summaryrefslogtreecommitdiffstats
path: root/doc/src/sgml/html/ltree.html
blob: a07bfc1f94055a7ec59a8ce3abec07bb41409474 (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>F.23. ltree</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="lo.html" title="F.22. lo" /><link rel="next" href="oldsnapshot.html" title="F.24. old_snapshot" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.23. ltree</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="lo.html" title="F.22. lo">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="oldsnapshot.html" title="F.24. old_snapshot">Next</a></td></tr></table><hr /></div><div class="sect1" id="LTREE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.23. ltree</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="ltree.html#id-1.11.7.32.5">F.23.1. Definitions</a></span></dt><dt><span class="sect2"><a href="ltree.html#id-1.11.7.32.6">F.23.2. Operators and Functions</a></span></dt><dt><span class="sect2"><a href="ltree.html#id-1.11.7.32.7">F.23.3. Indexes</a></span></dt><dt><span class="sect2"><a href="ltree.html#id-1.11.7.32.8">F.23.4. Example</a></span></dt><dt><span class="sect2"><a href="ltree.html#id-1.11.7.32.9">F.23.5. Transforms</a></span></dt><dt><span class="sect2"><a href="ltree.html#id-1.11.7.32.10">F.23.6. Authors</a></span></dt></dl></div><a id="id-1.11.7.32.2" class="indexterm"></a><p>
  This module implements a data type <code class="type">ltree</code> for representing
  labels of data stored in a hierarchical tree-like structure.
  Extensive facilities for searching through label trees are provided.
 </p><p>
  This module is considered <span class="quote"><span class="quote">trusted</span></span>, that is, it can be
  installed by non-superusers who have <code class="literal">CREATE</code> privilege
  on the current database.
 </p><div class="sect2" id="id-1.11.7.32.5"><div class="titlepage"><div><div><h3 class="title">F.23.1. Definitions</h3></div></div></div><p>
   A <em class="firstterm">label</em> is a sequence of alphanumeric characters
   and underscores (for example, in C locale the characters
   <code class="literal">A-Za-z0-9_</code> are allowed).
   Labels must be less than 256 characters long.
  </p><p>
   Examples: <code class="literal">42</code>, <code class="literal">Personal_Services</code>
  </p><p>
   A <em class="firstterm">label path</em> is a sequence of zero or more
   labels separated by dots, for example <code class="literal">L1.L2.L3</code>, representing
   a path from the root of a hierarchical tree to a particular node.  The
   length of a label path cannot exceed 65535 labels.
  </p><p>
   Example: <code class="literal">Top.Countries.Europe.Russia</code>
  </p><p>
   The <code class="filename">ltree</code> module provides several data types:
  </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
     <code class="type">ltree</code> stores a label path.
    </p></li><li class="listitem"><p>
     <code class="type">lquery</code> represents a regular-expression-like pattern
     for matching <code class="type">ltree</code> values.  A simple word matches that
     label within a path.  A star symbol (<code class="literal">*</code>) matches zero
     or more labels.  These can be joined with dots to form a pattern that
     must match the whole label path.  For example:
</p><pre class="synopsis">
foo         <em class="lineannotation"><span class="lineannotation">Match the exact label path <code class="literal">foo</code></span></em>
*.foo.*     <em class="lineannotation"><span class="lineannotation">Match any label path containing the label <code class="literal">foo</code></span></em>
*.foo       <em class="lineannotation"><span class="lineannotation">Match any label path whose last label is <code class="literal">foo</code></span></em>
</pre><p>
    </p><p>
     Both star symbols and simple words can be quantified to restrict how many
     labels they can match:
</p><pre class="synopsis">
*{<em class="replaceable"><code>n</code></em>}        <em class="lineannotation"><span class="lineannotation">Match exactly <em class="replaceable"><code>n</code></em> labels</span></em>
*{<em class="replaceable"><code>n</code></em>,}       <em class="lineannotation"><span class="lineannotation">Match at least <em class="replaceable"><code>n</code></em> labels</span></em>
*{<em class="replaceable"><code>n</code></em>,<em class="replaceable"><code>m</code></em>}      <em class="lineannotation"><span class="lineannotation">Match at least <em class="replaceable"><code>n</code></em> but not more than <em class="replaceable"><code>m</code></em> labels</span></em>
*{,<em class="replaceable"><code>m</code></em>}       <em class="lineannotation"><span class="lineannotation">Match at most <em class="replaceable"><code>m</code></em> labels — same as </span></em>*{0,<em class="replaceable"><code>m</code></em>}
foo{<em class="replaceable"><code>n</code></em>,<em class="replaceable"><code>m</code></em>}    <em class="lineannotation"><span class="lineannotation">Match at least <em class="replaceable"><code>n</code></em> but not more than <em class="replaceable"><code>m</code></em> occurrences of <code class="literal">foo</code></span></em>
foo{,}      <em class="lineannotation"><span class="lineannotation">Match any number of occurrences of <code class="literal">foo</code>, including zero</span></em>
</pre><p>
     In the absence of any explicit quantifier, the default for a star symbol
     is to match any number of labels (that is, <code class="literal">{,}</code>) while
     the default for a non-star item is to match exactly once (that
     is, <code class="literal">{1}</code>).
