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<?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.16. hstore</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 V1.79.1" /><link rel="prev" href="fuzzystrmatch.html" title="F.15. fuzzystrmatch" /><link rel="next" href="intagg.html" title="F.17. intagg" /></head><body id="docContent" class="container-fluid col-10"><div xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">F.16. hstore</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="fuzzystrmatch.html" title="F.15. fuzzystrmatch">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 13.1 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="intagg.html" title="F.17. intagg">Next</a></td></tr></table><hr></hr></div><div class="sect1" id="HSTORE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">F.16. hstore</h2></div></div></div><div class="toc"><dl class="toc"><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.5">F.16.1. <code class="type">hstore</code> External Representation</a></span></dt><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.6">F.16.2. <code class="type">hstore</code> Operators and Functions</a></span></dt><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.7">F.16.3. Indexes</a></span></dt><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.8">F.16.4. Examples</a></span></dt><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.9">F.16.5. Statistics</a></span></dt><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.10">F.16.6. Compatibility</a></span></dt><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.11">F.16.7. Transforms</a></span></dt><dt><span class="sect2"><a href="hstore.html#id-1.11.7.25.12">F.16.8. Authors</a></span></dt></dl></div><a id="id-1.11.7.25.2" 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="id-1.11.7.25.5"><div class="titlepage"><div><div><h3 class="title">F.16.1. <code class="type">hstore</code> External Representation</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="id-1.11.7.25.6"><div class="titlepage"><div><div><h3 class="title">F.16.2. <code class="type">hstore</code> Operators and Functions</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="note"><h3 class="title">Note</h3><p> Prior to PostgreSQL 8.2, the containment operators <code class="literal">@></code> and <code class="literal"><@</code> were called <code class="literal">@</code> and <code class="literal">~</code>, respectively. These names are still available, but are deprecated and will eventually be removed. Notice that the old names are reversed from the convention formerly followed by the core geometric data types! </p></div><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-1.11.7.25.6.5.2.2.1.1.1.1" 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-1.11.7.25.6.5.2.2.5.1.1.1" 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-1.11.7.25.6.5.2.2.6.1.1.1" 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-1.11.7.25.6.5.2.2.7.1.1.1" 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-1.11.7.25.6.5.2.2.8.1.1.1" 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-1.11.7.25.6.5.2.2.9.1.1.1" 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-1.11.7.25.6.5.2.2.10.1.1.1" 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-1.11.7.25.6.5.2.2.11.1.1.1" 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-1.11.7.25.6.5.2.2.12.1.1.1" 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-1.11.7.25.6.5.2.2.13.1.1.1" 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-1.11.7.25.6.5.2.2.14.1.1.1" 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-1.11.7.25.6.5.2.2.15.1.1.1" 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-1.11.7.25.6.5.2.2.16.1.1.1" 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-1.11.7.25.6.5.2.2.17.1.1.1" 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-1.11.7.25.6.5.2.2.18.1.1.1" 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-1.11.7.25.6.5.2.2.19.1.1.1" 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-1.11.7.25.6.5.2.2.22.1.1.1" 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" /></div><div class="sect2" id="id-1.11.7.25.7"><div class="titlepage"><div><div><h3 class="title">F.16.3. Indexes</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="id-1.11.7.25.8"><div class="titlepage"><div><div><h3 class="title">F.16.4. Examples</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 = h || hstore('c', '3'); </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="id-1.11.7.25.9"><div class="titlepage"><div><div><h3 class="title">F.16.5. Statistics</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"> SELECT (each(h)).key, (each(h)).value INTO stat 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="id-1.11.7.25.10"><div class="titlepage"><div><div><h3 class="title">F.16.6. Compatibility</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 exclusive lock on the table, but does not result in bloating the table with old row versions. </p></div><div class="sect2" id="id-1.11.7.25.11"><div class="titlepage"><div><div><h3 class="title">F.16.7. Transforms</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 extensions for PL/Python are called <code class="literal">hstore_plpythonu</code>, <code class="literal">hstore_plpython2u</code>, and <code class="literal">hstore_plpython3u</code> (see <a class="xref" href="plpython-python23.html" title="45.1. Python 2 vs. Python 3">Section 45.1</a> for the PL/Python naming convention). If you use them, <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="id-1.11.7.25.12"><div class="titlepage"><div><div><h3 class="title">F.16.8. Authors</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 xmlns="http://www.w3.org/TR/xhtml1/transitional" class="navfooter"><hr></hr><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="fuzzystrmatch.html" title="F.15. fuzzystrmatch">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="contrib.html" title="Appendix F. 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