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
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
|
<?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.18. hstore — hstore key/value datatype</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="fuzzystrmatch.html" title="F.17. fuzzystrmatch — determine string similarities and distance" /><link rel="next" href="intagg.html" title="F.19. intagg — integer aggregator and enumerator" /></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.18. hstore — hstore key/value datatype</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="fuzzystrmatch.html" title="F.17. fuzzystrmatch — determine string similarities and distance">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules and Extensions">Up</a></td><th width="60%" align="center">Appendix F. Additional Supplied Modules and Extensions</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="intagg.html" title="F.19. intagg — integer aggregator and enumerator">Next</a></td></tr></table><hr /></div><div class="sect1" id="HSTORE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.18. hstore — hstore key/value datatype <a href="#HSTORE" class="id_link">#</a></h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="hstore.html#HSTORE-EXTERNAL-REP">F.18.1. <code class="type">hstore</code> External Representation</a></span></dt><dt><span class="sect2"><a href="hstore.html#HSTORE-OPS-FUNCS">F.18.2. <code class="type">hstore</code> Operators and Functions</a></span></dt><dt><span class="sect2"><a href="hstore.html#HSTORE-INDEXES">F.18.3. Indexes</a></span></dt><dt><span class="sect2"><a href="hstore.html#HSTORE-EXAMPLES">F.18.4. Examples</a></span></dt><dt><span class="sect2"><a href="hstore.html#HSTORE-STATISTICS">F.18.5. Statistics</a></span></dt><dt><span class="sect2"><a href="hstore.html#HSTORE-COMPATIBILITY">F.18.6. Compatibility</a></span></dt><dt><span class="sect2"><a href="hstore.html#HSTORE-TRANSFORMS">F.18.7. Transforms</a></span></dt><dt><span class="sect2"><a href="hstore.html#HSTORE-AUTHORS">F.18.8. Authors</a></span></dt></dl></div><a id="id-1.11.7.28.2" class="indexterm"></a><p>
This module implements the <code class="type">hstore</code> data type for storing sets of
key/value pairs within a single <span class="productname">PostgreSQL</span> value.
This can be useful in various scenarios, such as rows with many attributes
that are rarely examined, or semi-structured data. Keys and values are
simply text strings.
</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="HSTORE-EXTERNAL-REP"><div class="titlepage"><div><div><h3 class="title">F.18.1. <code class="type">hstore</code> External Representation <a href="#HSTORE-EXTERNAL-REP" class="id_link">#</a></h3></div></div></div><p>
The text representation of an <code class="type">hstore</code>, used for input and output,
includes zero or more <em class="replaceable"><code>key</code></em> <code class="literal">=></code>
<em class="replaceable"><code>value</code></em> pairs separated by commas. Some examples:
</p><pre class="synopsis">
k => v
foo => bar, baz => whatever
"1-a" => "anything at all"
</pre><p>
The order of the pairs is not significant (and may not be reproduced on
output). Whitespace between pairs or around the <code class="literal">=></code> sign is
ignored. Double-quote keys and values that include whitespace, commas,
<code class="literal">=</code>s or <code class="literal">></code>s. To include a double quote or a
backslash in a key or value, escape it with a backslash.
</p><p>
Each key in an <code class="type">hstore</code> is unique. If you declare an <code class="type">hstore</code>
with duplicate keys, only one will be stored in the <code class="type">hstore</code> and
there is no guarantee as to which will be kept:
</p><pre class="programlisting">
SELECT 'a=>1,a=>2'::hstore;
hstore
----------
"a"=>"1"
</pre><p>
</p><p>
A value (but not a key) can be an SQL <code class="literal">NULL</code>. For example:
</p><pre class="programlisting">
key => NULL
</pre><p>
The <code class="literal">NULL</code> keyword is case-insensitive. Double-quote the
<code class="literal">NULL</code> to treat it as the ordinary string <span class="quote">“<span class="quote">NULL</span>”</span>.
</p><div class="note"><h3 class="title">Note</h3><p>
Keep in mind that the <code class="type">hstore</code> text format, when used for input,
applies <span class="emphasis"><em>before</em></span> any required quoting or escaping. If you are
passing an <code class="type">hstore</code> literal via a parameter, then no additional
processing is needed. But if you're passing it as a quoted literal
constant, then any single-quote characters and (depending on the setting of
the <code class="varname">standard_conforming_strings</code> configuration parameter)
backslash characters need to be escaped correctly. See
<a class="xref" href="sql-syntax-lexical.html#SQL-SYNTAX-STRINGS" title="4.1.2.1. String Constants">Section 4.1.2.1</a> for more on the handling of string
constants.