    </p><p>
     There are several modifiers that can be put at the end of a non-star
     <code class="type">lquery</code> item to make it match more than just the exact match:
</p><pre class="synopsis">
@           <em class="lineannotation"><span class="lineannotation">Match case-insensitively, for example <code class="literal">a@</code> matches <code class="literal">A</code></span></em>
*           <em class="lineannotation"><span class="lineannotation">Match any label with this prefix, for example <code class="literal">foo*</code> matches <code class="literal">foobar</code></span></em>
%           <em class="lineannotation"><span class="lineannotation">Match initial underscore-separated words</span></em>
</pre><p>
     The behavior of <code class="literal">%</code> is a bit complicated.  It tries to match
     words rather than the entire label.  For example
     <code class="literal">foo_bar%</code> matches <code class="literal">foo_bar_baz</code> but not
     <code class="literal">foo_barbaz</code>.  If combined with <code class="literal">*</code>, prefix
     matching applies to each word separately, for example
     <code class="literal">foo_bar%*</code> matches <code class="literal">foo1_bar2_baz</code> but
     not <code class="literal">foo1_br2_baz</code>.
    </p><p>
     Also, you can write several possibly-modified non-star items separated with
     <code class="literal">|</code> (OR) to match any of those items, and you can put
     <code class="literal">!</code> (NOT) at the start of a non-star group to match any
     label that doesn't match any of the alternatives.  A quantifier, if any,
     goes at the end of the group; it means some number of matches for the
     group as a whole (that is, some number of labels matching or not matching
     any of the alternatives).
    </p><p>
     Here's an annotated example of <code class="type">lquery</code>:
</p><pre class="programlisting">
Top.*{0,2}.sport*@.!football|tennis{1,}.Russ*|Spain
a.  b.     c.      d.                   e.
</pre><p>
     This query will match any label path that:
    </p><div class="orderedlist"><ol class="orderedlist" type="a"><li class="listitem"><p>
       begins with the label <code class="literal">Top</code>
      </p></li><li class="listitem"><p>
       and next has zero to two labels before
      </p></li><li class="listitem"><p>
       a label beginning with the case-insensitive prefix <code class="literal">sport</code>
      </p></li><li class="listitem"><p>
       then has one or more labels, none of which
       match <code class="literal">football</code> nor <code class="literal">tennis</code>
      </p></li><li class="listitem"><p>
       and then ends with a label beginning with <code class="literal">Russ</code> or
       exactly matching <code class="literal">Spain</code>.
      </p></li></ol></div></li><li class="listitem"><p><code class="type">ltxtquery</code> represents a full-text-search-like
    pattern for matching <code class="type">ltree</code> values.  An
    <code class="type">ltxtquery</code> value contains words, possibly with the
    modifiers <code class="literal">@</code>, <code class="literal">*</code>, <code class="literal">%</code> at the end;
    the modifiers have the same meanings as in <code class="type">lquery</code>.
    Words can be combined with <code class="literal">&amp;</code> (AND),
    <code class="literal">|</code> (OR), <code class="literal">!</code> (NOT), and parentheses.
