAL"
>foo1_bar2_baz</TT
> but
     not <TT
CLASS="LITERAL"
>foo1_br2_baz</TT
>.
    </P
><P
>     Also, you can write several possibly-modified labels separated with
     <TT
CLASS="LITERAL"
>|</TT
> (OR) to match any of those labels, and you can put
     <TT
CLASS="LITERAL"
>!</TT
> (NOT) at the start to match any label that doesn't
     match any of the alternatives.
    </P
><P
>     Here's an annotated example of <TT
CLASS="TYPE"
>lquery</TT
>:
</P><PRE
CLASS="PROGRAMLISTING"
>Top.*{0,2}.sport*@.!football|tennis.Russ*|Spain
a.  b.     c.      d.               e.</PRE
><P>
     This query will match any label path that:
    </P
><P
></P
><OL
TYPE="a"
><LI
><P
>       begins with the label <TT
CLASS="LITERAL"
>Top</TT
>
      </P
></LI
><LI
><P
>       and next has zero to two labels before
      </P
></LI
><LI
><P
>       a label beginning with the case-insensitive prefix <TT
CLASS="LITERAL"
>sport</TT
>
      </P
></LI
><LI
><P
>       then a label not matching <TT
CLASS="LITERAL"
>football</TT
> nor
       <TT
CLASS="LITERAL"
>tennis</TT
>
      </P
></LI
><LI
><P
>       and then ends with a label beginning with <TT
CLASS="LITERAL"
>Russ</TT
> or
       exactly matching <TT
CLASS="LITERAL"
>Spain</TT
>.
      </P
></LI
></OL
></LI
><LI
><P
><TT
CLASS="TYPE"
>ltxtquery</TT
> represents a full-text-search-like
    pattern for matching <TT
CLASS="TYPE"
>ltree</TT
> values.  An
    <TT
CLASS="TYPE"
>ltxtquery</TT
> value contains words, possibly with the
    modifiers <TT
CLASS="LITERAL"
>@</TT
>, <TT
CLASS="LITERAL"
>*</TT
>, <TT
CLASS="LITERAL"
>%</TT
> at the end;
    the modifiers have the same meanings as in <TT
CLASS="TYPE"
>lquery</TT
>.
    Words can be combined with <TT
CLASS="LITERAL"
>&amp;</TT
> (AND),
    <TT
CLASS="LITERAL"
>|</TT
> (OR), <TT
CLASS="LITERAL"
>!</TT
> (NOT), and parentheses.
    The key difference from
    <TT
CLASS="TYPE"
>lquery</TT
> is that <TT
CLASS="TYPE"
>ltxtquery</TT
> matches words without
    regard to their position in the label path.
    </P
><P
>     Here's an example <TT
CLASS="TYPE"
>ltxtquery</TT
>:
</P><PRE
CLASS="PROGRAMLISTING"
>Europe &amp; Russia*@ &amp; !Transportation</PRE
><P>
     This will match paths that contain the label <TT
CLASS="LITERAL"
>Europe</TT
> and
     any label beginning with <TT
CLASS="LITERAL"
>Russia</TT
> (case-insensitive),
     but not paths containing the label <TT
CLASS="LITERAL"
>Transportation</TT
>.
     The location of these words within the path is not important.
     Also, when <TT
CLASS="LITERAL"
>%</TT
> is used, the word can be matched to any
     underscore-separated word within a label, regardless of position.
    </P
></LI
></UL
><P
>   Note: <TT
CLASS="TYPE"
>ltxtquery</TT
> allows whitespace between symbols, but
   <TT
CLASS="TYPE"
>ltree</TT
> and <TT
CLASS="TYPE"
>lquery</TT
> do not.
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN149503"
>F.21.2. Operators and Functions</A
></H2
><P
>   Type <TT
CLASS="TYPE"
>ltree</TT
> has the usual comparison operators
   <TT
CLASS="LITERAL"
>=</TT
>, <TT
CLASS="LITERAL"
>&lt;&gt;</TT
>,
   <TT
CLASS="LITERAL"
>&lt;</TT
>, <TT
CLASS="LITERAL"
>&gt;</TT
>, <TT
CLASS="LITERAL"
>&lt;=</TT
>, <TT
CLASS="LITERAL"
>&gt;=</TT
>.
   Comparison sorts in the order of a tree traversal, with the children
   of a node sorted by label text.  In addition, the specialized
   operators shown in <A
HREF="ltree.html#LTREE-OP-TABLE"
>Table F-14</A
> are available.