</p></div><p>
On output, double quotes always surround keys and values, even when it's
not strictly necessary.
</p></div><div class="sect2" id="HSTORE-OPS-FUNCS"><div class="titlepage"><div><div><h3 class="title">F.18.2. <code class="type">hstore</code> Operators and Functions <a href="#HSTORE-OPS-FUNCS" class="id_link">#</a></h3></div></div></div><p>
The operators provided by the <code class="literal">hstore</code> module are
shown in <a class="xref" href="hstore.html#HSTORE-OP-TABLE" title="Table F.7. hstore Operators">Table F.7</a>, the functions
in <a class="xref" href="hstore.html#HSTORE-FUNC-TABLE" title="Table F.8. hstore Functions">Table F.8</a>.
</p><div class="table" id="HSTORE-OP-TABLE"><p class="title"><strong>Table F.7. <code class="type">hstore</code> Operators</strong></p><div class="table-contents"><table class="table" summary="hstore Operators" border="1"><colgroup><col /></colgroup><thead><tr><th class="func_table_entry"><p class="func_signature">
Operator
</p>
<p>
Description
</p>
<p>
Example(s)
</p></th></tr></thead><tbody><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">-></code> <code class="type">text</code>
→ <code class="returnvalue">text</code>
</p>
<p>
Returns value associated with given key, or <code class="literal">NULL</code> if
not present.
</p>
<p>
<code class="literal">'a=>x, b=>y'::hstore -> 'a'</code>
→ <code class="returnvalue">x</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">-></code> <code class="type">text[]</code>
→ <code class="returnvalue">text[]</code>
</p>
<p>
Returns values associated with given keys, or <code class="literal">NULL</code>
if not present.
</p>
<p>
<code class="literal">'a=>x, b=>y, c=>z'::hstore -> ARRAY['c','a']</code>
→ <code class="returnvalue">{"z","x"}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">||</code> <code class="type">hstore</code>
→ <code class="returnvalue">hstore</code>
</p>
<p>
Concatenates two <code class="type">hstore</code>s.
</p>
<p>
<code class="literal">'a=>b, c=>d'::hstore || 'c=>x, d=>q'::hstore</code>
→ <code class="returnvalue">"a"=>"b", "c"=>"x", "d"=>"q"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">?</code> <code class="type">text</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Does <code class="type">hstore</code> contain key?
</p>
<p>
<code class="literal">'a=>1'::hstore ? 'a'</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">?&</code> <code class="type">text[]</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Does <code class="type">hstore</code> contain all the specified keys?
</p>
<p>
<code class="literal">'a=>1,b=>2'::hstore ?& ARRAY['a','b']</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">?|</code> <code class="type">text[]</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Does <code class="type">hstore</code> contain any of the specified keys?
</p>
<p>
<code class="literal">'a=>1,b=>2'::hstore ?| ARRAY['b','c']</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">@></code> <code class="type">hstore</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Does left operand contain right?
</p>
<p>
<code class="literal">'a=>b, b=>1, c=>NULL'::hstore @> 'b=>1'</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal"><@</code> <code class="type">hstore</code>
→ <code class="returnvalue">boolean</code>
</p>
<p>
Is left operand contained in right?
</p>
<p>
<code class="literal">'a=>c'::hstore <@ 'a=>b, b=>1, c=>NULL'</code>
→ <code class="returnvalue">f</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">-</code> <code class="type">text</code>
→ <code class="returnvalue">hstore</code>
</p>
<p>
Deletes key from left operand.
</p>
<p>
<code class="literal">'a=>1, b=>2, c=>3'::hstore - 'b'::text</code>
→ <code class="returnvalue">"a"=>"1", "c"=>"3"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">-</code> <code class="type">text[]</code>
→ <code class="returnvalue">hstore</code>
</p>
<p>
Deletes keys from left operand.
</p>
<p>
<code class="literal">'a=>1, b=>2, c=>3'::hstore - ARRAY['a','b']</code>
→ <code class="returnvalue">"c"=>"3"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">hstore</code> <code class="literal">-</code> <code class="type">hstore</code>
→ <code class="returnvalue">hstore</code>
</p>
<p>
Deletes pairs from left operand that match pairs in the right operand.