    The key difference from
    <code class="type">lquery</code> is that <code class="type">ltxtquery</code> matches words without
    regard to their position in the label path.
    </p><p>
     Here's an example <code class="type">ltxtquery</code>:
</p><pre class="programlisting">
Europe &amp; Russia*@ &amp; !Transportation
</pre><p>
     This will match paths that contain the label <code class="literal">Europe</code> and
     any label beginning with <code class="literal">Russia</code> (case-insensitive),
     but not paths containing the label <code class="literal">Transportation</code>.
     The location of these words within the path is not important.
     Also, when <code class="literal">%</code> is used, the word can be matched to any
     underscore-separated word within a label, regardless of position.
    </p></li></ul></div><p>
   Note: <code class="type">ltxtquery</code> allows whitespace between symbols, but
   <code class="type">ltree</code> and <code class="type">lquery</code> do not.
  </p></div><div class="sect2" id="id-1.11.7.32.6"><div class="titlepage"><div><div><h3 class="title">F.23.2. Operators and Functions</h3></div></div></div><p>
   Type <code class="type">ltree</code> has the usual comparison operators
   <code class="literal">=</code>, <code class="literal">&lt;&gt;</code>,
   <code class="literal">&lt;</code>, <code class="literal">&gt;</code>, <code class="literal">&lt;=</code>, <code class="literal">&gt;=</code>.
   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 class="xref" href="ltree.html#LTREE-OP-TABLE" title="Table F.13. ltree Operators">Table F.13</a> are available.
  </p><div class="table" id="LTREE-OP-TABLE"><p class="title"><strong>Table F.13. <code class="type">ltree</code> Operators</strong></p><div class="table-contents"><table class="table" summary="ltree Operators" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
        Operator
       </p>
       <p>
        Description
       </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree</code> <code class="literal">@&gt;</code> <code class="type">ltree</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Is left argument an ancestor of right (or equal)?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree</code> <code class="literal">&lt;@</code> <code class="type">ltree</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Is left argument a descendant of right (or equal)?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree</code> <code class="literal">~</code> <code class="type">lquery</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">lquery</code> <code class="literal">~</code> <code class="type">ltree</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does <code class="type">ltree</code> match <code class="type">lquery</code>?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree</code> <code class="literal">?</code> <code class="type">lquery[]</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">lquery[]</code> <code class="literal">?</code> <code class="type">ltree</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does <code class="type">ltree</code> match any <code class="type">lquery</code> in array?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree</code> <code class="literal">@</code> <code class="type">ltxtquery</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">ltxtquery</code> <code class="literal">@</code> <code class="type">ltree</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does <code class="type">ltree</code> match <code class="type">ltxtquery</code>?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree</code> <code class="literal">||</code> <code class="type">ltree</code><code class="returnvalue">ltree</code>
       </p>
       <p>
        Concatenates <code class="type">ltree</code> paths.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree</code> <code class="literal">||</code> <code class="type">text</code><code class="returnvalue">ltree</code>
       </p>
       <p class="func_signature">
        <code class="type">text</code> <code class="literal">||</code> <code class="type">ltree</code><code class="returnvalue">ltree</code>
       </p>
       <p>
        Converts text to <code class="type">ltree</code> and concatenates.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">@&gt;</code> <code class="type">ltree</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">ltree</code> <code class="literal">&lt;@</code> <code class="type">ltree[]</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does array contain an ancestor of <code class="type">ltree</code>?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">&lt;@</code> <code class="type">ltree</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">ltree</code> <code class="literal">@&gt;</code> <code class="type">ltree[]</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does array contain a descendant of <code class="type">ltree</code>?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">~</code> <code class="type">lquery</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">lquery</code> <code class="literal">~</code> <code class="type">ltree[]</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does array contain any path matching <code class="type">lquery</code>?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">?</code> <code class="type">lquery[]</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">lquery[]</code> <code class="literal">?</code> <code class="type">ltree[]</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does <code class="type">ltree</code> array contain any path matching
        any <code class="type">lquery</code>?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">@</code> <code class="type">ltxtquery</code><code class="returnvalue">boolean</code>
       </p>
       <p class="func_signature">
        <code class="type">ltxtquery</code> <code class="literal">@</code> <code class="type">ltree[]</code><code class="returnvalue">boolean</code>
       </p>
       <p>
        Does array contain any path matching <code class="type">ltxtquery</code>?
