-
Notifications
You must be signed in to change notification settings - Fork 16
/
Copy pathmap.html
171 lines (146 loc) · 9.43 KB
/
map.html
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
<!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>6.18. Map Functions and Operators — Presto 0.184 Documentation</title>
<link rel="stylesheet" href="../_static/presto.css" type="text/css" />
<link rel="stylesheet" href="../_static/pygments.css" type="text/css" />
<script type="text/javascript">
var DOCUMENTATION_OPTIONS = {
URL_ROOT: '../',
VERSION: '0.184',
COLLAPSE_INDEX: false,
FILE_SUFFIX: '.html',
HAS_SOURCE: true
};
</script>
<script type="text/javascript" src="../_static/jquery.js"></script>
<script type="text/javascript" src="../_static/underscore.js"></script>
<script type="text/javascript" src="../_static/doctools.js"></script>
<link rel="index" title="Index" href="../genindex.html" />
<link rel="search" title="Search" href="../search.html" />
<link rel="top" title="Presto 0.184 Documentation" href="../index.html" />
<link rel="up" title="6. Functions and Operators" href="../functions.html" />
<link rel="next" title="6.19. Lambda Expressions and Functions" href="lambda.html" />
<link rel="prev" title="6.17. Array Functions and Operators" href="array.html" />
</head>
<body role="document">
<div class="header">
<h1 class="heading"><a href="../index.html">
<span>Presto 0.184 Documentation</span></a></h1>
<h2 class="heading"><span>6.18. Map Functions and Operators</span></h2>
</div>
<div class="topnav">
<p class="nav">
<span class="left">
« <a href="array.html">6.17. Array Functions and Operators</a>
</span>
<span class="right">
<a href="lambda.html">6.19. Lambda Expressions and Functions</a> »
</span>
</p>
</div>
<div class="content">
<div class="section" id="map-functions-and-operators">
<h1>6.18. Map Functions and Operators</h1>
<div class="section" id="subscript-operator">
<h2>Subscript Operator: []</h2>
<p>The <code class="docutils literal"><span class="pre">[]</span></code> operator is used to retrieve the value corresponding to a given key from a map:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">name_to_age_map</span><span class="p">[</span><span class="s1">'Bob'</span><span class="p">]</span> <span class="k">AS</span> <span class="n">bob_age</span><span class="p">;</span>
</pre></div>
</div>
</div>
<div class="section" id="map-functions">
<h2>Map Functions</h2>
<dl class="function">
<dt>
<code class="descname">cardinality</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → bigint</dt>
<dd><p>Returns the cardinality (size) of the map <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">element_at</code><span class="sig-paren">(</span><em>map<K</em>, <em>V></em>, <em>key</em><span class="sig-paren">)</span> → V</dt>
<dd><p>Returns value for given <code class="docutils literal"><span class="pre">key</span></code>, or <code class="docutils literal"><span class="pre">NULL</span></code> if the key is not contained in the map.</p>
</dd></dl>
<dl class="function">
<dt id="map">
<code class="descname">map</code><span class="sig-paren">(</span><span class="sig-paren">)</span> → map<unknown, unknown></dt>
<dd><p>Returns an empty map.</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="k">map</span><span class="p">();</span> <span class="c1">-- {}</span>
</pre></div>
</div>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">map</code><span class="sig-paren">(</span><em>array<K></em>, <em>array<V></em><span class="sig-paren">)</span> → map<K,V></dt>
<dd><p>Returns a map created using the given key/value arrays.</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="k">map</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span><span class="mi">3</span><span class="p">],</span> <span class="nb">ARRAY</span><span class="p">[</span><span class="mi">2</span><span class="p">,</span><span class="mi">4</span><span class="p">]);</span> <span class="c1">-- {1 -> 2, 3 -> 4}</span>
</pre></div>
</div>
<p>See also <a class="reference internal" href="aggregate.html#map_agg" title="map_agg"><code class="xref py py-func docutils literal"><span class="pre">map_agg()</span></code></a> and <a class="reference internal" href="aggregate.html#multimap_agg" title="multimap_agg"><code class="xref py py-func docutils literal"><span class="pre">multimap_agg()</span></code></a> for creating a map as an aggregation.</p>