</p>
<p>
<code class="literal">'a=>1, b=>2, c=>3'::hstore - 'a=>4, b=>2'::hstore</code>
→ <code class="returnvalue">"a"=>"1", "c"=>"3"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="type">anyelement</code> <code class="literal">#=</code> <code class="type">hstore</code>
→ <code class="returnvalue">anyelement</code>
</p>
<p>
Replaces fields in the left operand (which must be a composite type)
with matching values from <code class="type">hstore</code>.
</p>
<p>
<code class="literal">ROW(1,3) #= 'f1=>11'::hstore</code>
→ <code class="returnvalue">(11,3)</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="literal">%%</code> <code class="type">hstore</code>
→ <code class="returnvalue">text[]</code>
</p>
<p>
Converts <code class="type">hstore</code> to an array of alternating keys and
values.
</p>
<p>
<code class="literal">%% 'a=>foo, b=>bar'::hstore</code>
→ <code class="returnvalue">{a,foo,b,bar}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="literal">%#</code> <code class="type">hstore</code>
→ <code class="returnvalue">text[]</code>
</p>
<p>
Converts <code class="type">hstore</code> to a two-dimensional key/value array.
</p>
<p>
<code class="literal">%# 'a=>foo, b=>bar'::hstore</code>
→ <code class="returnvalue">{{a,foo},{b,bar}}</code>
</p></td></tr></tbody></table></div></div><br class="table-break" /><div class="table" id="HSTORE-FUNC-TABLE"><p class="title"><strong>Table F.8. <code class="type">hstore</code> Functions</strong></p><div class="table-contents"><table class="table" summary="hstore 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-1.11.7.28.6.4.2.2.1.1.1.1" class="indexterm"></a>
<code class="function">hstore</code> ( <code class="type">record</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Constructs an <code class="type">hstore</code> from a record or row.
</p>
<p>
<code class="literal">hstore(ROW(1,2))</code>
→ <code class="returnvalue">"f1"=>"1", "f2"=>"2"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">hstore</code> ( <code class="type">text[]</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Constructs an <code class="type">hstore</code> from an array, which may be either
a key/value array, or a two-dimensional array.
</p>
<p>
<code class="literal">hstore(ARRAY['a','1','b','2'])</code>
→ <code class="returnvalue">"a"=>"1", "b"=>"2"</code>
</p>
<p>
<code class="literal">hstore(ARRAY[['c','3'],['d','4']])</code>
→ <code class="returnvalue">"c"=>"3", "d"=>"4"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">hstore</code> ( <code class="type">text[]</code>, <code class="type">text[]</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Constructs an <code class="type">hstore</code> from separate key and value arrays.
</p>
<p>
<code class="literal">hstore(ARRAY['a','b'], ARRAY['1','2'])</code>
→ <code class="returnvalue">"a"=>"1", "b"=>"2"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">hstore</code> ( <code class="type">text</code>, <code class="type">text</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Makes a single-item <code class="type">hstore</code>.
</p>
<p>
<code class="literal">hstore('a', 'b')</code>
→ <code class="returnvalue">"a"=>"b"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.5.1.1.1" class="indexterm"></a>
<code class="function">akeys</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">text[]</code>
</p>
<p>
Extracts an <code class="type">hstore</code>'s keys as an array.
</p>
<p>
<code class="literal">akeys('a=>1,b=>2')</code>
→ <code class="returnvalue">{a,b}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.6.1.1.1" class="indexterm"></a>
<code class="function">skeys</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">setof text</code>
</p>
<p>
Extracts an <code class="type">hstore</code>'s keys as a set.
</p>
<p>
<code class="literal">skeys('a=>1,b=>2')</code>
→ <code class="returnvalue"></code>
</p><pre class="programlisting">
a
b
</pre><p>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.7.1.1.1" class="indexterm"></a>
<code class="function">avals</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">text[]</code>
</p>
<p>
Extracts an <code class="type">hstore</code>'s values as an array.
</p>
<p>
<code class="literal">avals('a=>1,b=>2')</code>
→ <code class="returnvalue">{1,2}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.8.1.1.1" class="indexterm"></a>
<code class="function">svals</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">setof text</code>
</p>
<p>
Extracts an <code class="type">hstore</code>'s values as a set.