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">?@&gt;</code> <code class="type">ltree</code><code class="returnvalue">ltree</code>
       </p>
       <p>
        Returns first array entry that is an ancestor of <code class="type">ltree</code>,
        or <code class="literal">NULL</code> if none.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">?&lt;@</code> <code class="type">ltree</code><code class="returnvalue">ltree</code>
       </p>
       <p>
        Returns first array entry that is a descendant of <code class="type">ltree</code>,
        or <code class="literal">NULL</code> if none.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">?~</code> <code class="type">lquery</code><code class="returnvalue">ltree</code>
       </p>
       <p>
        Returns first array entry that matches <code class="type">lquery</code>,
        or <code class="literal">NULL</code> if none.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="type">ltree[]</code> <code class="literal">?@</code> <code class="type">ltxtquery</code><code class="returnvalue">ltree</code>
       </p>
       <p>
        Returns first array entry that matches <code class="type">ltxtquery</code>,
        or <code class="literal">NULL</code> if none.
       </p></td></tr></tbody></table></div></div><br class="table-break" /><p>
   The operators <code class="literal">&lt;@</code>, <code class="literal">@&gt;</code>,
   <code class="literal">@</code> and <code class="literal">~</code> have analogues
   <code class="literal">^&lt;@</code>, <code class="literal">^@&gt;</code>, <code class="literal">^@</code>,
   <code class="literal">^~</code>, 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 class="xref" href="ltree.html#LTREE-FUNC-TABLE" title="Table F.14. ltree Functions">Table F.14</a>.
  </p><div class="table" id="LTREE-FUNC-TABLE"><p class="title"><strong>Table F.14. <code class="type">ltree</code> Functions</strong></p><div class="table-contents"><table class="table" summary="ltree Functions" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
        Function
       </p>
       <p>
        Description
       </p>
       <p>
        Example(s)
       </p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.11.7.32.6.6.2.2.1.1.1.1" class="indexterm"></a>
        <code class="function">subltree</code> ( <code class="type">ltree</code>, <em class="parameter"><code>start</code></em> <code class="type">integer</code>, <em class="parameter"><code>end</code></em> <code class="type">integer</code> )
        → <code class="returnvalue">ltree</code>
       </p>
       <p>
        Returns subpath of <code class="type">ltree</code> from
        position <em class="parameter"><code>start</code></em> to
        position <em class="parameter"><code>end</code></em>-1 (counting from 0).
       </p>
       <p>
        <code class="literal">subltree('Top.Child1.Child2', 1, 2)</code><code class="returnvalue">Child1</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.11.7.32.6.6.2.2.2.1.1.1" class="indexterm"></a>
        <code class="function">subpath</code> ( <code class="type">ltree</code>, <em class="parameter"><code>offset</code></em> <code class="type">integer</code>, <em class="parameter"><code>len</code></em> <code class="type">integer</code> )
        → <code class="returnvalue">ltree</code>
       </p>
       <p>
        Returns subpath of <code class="type">ltree</code> starting at
        position <em class="parameter"><code>offset</code></em>, with
        length <em class="parameter"><code>len</code></em>.  If <em class="parameter"><code>offset</code></em>
        is negative, subpath starts that far from the end of the path.
        If <em class="parameter"><code>len</code></em> is negative, leaves that many labels off
        the end of the path.
       </p>
       <p>
        <code class="literal">subpath('Top.Child1.Child2', 0, 2)</code><code class="returnvalue">Top.Child1</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="function">subpath</code> ( <code class="type">ltree</code>, <em class="parameter"><code>offset</code></em> <code class="type">integer</code> )
        → <code class="returnvalue">ltree</code>
       </p>
       <p>
        Returns subpath of <code class="type">ltree</code> starting at
        position <em class="parameter"><code>offset</code></em>, extending to end of path.
        If <em class="parameter"><code>offset</code></em> is negative, subpath starts that far
        from the end of the path.