  </P
><DIV
CLASS="TABLE"
><A
NAME="LTREE-OP-TABLE"
></A
><P
><B
>Table F-14. <TT
CLASS="TYPE"
>ltree</TT
> Operators</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><THEAD
><TR
><TH
>Operator</TH
><TH
>Returns</TH
><TH
>Description</TH
></TR
></THEAD
><TBODY
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>@&gt;</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is left argument an ancestor of right (or equal)?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>&lt;@</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>is left argument a descendant of right (or equal)?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>~</TT
> <TT
CLASS="TYPE"
>lquery</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> match <TT
CLASS="TYPE"
>lquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>lquery</TT
> <TT
CLASS="LITERAL"
>~</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> match <TT
CLASS="TYPE"
>lquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>?</TT
> <TT
CLASS="TYPE"
>lquery[]</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> match any <TT
CLASS="TYPE"
>lquery</TT
> in array?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>lquery[]</TT
> <TT
CLASS="LITERAL"
>?</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> match any <TT
CLASS="TYPE"
>lquery</TT
> in array?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>@</TT
> <TT
CLASS="TYPE"
>ltxtquery</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> match <TT
CLASS="TYPE"
>ltxtquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltxtquery</TT
> <TT
CLASS="LITERAL"
>@</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> match <TT
CLASS="TYPE"
>ltxtquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>||</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>concatenate <TT
CLASS="TYPE"
>ltree</TT
> paths</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>||</TT
> <TT
CLASS="TYPE"
>text</TT
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>convert text to <TT
CLASS="TYPE"
>ltree</TT
> and concatenate</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>text</TT
> <TT
CLASS="LITERAL"
>||</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>convert text to <TT
CLASS="TYPE"
>ltree</TT
> and concatenate</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>@&gt;</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain an ancestor of <TT
CLASS="TYPE"
>ltree</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>&lt;@</TT
> <TT
CLASS="TYPE"
>ltree[]</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain an ancestor of <TT
CLASS="TYPE"
>ltree</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>&lt;@</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain a descendant of <TT
CLASS="TYPE"
>ltree</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree</TT
> <TT
CLASS="LITERAL"
>@&gt;</TT
> <TT
CLASS="TYPE"
>ltree[]</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain a descendant of <TT
CLASS="TYPE"
>ltree</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>~</TT
> <TT
CLASS="TYPE"
>lquery</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain any path matching <TT
CLASS="TYPE"
>lquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>lquery</TT
> <TT
CLASS="LITERAL"
>~</TT
> <TT
CLASS="TYPE"
>ltree[]</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain any path matching <TT
CLASS="TYPE"
>lquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>?</TT
> <TT
CLASS="TYPE"
>lquery[]</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> array contain any path matching any <TT
CLASS="TYPE"
>lquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>lquery[]</TT
> <TT
CLASS="LITERAL"
>?</TT
> <TT
CLASS="TYPE"
>ltree[]</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does <TT
CLASS="TYPE"
>ltree</TT
> array contain any path matching any <TT
CLASS="TYPE"
>lquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>@</TT
> <TT
CLASS="TYPE"
>ltxtquery</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain any path matching <TT
CLASS="TYPE"
>ltxtquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltxtquery</TT
> <TT
CLASS="LITERAL"
>@</TT
> <TT
CLASS="TYPE"
>ltree[]</TT
></TD
><TD
><TT
CLASS="TYPE"
>boolean</TT
></TD
><TD
>does array contain any path matching <TT
CLASS="TYPE"
>ltxtquery</TT
>?</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>?@&gt;</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>first array entry that is an ancestor of <TT
CLASS="TYPE"
>ltree</TT
>; NULL if none</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>?&lt;@</TT
> <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>first array entry that is a descendant of <TT
CLASS="TYPE"
>ltree</TT
>; NULL if none</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>?~</TT
> <TT
CLASS="TYPE"
>lquery</TT
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>first array entry that matches <TT
CLASS="TYPE"
>lquery</TT
>; NULL if none</TD
></TR
><TR
><TD
><TT
CLASS="TYPE"
>ltree[]</TT
> <TT
CLASS="LITERAL"
>?@</TT
> <TT
CLASS="TYPE"
>ltxtquery</TT
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>first array entry that matches <TT
CLASS="TYPE"
>ltxtquery</TT
>; NULL if none</TD
></TR
></TBODY
></TABLE
></DIV
><P
>   The operators <TT
CLASS="LITERAL"
>&lt;@</TT
>, <TT
CLASS="LITERAL"
>@&gt;</TT
>,
   <TT
CLASS="LITERAL"
>@</TT
> and <TT
CLASS="LITERAL"
>~</TT
> have analogues
   <TT
CLASS="LITERAL"
>^&lt;@</TT
>, <TT
CLASS="LITERAL"
>^@&gt;</TT
>, <TT
CLASS="LITERAL"
>^@</TT
>,
   <TT
CLASS="LITERAL"
>^~</TT
>, which are the same except they do not use
   indexes.  These are useful only for testing purposes.