</p>
<p>
<code class="literal">svals('a=>1,b=>2')</code>
→ <code class="returnvalue"></code>
</p><pre class="programlisting">
1
2
</pre><p>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.9.1.1.1" class="indexterm"></a>
<code class="function">hstore_to_array</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">text[]</code>
</p>
<p>
Extracts an <code class="type">hstore</code>'s keys and values as an array of
alternating keys and values.
</p>
<p>
<code class="literal">hstore_to_array('a=>1,b=>2')</code>
→ <code class="returnvalue">{a,1,b,2}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.10.1.1.1" class="indexterm"></a>
<code class="function">hstore_to_matrix</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">text[]</code>
</p>
<p>
Extracts an <code class="type">hstore</code>'s keys and values as a two-dimensional
array.
</p>
<p>
<code class="literal">hstore_to_matrix('a=>1,b=>2')</code>
→ <code class="returnvalue">{{a,1},{b,2}}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.11.1.1.1" class="indexterm"></a>
<code class="function">hstore_to_json</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">json</code>
</p>
<p>
Converts an <code class="type">hstore</code> to a <code class="type">json</code> value,
converting all non-null values to JSON strings.
</p>
<p>
This function is used implicitly when an <code class="type">hstore</code> value is
cast to <code class="type">json</code>.
</p>
<p>
<code class="literal">hstore_to_json('"a key"=>1, b=>t, c=>null, d=>12345, e=>012345, f=>1.234, g=>2.345e+4')</code>
→ <code class="returnvalue">{"a key": "1", "b": "t", "c": null, "d": "12345", "e": "012345", "f": "1.234", "g": "2.345e+4"}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.12.1.1.1" class="indexterm"></a>
<code class="function">hstore_to_jsonb</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">jsonb</code>
</p>
<p>
Converts an <code class="type">hstore</code> to a <code class="type">jsonb</code> value,
converting all non-null values to JSON strings.
</p>
<p>
This function is used implicitly when an <code class="type">hstore</code> value is
cast to <code class="type">jsonb</code>.
</p>
<p>
<code class="literal">hstore_to_jsonb('"a key"=>1, b=>t, c=>null, d=>12345, e=>012345, f=>1.234, g=>2.345e+4')</code>
→ <code class="returnvalue">{"a key": "1", "b": "t", "c": null, "d": "12345", "e": "012345", "f": "1.234", "g": "2.345e+4"}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.13.1.1.1" class="indexterm"></a>
<code class="function">hstore_to_json_loose</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">json</code>
</p>
<p>
Converts an <code class="type">hstore</code> to a <code class="type">json</code> value, but
attempts to distinguish numerical and Boolean values so they are
unquoted in the JSON.
</p>
<p>
<code class="literal">hstore_to_json_loose('"a key"=>1, b=>t, c=>null, d=>12345, e=>012345, f=>1.234, g=>2.345e+4')</code>
→ <code class="returnvalue">{"a key": 1, "b": true, "c": null, "d": 12345, "e": "012345", "f": 1.234, "g": 2.345e+4}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.14.1.1.1" class="indexterm"></a>
<code class="function">hstore_to_jsonb_loose</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">jsonb</code>
</p>
<p>
Converts an <code class="type">hstore</code> to a <code class="type">jsonb</code> value, but
attempts to distinguish numerical and Boolean values so they are
unquoted in the JSON.
</p>
<p>
<code class="literal">hstore_to_jsonb_loose('"a key"=>1, b=>t, c=>null, d=>12345, e=>012345, f=>1.234, g=>2.345e+4')</code>
→ <code class="returnvalue">{"a key": 1, "b": true, "c": null, "d": 12345, "e": "012345", "f": 1.234, "g": 2.345e+4}</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.15.1.1.1" class="indexterm"></a>
<code class="function">slice</code> ( <code class="type">hstore</code>, <code class="type">text[]</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Extracts a subset of an <code class="type">hstore</code> containing only the
specified keys.