       </p>
       <p>
        <code class="literal">subpath('Top.Child1.Child2', 1)</code><code class="returnvalue">Child1.Child2</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.11.7.32.6.6.2.2.4.1.1.1" class="indexterm"></a>
        <code class="function">nlevel</code> ( <code class="type">ltree</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns number of labels in path.
       </p>
       <p>
        <code class="literal">nlevel('Top.Child1.Child2')</code><code class="returnvalue">3</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.11.7.32.6.6.2.2.5.1.1.1" class="indexterm"></a>
        <code class="function">index</code> ( <em class="parameter"><code>a</code></em> <code class="type">ltree</code>, <em class="parameter"><code>b</code></em> <code class="type">ltree</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns position of first occurrence of <em class="parameter"><code>b</code></em> in
        <em class="parameter"><code>a</code></em>, or -1 if not found.
       </p>
       <p>
        <code class="literal">index('0.1.2.3.5.4.5.6.8.5.6.8', '5.6')</code><code class="returnvalue">6</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="function">index</code> ( <em class="parameter"><code>a</code></em> <code class="type">ltree</code>,  <em class="parameter"><code>b</code></em> <code class="type">ltree</code>, <em class="parameter"><code>offset</code></em> <code class="type">integer</code> )
        → <code class="returnvalue">integer</code>
       </p>
       <p>
        Returns position of first occurrence of <em class="parameter"><code>b</code></em>
        in <em class="parameter"><code>a</code></em>, or -1 if not found.  The search starts at
        position <em class="parameter"><code>offset</code></em>;
        negative <em class="parameter"><code>offset</code></em> means
        start <em class="parameter"><code>-offset</code></em> labels from the end of the path.
       </p>
       <p>
        <code class="literal">index('0.1.2.3.5.4.5.6.8.5.6.8', '5.6', -4)</code><code class="returnvalue">9</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.11.7.32.6.6.2.2.7.1.1.1" class="indexterm"></a>
        <code class="function">text2ltree</code> ( <code class="type">text</code> )
        → <code class="returnvalue">ltree</code>
       </p>
       <p>
        Casts <code class="type">text</code> to <code class="type">ltree</code>.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.11.7.32.6.6.2.2.8.1.1.1" class="indexterm"></a>
        <code class="function">ltree2text</code> ( <code class="type">ltree</code> )
        → <code class="returnvalue">text</code>
       </p>
       <p>
        Casts <code class="type">ltree</code> to <code class="type">text</code>.
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <a id="id-1.11.7.32.6.6.2.2.9.1.1.1" class="indexterm"></a>
        <code class="function">lca</code> ( <code class="type">ltree</code> [<span class="optional">, <code class="type">ltree</code> [<span class="optional">, ... </span>]</span>] )
        → <code class="returnvalue">ltree</code>
       </p>
       <p>
        Computes longest common ancestor of paths
        (up to 8 arguments are supported).
       </p>
       <p>
        <code class="literal">lca('1.2.3', '1.2.3.4.5.6')</code><code class="returnvalue">1.2</code>
       </p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
        <code class="function">lca</code> ( <code class="type">ltree[]</code> )
        → <code class="returnvalue">ltree</code>
       </p>
       <p>
        Computes longest common ancestor of paths in array.
       </p>
       <p>
        <code class="literal">lca(array['1.2.3'::ltree,'1.2.3.4'])</code><code class="returnvalue">1.2</code>
       </p></td></tr></tbody></table></div></div><br class="table-break" /></div><div class="sect2" id="id-1.11.7.32.7"><div class="titlepage"><div><div><h3 class="title">F.23.3. Indexes</h3></div></div></div><p>
   <code class="filename">ltree</code> supports several types of indexes that can speed
   up the indicated operators:
  </p><div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; "><li class="listitem"><p>
     B-tree index over <code class="type">ltree</code>:
     <code class="literal">&lt;</code>, <code class="literal">&lt;=</code>, <code class="literal">=</code>,
     <code class="literal">&gt;=</code>, <code class="literal">&gt;</code>
    </p></li><li class="listitem"><p>
     GiST index over <code class="type">ltree</code> (<code class="literal">gist_ltree_ops</code>
     opclass):
     <code class="literal">&lt;</code>, <code class="literal">&lt;=</code>, <code class="literal">=</code>,
     <code class="literal">&gt;=</code>, <code class="literal">&gt;</code>,
     <code class="literal">@&gt;</code>, <code class="literal">&lt;@</code>,
     <code class="literal">@</code>, <code class="literal">~</code>, <code class="literal">?</code>
    </p><p>
     <code class="literal">gist_ltree_ops</code> GiST opclass approximates a set of
     path labels as a bitmap signature.  Its optional integer parameter
     <code class="literal">siglen</code> determines the
     signature length in bytes.  The default signature length is 8 bytes.