  </P
><P
>   The available functions are shown in <A
HREF="ltree.html#LTREE-FUNC-TABLE"
>Table F-15</A
>.
  </P
><DIV
CLASS="TABLE"
><A
NAME="LTREE-FUNC-TABLE"
></A
><P
><B
>Table F-15. <TT
CLASS="TYPE"
>ltree</TT
> Functions</B
></P
><TABLE
BORDER="1"
CLASS="CALSTABLE"
><COL><COL><COL><COL><COL><THEAD
><TR
><TH
>Function</TH
><TH
>Return Type</TH
><TH
>Description</TH
><TH
>Example</TH
><TH
>Result</TH
></TR
></THEAD
><TBODY
><TR
><TD
><CODE
CLASS="FUNCTION"
>subltree(ltree, int start, int end)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>subpath of <TT
CLASS="TYPE"
>ltree</TT
> from position <TT
CLASS="PARAMETER"
>start</TT
> to
       position <TT
CLASS="PARAMETER"
>end</TT
>-1 (counting from 0)</TD
><TD
><TT
CLASS="LITERAL"
>subltree('Top.Child1.Child2',1,2)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>Child1</TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>subpath(ltree, int offset, int len)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>subpath of <TT
CLASS="TYPE"
>ltree</TT
> starting at position
       <TT
CLASS="PARAMETER"
>offset</TT
>, length <TT
CLASS="PARAMETER"
>len</TT
>.
       If <TT
CLASS="PARAMETER"
>offset</TT
> is negative, subpath starts that far from the
       end of the path.  If <TT
CLASS="PARAMETER"
>len</TT
> is negative, leaves that many
       labels off the end of the path.</TD
><TD
><TT
CLASS="LITERAL"
>subpath('Top.Child1.Child2',0,2)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>Top.Child1</TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>subpath(ltree, int offset)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>subpath of <TT
CLASS="TYPE"
>ltree</TT
> starting at position
       <TT
CLASS="PARAMETER"
>offset</TT
>, extending to end of path.
       If <TT
CLASS="PARAMETER"
>offset</TT
> is negative, subpath starts that far from the
       end of the path.</TD
><TD
><TT
CLASS="LITERAL"
>subpath('Top.Child1.Child2',1)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>Child1.Child2</TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>nlevel(ltree)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>number of labels in path</TD
><TD
><TT
CLASS="LITERAL"
>nlevel('Top.Child1.Child2')</TT
></TD
><TD
><TT
CLASS="LITERAL"
>3</TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>index(ltree a, ltree b)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>position of first occurrence of <TT
CLASS="PARAMETER"
>b</TT
> in
       <TT
CLASS="PARAMETER"
>a</TT
>; -1 if not found</TD
><TD
><TT
CLASS="LITERAL"
>index('0.1.2.3.5.4.5.6.8.5.6.8','5.6')</TT
></TD
><TD
><TT
CLASS="LITERAL"
>6</TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>index(ltree a, ltree b, int offset)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>integer</TT
></TD
><TD
>position of first occurrence of <TT
CLASS="PARAMETER"
>b</TT
> in
       <TT
CLASS="PARAMETER"
>a</TT
>, searching starting at <TT
CLASS="PARAMETER"
>offset</TT
>;
       negative <TT