</p>
<p>
<code class="literal">slice('a=>1,b=>2,c=>3'::hstore, ARRAY['b','c','x'])</code>
→ <code class="returnvalue">"b"=>"2", "c"=>"3"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.16.1.1.1" class="indexterm"></a>
<code class="function">each</code> ( <code class="type">hstore</code> )
→ <code class="returnvalue">setof record</code>
( <em class="parameter"><code>key</code></em> <code class="type">text</code>,
<em class="parameter"><code>value</code></em> <code class="type">text</code> )
</p>
<p>
Extracts an <code class="type">hstore</code>'s keys and values as a set of records.
</p>
<p>
<code class="literal">select * from each('a=>1,b=>2')</code>
→ <code class="returnvalue"></code>
</p><pre class="programlisting">
key | value
-----+-------
a | 1
b | 2
</pre><p>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.17.1.1.1" class="indexterm"></a>
<code class="function">exist</code> ( <code class="type">hstore</code>, <code class="type">text</code> )
→ <code class="returnvalue">boolean</code>
</p>
<p>
Does <code class="type">hstore</code> contain key?
</p>
<p>
<code class="literal">exist('a=>1', 'a')</code>
→ <code class="returnvalue">t</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.18.1.1.1" class="indexterm"></a>
<code class="function">defined</code> ( <code class="type">hstore</code>, <code class="type">text</code> )
→ <code class="returnvalue">boolean</code>
</p>
<p>
Does <code class="type">hstore</code> contain a non-<code class="literal">NULL</code> value
for key?
</p>
<p>
<code class="literal">defined('a=>NULL', 'a')</code>
→ <code class="returnvalue">f</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.19.1.1.1" class="indexterm"></a>
<code class="function">delete</code> ( <code class="type">hstore</code>, <code class="type">text</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Deletes pair with matching key.
</p>
<p>
<code class="literal">delete('a=>1,b=>2', 'b')</code>
→ <code class="returnvalue">"a"=>"1"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">delete</code> ( <code class="type">hstore</code>, <code class="type">text[]</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Deletes pairs with matching keys.
</p>
<p>
<code class="literal">delete('a=>1,b=>2,c=>3', ARRAY['a','b'])</code>
→ <code class="returnvalue">"c"=>"3"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<code class="function">delete</code> ( <code class="type">hstore</code>, <code class="type">hstore</code> )
→ <code class="returnvalue">hstore</code>
</p>
<p>
Deletes pairs matching those in the second argument.
</p>
<p>
<code class="literal">delete('a=>1,b=>2', 'a=>4,b=>2'::hstore)</code>
→ <code class="returnvalue">"a"=>"1"</code>
</p></td></tr><tr><td class="func_table_entry"><p class="func_signature">
<a id="id-1.11.7.28.6.4.2.2.22.1.1.1" class="indexterm"></a>
<code class="function">populate_record</code> ( <code class="type">anyelement</code>, <code class="type">hstore</code> )
→ <code class="returnvalue">anyelement</code>
</p>
<p>
Replaces fields in the left operand (which must be a composite type)
with matching values from <code class="type">hstore</code>.
</p>
<p>
<code class="literal">populate_record(ROW(1,2), 'f1=>42'::hstore)</code>
→ <code class="returnvalue">(42,2)</code>
</p></td></tr></tbody></table></div></div><br class="table-break" /><p>
In addition to these operators and functions, values of
the <code class="type">hstore</code> type can be subscripted, allowing them to act
like associative arrays. Only a single subscript of type <code class="type">text</code>
can be specified; it is interpreted as a key and the corresponding
value is fetched or stored. For example,
</p><pre class="programlisting">
CREATE TABLE mytable (h hstore);
INSERT INTO mytable VALUES ('a=>b, c=>d');
SELECT h['a'] FROM mytable;
h
---
b
(1 row)
UPDATE mytable SET h['c'] = 'new';
SELECT h FROM mytable;
h
----------------------
"a"=>"b", "c"=>"new"
(1 row)
</pre><p>
A subscripted fetch returns <code class="literal">NULL</code> if the subscript
is <code class="literal">NULL</code> or that key does not exist in
the <code class="type">hstore</code>. (Thus, a subscripted fetch is not greatly
different from the <code class="literal">-></code> operator.)
A subscripted update fails if the subscript is <code class="literal">NULL</code>;
otherwise, it replaces the value for that key, adding an entry to
the <code class="type">hstore</code> if the key does not already exist.