</dd></dl>
<dl class="function">
<dt id="map_from_entries">
<code class="descname">map_from_entries</code><span class="sig-paren">(</span><em>array<row<K</em>, <em>V>></em><span class="sig-paren">)</span> → map<K,V></dt>
<dd><p>Returns a map created from the given array of entries.</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">map_from_entries</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">[(</span><span class="mi">1</span><span class="p">,</span> <span class="s1">'x'</span><span class="p">),</span> <span class="p">(</span><span class="mi">2</span><span class="p">,</span> <span class="s1">'y'</span><span class="p">)]);</span> <span class="c1">-- {1 -> 'x', 2 -> 'y'}</span>
</pre></div>
</div>
</dd></dl>
<dl class="function">
<dt id="map_entries">
<code class="descname">map_entries</code><span class="sig-paren">(</span><em>map<K</em>, <em>V></em><span class="sig-paren">)</span> → array<row<K,V>></dt>
<dd><p>Returns an array of all entries in the given map.</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">map_entries</span><span class="p">(</span><span class="k">MAP</span><span class="p">(</span><span class="nb">ARRAY</span><span class="p">[</span><span class="mi">1</span><span class="p">,</span> <span class="mi">2</span><span class="p">],</span> <span class="nb">ARRAY</span><span class="p">[</span><span class="s1">'x'</span><span class="p">,</span> <span class="s1">'y'</span><span class="p">]));</span> <span class="c1">-- [ROW(1, 'x'), ROW(2, 'y')]</span>
</pre></div>
</div>
</dd></dl>
<dl class="function">
<dt id="map_concat">
<code class="descname">map_concat</code><span class="sig-paren">(</span><em>map1<K</em>, <em>V></em>, <em>map2<K</em>, <em>V></em>, <em>...</em>, <em>mapN<K</em>, <em>V></em><span class="sig-paren">)</span> → map<K,V></dt>
<dd><p>Returns the union of all the given maps. If a key is found in multiple given maps,
that key’s value in the resulting map comes from the last one of those maps.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">map_filter</code><span class="sig-paren">(</span><em>map<K</em>, <em>V></em>, <em>function</em><span class="sig-paren">)</span> → map<K,V></dt>
<dd><p>See <a class="reference internal" href="lambda.html#map_filter" title="map_filter"><code class="xref py py-func docutils literal"><span class="pre">map_filter()</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">transform_keys</code><span class="sig-paren">(</span><em>map<K1</em>, <em>V></em>, <em>function</em><span class="sig-paren">)</span> → MAP<K2,V></dt>
<dd><p>See <a class="reference internal" href="lambda.html#transform_keys" title="transform_keys"><code class="xref py py-func docutils literal"><span class="pre">transform_keys()</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">transform_values</code><span class="sig-paren">(</span><em>map<K</em>, <em>V1></em>, <em>function</em><span class="sig-paren">)</span> → MAP<K,V2></dt>
<dd><p>See <a class="reference internal" href="lambda.html#transform_values" title="transform_values"><code class="xref py py-func docutils literal"><span class="pre">transform_values()</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt id="map_keys">
<code class="descname">map_keys</code><span class="sig-paren">(</span><em>x<K</em>, <em>V></em><span class="sig-paren">)</span> → array<K></dt>
<dd><p>Returns all the keys in the map <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
<dl class="function">
<dt id="map_values">
<code class="descname">map_values</code><span class="sig-paren">(</span><em>x<K</em>, <em>V></em><span class="sig-paren">)</span> → array<V></dt>
<dd><p>Returns all the values in the map <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
</div>
</div>
</div>
<div class="bottomnav">
<p class="nav">
<span class="left">
« <a href="array.html">6.17. Array Functions and Operators</a>
</span>
<span class="right">
<a href="lambda.html">6.19. Lambda Expressions and Functions</a> »
</span>
</p>
</div>
<div class="footer" role="contentinfo">
</div>
</body>
</html>