CLASS="PARAMETER"
>offset</TT
> means start <TT
CLASS="PARAMETER"
>-offset</TT
>
       labels from the end of the path</TD
><TD
><TT
CLASS="LITERAL"
>index('0.1.2.3.5.4.5.6.8.5.6.8','5.6',-4)</TT
></TD
><TD
><TT
CLASS="LITERAL"
>9</TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>text2ltree(text)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>cast <TT
CLASS="TYPE"
>text</TT
> to <TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
><TT
CLASS="LITERAL"
></TT
></TD
><TD
><TT
CLASS="LITERAL"
></TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>ltree2text(ltree)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>text</TT
></TD
><TD
>cast <TT
CLASS="TYPE"
>ltree</TT
> to <TT
CLASS="TYPE"
>text</TT
></TD
><TD
><TT
CLASS="LITERAL"
></TT
></TD
><TD
><TT
CLASS="LITERAL"
></TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>lca(ltree, ltree, ...)</CODE
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>lowest common ancestor, i.e., longest common prefix of paths
       (up to 8 arguments supported)</TD
><TD
><TT
CLASS="LITERAL"
>lca('1.2.2.3','1.2.3.4.5.6')</TT
></TD
><TD
><TT
CLASS="LITERAL"
>1.2</TT
></TD
></TR
><TR
><TD
><CODE
CLASS="FUNCTION"
>lca(ltree[])</CODE
></TD
><TD
><TT
CLASS="TYPE"
>ltree</TT
></TD
><TD
>lowest common ancestor, i.e., longest common prefix of paths</TD
><TD
><TT
CLASS="LITERAL"
>lca(array['1.2.2.3'::ltree,'1.2.3'])</TT
></TD
><TD
><TT
CLASS="LITERAL"
>1.2</TT
></TD
></TR
></TBODY
></TABLE
></DIV
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN149900"
>F.21.3. Indexes</A
></H2
><P
>   <TT
CLASS="FILENAME"
>ltree</TT
> supports several types of indexes that can speed
   up the indicated operators:
  </P
><P
></P
><UL
><LI
><P
>     B-tree index over <TT
CLASS="TYPE"
>ltree</TT
>:
     <TT
CLASS="LITERAL"
>&lt;</TT
>, <TT
CLASS="LITERAL"
>&lt;=</TT
>, <TT
CLASS="LITERAL"
>=</TT
>,
     <TT
CLASS="LITERAL"
>&gt;=</TT
>, <TT
CLASS="LITERAL"
>&gt;</TT
>
    </P
></LI
><LI
><P
>     GiST index over <TT
CLASS="TYPE"
>ltree</TT
>:
     <TT
CLASS="LITERAL"
>&lt;</TT
>, <TT
CLASS="LITERAL"
>&lt;=</TT
>, <TT
CLASS="LITERAL"
>=</TT
>,
     <TT
CLASS="LITERAL"
>&gt;=</TT
>, <TT
CLASS="LITERAL"
>&gt;</TT
>,
     <TT
CLASS="LITERAL"
>@&gt;</TT
>, <TT
CLASS="LITERAL"
>&lt;@</TT
>,
     <TT
CLASS="LITERAL"
>@</TT
>, <TT
CLASS="LITERAL"
>~</TT
>, <TT
CLASS="LITERAL"
>?</TT
>
    </P
><P
>     Example of creating such an index:
    </P
><PRE
CLASS="PROGRAMLISTING"
>CREATE INDEX path_gist_idx ON test USING GIST (path);</PRE
></LI
><LI
><P
>     GiST index over <TT
CLASS="TYPE"
>ltree[]</TT
>:
     <TT
CLASS="LITERAL"
>ltree[] &lt;@ ltree</TT
>, <TT
CLASS="LITERAL"
>ltree @&gt; ltree[]</TT
>,
     <TT
CLASS="LITERAL"
>@</TT
>, <TT
CLASS="LITERAL"
>~</TT
>, <TT
CLASS="LITERAL"
>?</TT
>
    </P
><P
>     Example of creating such an index:
    </P
><PRE
CLASS="PROGRAMLISTING"
>CREATE INDEX path_gist_idx ON test USING GIST (array_path);</PRE
><P
>     Note: This index type is lossy.