</p></div><div class="sect2" id="HSTORE-INDEXES"><div class="titlepage"><div><div><h3 class="title">F.18.3. Indexes <a href="#HSTORE-INDEXES" class="id_link">#</a></h3></div></div></div><p>
<code class="type">hstore</code> has GiST and GIN index support for the <code class="literal">@></code>,
<code class="literal">?</code>, <code class="literal">?&</code> and <code class="literal">?|</code> operators. For example:
</p><pre class="programlisting">
CREATE INDEX hidx ON testhstore USING GIST (h);
CREATE INDEX hidx ON testhstore USING GIN (h);
</pre><p>
<code class="literal">gist_hstore_ops</code> GiST opclass approximates a set of
key/value pairs as a bitmap signature. Its optional integer parameter
<code class="literal">siglen</code> determines the
signature length in bytes. The default length is 16 bytes.
Valid values of signature length are between 1 and 2024 bytes. 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 a signature length of 32 bytes:
</p><pre class="programlisting">
CREATE INDEX hidx ON testhstore USING GIST (h gist_hstore_ops(siglen=32));
</pre><p>
</p><p>
<code class="type">hstore</code> also supports <code class="type">btree</code> or <code class="type">hash</code> indexes for
the <code class="literal">=</code> operator. This allows <code class="type">hstore</code> columns to be
declared <code class="literal">UNIQUE</code>, or to be used in <code class="literal">GROUP BY</code>,
<code class="literal">ORDER BY</code> or <code class="literal">DISTINCT</code> expressions. The sort ordering
for <code class="type">hstore</code> values is not particularly useful, but these indexes
may be useful for equivalence lookups. Create indexes for <code class="literal">=</code>
comparisons as follows:
</p><pre class="programlisting">
CREATE INDEX hidx ON testhstore USING BTREE (h);
CREATE INDEX hidx ON testhstore USING HASH (h);
</pre></div><div class="sect2" id="HSTORE-EXAMPLES"><div class="titlepage"><div><div><h3 class="title">F.18.4. Examples <a href="#HSTORE-EXAMPLES" class="id_link">#</a></h3></div></div></div><p>
Add a key, or update an existing key with a new value:
</p><pre class="programlisting">
UPDATE tab SET h['c'] = '3';
</pre><p>
Another way to do the same thing is:
</p><pre class="programlisting">
UPDATE tab SET h = h || hstore('c', '3');
</pre><p>
If multiple keys are to be added or changed in one operation,
the concatenation approach is more efficient than subscripting:
</p><pre class="programlisting">
UPDATE tab SET h = h || hstore(array['q', 'w'], array['11', '12']);
</pre><p>
</p><p>
Delete a key:
</p><pre class="programlisting">
UPDATE tab SET h = delete(h, 'k1');
</pre><p>
</p><p>
Convert a <code class="type">record</code> to an <code class="type">hstore</code>:
</p><pre class="programlisting">
CREATE TABLE test (col1 integer, col2 text, col3 text);
INSERT INTO test VALUES (123, 'foo', 'bar');
SELECT hstore(t) FROM test AS t;
hstore
---------------------------------------------
"col1"=>"123", "col2"=>"foo", "col3"=>"bar"
(1 row)
</pre><p>
</p><p>
Convert an <code class="type">hstore</code> to a predefined <code class="type">record</code> type:
</p><pre class="programlisting">
CREATE TABLE test (col1 integer, col2 text, col3 text);
SELECT * FROM populate_record(null::test,
'"col1"=>"456", "col2"=>"zzz"');
col1 | col2 | col3
------+------+------
456 | zzz |
(1 row)
</pre><p>
</p><p>
Modify an existing record using the values from an <code class="type">hstore</code>:
</p><pre class="programlisting">
CREATE TABLE test (col1 integer, col2 text, col3 text);
INSERT INTO test VALUES (123, 'foo', 'bar');
SELECT (r).* FROM (SELECT t #= '"col3"=>"baz"' AS r FROM test t) s;
col1 | col2 | col3
------+------+------
123 | foo | baz
(1 row)
</pre><p>
</p></div><div class="sect2" id="HSTORE-STATISTICS"><div class="titlepage"><div><div><h3 class="title">F.18.5. Statistics <a href="#HSTORE-STATISTICS" class="id_link">#</a></h3></div></div></div><p>
The <code class="type">hstore</code> type, because of its intrinsic liberality, could
contain a lot of different keys. Checking for valid keys is the task of the
application. The following examples demonstrate several techniques for
checking keys and obtaining statistics.