     The length must be a positive multiple of <code class="type">int</code> alignment
     (4 bytes on most machines)) up to 2024.  Longer
     signatures lead to a more precise search (scanning a smaller fraction of the index and
     fewer heap pages), at the cost of a larger index.
    </p><p>
     Example of creating such an index with the default signature length of 8 bytes:
    </p><pre class="programlisting">
CREATE INDEX path_gist_idx ON test USING GIST (path);
</pre><p>
     Example of creating such an index with a signature length of 100 bytes:
    </p><pre class="programlisting">
CREATE INDEX path_gist_idx ON test USING GIST (path gist_ltree_ops(siglen=100));
</pre></li><li class="listitem"><p>
     GiST index over <code class="type">ltree[]</code> (<code class="literal">gist__ltree_ops</code>
     opclass):
     <code class="literal">ltree[] &lt;@ ltree</code>, <code class="literal">ltree @&gt; ltree[]</code>,
     <code class="literal">@</code>, <code class="literal">~</code>, <code class="literal">?</code>
    </p><p>
     <code class="literal">gist__ltree_ops</code> GiST opclass works similarly to
     <code class="literal">gist_ltree_ops</code> and also takes signature length as
     a parameter.  The default value of <code class="literal">siglen</code> in
      <code class="literal">gist__ltree_ops</code> is 28 bytes.
    </p><p>
     Example of creating such an index with the default signature length of 28 bytes:
    </p><pre class="programlisting">
CREATE INDEX path_gist_idx ON test USING GIST (array_path);
</pre><p>
     Example of creating such an index with a signature length of 100 bytes:
    </p><pre class="programlisting">
CREATE INDEX path_gist_idx ON test USING GIST (array_path gist__ltree_ops(siglen=100));
</pre><p>
     Note: This index type is lossy.
    </p></li></ul></div></div><div class="sect2" id="id-1.11.7.32.8"><div class="titlepage"><div><div><h3 class="title">F.23.4. Example</h3></div></div></div><p>
   This example uses the following data (also available in file
   <code class="filename">contrib/ltree/ltreetest.sql</code> 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 <code class="structname">test</code> 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 an 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" id="id-1.11.7.32.9"><div class="titlepage"><div><div><h3 class="title">F.23.5. Transforms</h3></div></div></div><p>
   The <code class="literal">ltree_plpython3u</code> extension implements transforms for
   the <code class="type">ltree</code> type for PL/Python. If installed and specified when
   creating a function, <code class="type">ltree</code> values are mapped to Python lists.
   (The reverse is currently not supported, however.)
  </p><div class="caution"><h3 class="title">Caution</h3><p>
    It is strongly recommended that the transform extension be installed in
    the same schema as <code class="filename">ltree</code>.  Otherwise there are
    installation-time security hazards if a transform extension's schema
    contains objects defined by a hostile user.
   </p></div></div><div class="sect2" id="id-1.11.7.32.10"><div class="titlepage"><div><div><h3 class="title">F.23.6. Authors</h3></div></div></div><p>
   All work was done by Teodor Sigaev (<code class="email">&lt;<a class="email" href="mailto:teodor@stack.net">teodor@stack.net</a>&gt;</code>) and
   Oleg Bartunov (<code class="email">&lt;<a class="email" href="mailto:oleg@sai.msu.su">oleg@sai.msu.su</a>&gt;</code>). See
   <a class="ulink" 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></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="lo.html" title="F.22. lo">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="oldsnapshot.html" title="F.24. old_snapshot">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.22. lo </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.7 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.24. old_snapshot</td></tr></table></div></body></html>