    </P
></LI
></UL
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN149939"
>F.21.4. Example</A
></H2
><P
>   This example uses the following data (also available in file
   <TT
CLASS="FILENAME"
>contrib/ltree/ltreetest.sql</TT
> in the source distribution):
  </P
><PRE
CLASS="PROGRAMLISTING"
>CREATE TABLE test (path ltree);
INSERT INTO test VALUES ('Top');
INSERT INTO test VALUES ('Top.Science');
INSERT INTO test VALUES ('Top.Science.Astronomy');
INSERT INTO test VALUES ('Top.Science.Astronomy.Astrophysics');
INSERT INTO test VALUES ('Top.Science.Astronomy.Cosmology');
INSERT INTO test VALUES ('Top.Hobbies');
INSERT INTO test VALUES ('Top.Hobbies.Amateurs_Astronomy');
INSERT INTO test VALUES ('Top.Collections');
INSERT INTO test VALUES ('Top.Collections.Pictures');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Stars');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Galaxies');
INSERT INTO test VALUES ('Top.Collections.Pictures.Astronomy.Astronauts');
CREATE INDEX path_gist_idx ON test USING gist(path);
CREATE INDEX path_idx ON test USING btree(path);</PRE
><P
>   Now, we have a table <TT
CLASS="STRUCTNAME"
>test</TT
> populated with data describing
   the hierarchy shown below:
  </P
><PRE
CLASS="LITERALLAYOUT"
>                        Top
                     /   |  \
             Science Hobbies Collections
                 /       |              \
        Astronomy   Amateurs_Astronomy Pictures
           /  \                            |
Astrophysics  Cosmology                Astronomy
                                        /  |    \
                                 Galaxies Stars Astronauts</PRE
><P
>   We can do inheritance:
</P><PRE
CLASS="SCREEN"
>ltreetest=&gt; SELECT path FROM test WHERE path &lt;@ 'Top.Science';
                path
------------------------------------
 Top.Science
 Top.Science.Astronomy
 Top.Science.Astronomy.Astrophysics
 Top.Science.Astronomy.Cosmology
(4 rows)</PRE
><P>
  </P
><P
>   Here are some examples of path matching:
</P><PRE
CLASS="SCREEN"
>ltreetest=&gt; SELECT path FROM test WHERE path ~ '*.Astronomy.*';
                     path
-----------------------------------------------
 Top.Science.Astronomy
 Top.Science.Astronomy.Astrophysics
 Top.Science.Astronomy.Cosmology
 Top.Collections.Pictures.Astronomy
 Top.Collections.Pictures.Astronomy.Stars
 Top.Collections.Pictures.Astronomy.Galaxies
 Top.Collections.Pictures.Astronomy.Astronauts
(7 rows)

ltreetest=&gt; SELECT path FROM test WHERE path ~ '*.!pictures@.*.Astronomy.*';
                path
------------------------------------
 Top.Science.Astronomy
 Top.Science.Astronomy.Astrophysics
 Top.Science.Astronomy.Cosmology
(3 rows)</PRE
><P>
  </P
><P
>   Here are some examples of full text search:
</P><PRE
CLASS="SCREEN"
>ltreetest=&gt; SELECT path FROM test WHERE path @ 'Astro*% &amp; !pictures@';
                path
------------------------------------
 Top.Science.Astronomy
 Top.Science.Astronomy.Astrophysics
 Top.Science.Astronomy.Cosmology
 Top.Hobbies.Amateurs_Astronomy
(4 rows)

ltreetest=&gt; SELECT path FROM test WHERE path @ 'Astro* &amp; !pictures@';
                path
------------------------------------
 Top.Science.Astronomy
 Top.Science.Astronomy.Astrophysics
 Top.Science.Astronomy.Cosmology
(3 rows)</PRE
><P>
  </P
><P
>   Path construction using functions:
</P><PRE
CLASS="SCREEN"
>ltreetest=&gt; SELECT subpath(path,0,2)||'Space'||subpath(path,2) FROM test WHERE path &lt;@ 'Top.Science.Astronomy';
                 ?column?
------------------------------------------
 Top.Science.Space.Astronomy
 Top.Science.Space.Astronomy.Astrophysics
 Top.Science.Space.Astronomy.Cosmology
(3 rows)</PRE
><P>
  </P
><P
>   We could simplify this by creating a SQL function that inserts a label
   at a specified position in a path:
</P><PRE
CLASS="SCREEN"
>CREATE FUNCTION ins_label(ltree, int, text) RETURNS ltree
    AS 'select subpath($1,0,$2) || $3 || subpath($1,$2);'
    LANGUAGE SQL IMMUTABLE;

ltreetest=&gt; SELECT ins_label(path,2,'Space') FROM test WHERE path &lt;@ 'Top.Science.Astronomy';
                ins_label
------------------------------------------
 Top.Science.Space.Astronomy
 Top.Science.Space.Astronomy.Astrophysics
 Top.Science.Space.Astronomy.Cosmology
(3 rows)</PRE
><P>
  </P
></DIV
><DIV
CLASS="SECT2"
><H2
CLASS="SECT2"
><A
NAME="AEN149957"
>F.21.5. Authors</A
></H2
><P
>   All work was done by Teodor Sigaev (<CODE
CLASS="EMAIL"
>&#60;<A
HREF="mailto:teodor@stack.net"
>teodor@stack.net</A
>&#62;</CODE
>) and
   Oleg Bartunov (<CODE
CLASS="EMAIL"
>&#60;<A
HREF="mailto:oleg@sai.msu.su"
>oleg@sai.msu.su</A
>&#62;</CODE
>). See
   <A
HREF="http://www.sai.msu.su/~megera/postgres/gist/"
TARGET="_top"
>http://www.sai.msu.su/~megera/postgres/gist/</A
> for
   additional information. Authors would like to thank Eugeny Rodichev for
   helpful discussions. Comments and bug reports are welcome.
  </P
></DIV
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