</p><p>
Simple example:
</p><pre class="programlisting">
SELECT * FROM each('aaa=>bq, b=>NULL, ""=>1');
</pre><p>
</p><p>
Using a table:
</p><pre class="programlisting">
CREATE TABLE stat AS SELECT (each(h)).key, (each(h)).value FROM testhstore;
</pre><p>
</p><p>
Online statistics:
</p><pre class="programlisting">
SELECT key, count(*) FROM
(SELECT (each(h)).key FROM testhstore) AS stat
GROUP BY key
ORDER BY count DESC, key;
key | count
-----------+-------
line | 883
query | 207
pos | 203
node | 202
space | 197
status | 195
public | 194
title | 190
org | 189
...................
</pre><p>
</p></div><div class="sect2" id="HSTORE-COMPATIBILITY"><div class="titlepage"><div><div><h3 class="title">F.18.6. Compatibility <a href="#HSTORE-COMPATIBILITY" class="id_link">#</a></h3></div></div></div><p>
As of PostgreSQL 9.0, <code class="type">hstore</code> uses a different internal
representation than previous versions. This presents no obstacle for
dump/restore upgrades since the text representation (used in the dump) is
unchanged.
</p><p>
In the event of a binary upgrade, upward compatibility is maintained by
having the new code recognize old-format data. This will entail a slight
performance penalty when processing data that has not yet been modified by
the new code. It is possible to force an upgrade of all values in a table
column by doing an <code class="literal">UPDATE</code> statement as follows:
</p><pre class="programlisting">
UPDATE tablename SET hstorecol = hstorecol || '';
</pre><p>
</p><p>
Another way to do it is:
</p><pre class="programlisting">
ALTER TABLE tablename ALTER hstorecol TYPE hstore USING hstorecol || '';
</pre><p>
The <code class="command">ALTER TABLE</code> method requires an
<code class="literal">ACCESS EXCLUSIVE</code> lock on the table,
but does not result in bloating the table with old row versions.
</p></div><div class="sect2" id="HSTORE-TRANSFORMS"><div class="titlepage"><div><div><h3 class="title">F.18.7. Transforms <a href="#HSTORE-TRANSFORMS" class="id_link">#</a></h3></div></div></div><p>
Additional extensions are available that implement transforms for
the <code class="type">hstore</code> type for the languages PL/Perl and PL/Python. The
extensions for PL/Perl are called <code class="literal">hstore_plperl</code>
and <code class="literal">hstore_plperlu</code>, for trusted and untrusted PL/Perl.
If you install these transforms and specify them when creating a
function, <code class="type">hstore</code> values are mapped to Perl hashes. The
extension for PL/Python is called <code class="literal">hstore_plpython3u</code>.
If you use it, <code class="type">hstore</code> values are mapped to Python dictionaries.
</p><div class="caution"><h3 class="title">Caution</h3><p>
It is strongly recommended that the transform extensions be installed in
the same schema as <code class="filename">hstore</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="HSTORE-AUTHORS"><div class="titlepage"><div><div><h3 class="title">F.18.8. Authors <a href="#HSTORE-AUTHORS" class="id_link">#</a></h3></div></div></div><p>
Oleg Bartunov <code class="email"><<a class="email" href="mailto:oleg@sai.msu.su">oleg@sai.msu.su</a>></code>, Moscow, Moscow University, Russia
</p><p>
Teodor Sigaev <code class="email"><<a class="email" href="mailto:teodor@sigaev.ru">teodor@sigaev.ru</a>></code>, Moscow, Delta-Soft Ltd., Russia
</p><p>
Additional enhancements by Andrew Gierth <code class="email"><<a class="email" href="mailto:andrew@tao11.riddles.org.uk">andrew@tao11.riddles.org.uk</a>></code>,
United Kingdom
</p></div></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="fuzzystrmatch.html" title="F.17. fuzzystrmatch — determine string similarities and distance">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. Additional Supplied Modules and Extensions">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="intagg.html" title="F.19. intagg — integer aggregator and enumerator">Next</a></td></tr><tr><td width="40%" align="left" valign="top">F.17. fuzzystrmatch — determine string similarities and distance </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 16.2 Documentation">Home</a></td><td width="40%" align="right" valign="top"> F.19. intagg — integer aggregator and enumerator</td></tr></table></div></body></html>
|
