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<title>6.17. Array Functions and Operators — Presto 0.161 Documentation</title>
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<div class="header">
<h1 class="heading"><a href="../index.html">
<span>Presto 0.161 Documentation</span></a></h1>
<h2 class="heading"><span>6.17. Array Functions and Operators</span></h2>
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<div class="section" id="array-functions-and-operators">
<h1>6.17. Array 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 access an element of an array and is indexed starting from one:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">my_array</span><span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="k">AS</span> <span class="n">first_element</span>
</pre></div>
</div>
</div>
<div class="section" id="concatenation-operator">
<h2>Concatenation Operator: ||</h2>
<p>The <code class="docutils literal"><span class="pre">||</span></code> operator is used to concatenate an array with an array or an element of the same type:</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">||</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">2</span><span class="p">];</span> <span class="c1">-- [1, 2]</span>
<span class="k">SELECT</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">1</span><span class="p">]</span> <span class="o">||</span> <span class="mi">2</span><span class="p">;</span> <span class="c1">-- [1, 2]</span>
<span class="k">SELECT</span> <span class="mi">2</span> <span class="o">||</span> <span class="nb">ARRAY</span> <span class="p">[</span><span class="mi">1</span><span class="p">];</span> <span class="c1">-- [2, 1]</span>
</pre></div>
</div>
</div>
<div class="section" id="array-functions">
<h2>Array Functions</h2>
<dl class="function">
<dt id="array_distinct">
<code class="descname">array_distinct</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Remove duplicate values from the array <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
<dl class="function">
<dt id="array_intersect">
<code class="descname">array_intersect</code><span class="sig-paren">(</span><em>x</em>, <em>y</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Returns an array of the elements in the intersection of <code class="docutils literal"><span class="pre">x</span></code> and <code class="docutils literal"><span class="pre">y</span></code>, without duplicates.</p>
</dd></dl>
<dl class="function">
<dt id="array_union">
<code class="descname">array_union</code><span class="sig-paren">(</span><em>x</em>, <em>y</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Returns an array of the elements in the union of <code class="docutils literal"><span class="pre">x</span></code> and <code class="docutils literal"><span class="pre">y</span></code>, without duplicates.</p>
</dd></dl>
<dl class="function">
<dt id="array_join">
<code class="descname">array_join</code><span class="sig-paren">(</span><em>x</em>, <em>delimiter</em>, <em>null_replacement</em><span class="sig-paren">)</span> → varchar</dt>
<dd><p>Concatenates the elements of the given array using the delimiter and an optional string to replace nulls.</p>
</dd></dl>
<dl class="function">
<dt id="array_max">
<code class="descname">array_max</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → x</dt>
<dd><p>Returns the maximum value of input array.</p>
</dd></dl>
<dl class="function">
<dt id="array_min">
<code class="descname">array_min</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → x</dt>
<dd><p>Returns the minimum value of input array.</p>
</dd></dl>
<dl class="function">
<dt id="array_position">
<code class="descname">array_position</code><span class="sig-paren">(</span><em>x</em>, <em>element</em><span class="sig-paren">)</span> → bigint</dt>
<dd><p>Returns the position of the first occurrence of the <code class="docutils literal"><span class="pre">element</span></code> in array <code class="docutils literal"><span class="pre">x</span></code> (or 0 if not found).</p>
</dd></dl>
<dl class="function">
<dt id="array_remove">
<code class="descname">array_remove</code><span class="sig-paren">(</span><em>x</em>, <em>element</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Remove all elements that equal <code class="docutils literal"><span class="pre">element</span></code> from array <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
<dl class="function">
<dt id="array_sort">
<code class="descname">array_sort</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Sorts and returns the array <code class="docutils literal"><span class="pre">x</span></code>. The elements of <code class="docutils literal"><span class="pre">x</span></code> must be orderable.
Null elements will be placed at the end of the returned array.</p>
</dd></dl>
<dl class="function">
<dt id="cardinality">
<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 array <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">concat</code><span class="sig-paren">(</span><em>x</em>, <em>y</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Concatenates the arrays <code class="docutils literal"><span class="pre">x</span></code> and <code class="docutils literal"><span class="pre">y</span></code>. This function provides the same
functionality as the SQL-standard concatenation operator (<code class="docutils literal"><span class="pre">||</span></code>).</p>
</dd></dl>
<dl class="function">
<dt id="contains">
<code class="descname">contains</code><span class="sig-paren">(</span><em>x</em>, <em>element</em><span class="sig-paren">)</span> → boolean</dt>
<dd><p>Returns true if the array <code class="docutils literal"><span class="pre">x</span></code> contains the <code class="docutils literal"><span class="pre">element</span></code>.</p>
</dd></dl>
<dl class="function">
<dt id="element_at">
<code class="descname">element_at</code><span class="sig-paren">(</span><em>array<E></em>, <em>index</em><span class="sig-paren">)</span> → E</dt>
<dd><p>Returns element of <code class="docutils literal"><span class="pre">array</span></code> at given <code class="docutils literal"><span class="pre">index</span></code>.
If <code class="docutils literal"><span class="pre">index</span></code> >= 0, this function provides the same functionality as the SQL-standard subscript operator (<code class="docutils literal"><span class="pre">[]</span></code>).
If <code class="docutils literal"><span class="pre">index</span></code> < 0, <code class="docutils literal"><span class="pre">element_at</span></code> accesses elements from the last to the first.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">filter</code><span class="sig-paren">(</span><em>array</em>, <em>function</em><span class="sig-paren">)</span> → array</dt>
<dd><p>See <a class="reference internal" href="lambda.html#filter" title="filter"><code class="xref py py-func docutils literal"><span class="pre">filter()</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt id="flatten">
<code class="descname">flatten</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Flattens an <code class="docutils literal"><span class="pre">array(array(T))</span></code> to an <code class="docutils literal"><span class="pre">array(T)</span></code> by concatenating the contained arrays.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">reduce</code><span class="sig-paren">(</span><em>array</em>, <em>initialState</em>, <em>inputFunction</em>, <em>outputFunction</em><span class="sig-paren">)</span> → x</dt>
<dd><p>See <a class="reference internal" href="lambda.html#reduce" title="reduce"><code class="xref py py-func docutils literal"><span class="pre">reduce()</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">reverse</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Returns an array which has the reversed order of array <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
<dl class="function">
<dt id="sequence">
<code class="descname">sequence</code><span class="sig-paren">(</span><em>start</em>, <em>stop</em><span class="sig-paren">)</span> → array<bigint></dt>
<dd><p>Generate a sequence of integers from <code class="docutils literal"><span class="pre">start</span></code> to <code class="docutils literal"><span class="pre">stop</span></code>, incrementing
by <code class="docutils literal"><span class="pre">1</span></code> if <code class="docutils literal"><span class="pre">start</span></code> is less than or equal to <code class="docutils literal"><span class="pre">stop</span></code>, otherwise <code class="docutils literal"><span class="pre">-1</span></code>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">sequence</code><span class="sig-paren">(</span><em>start</em>, <em>stop</em>, <em>step</em><span class="sig-paren">)</span> → array<bigint></dt>
<dd><p>Generate a sequence of integers from <code class="docutils literal"><span class="pre">start</span></code> to <code class="docutils literal"><span class="pre">stop</span></code>, incrementing by <code class="docutils literal"><span class="pre">step</span></code>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">sequence</code><span class="sig-paren">(</span><em>start</em>, <em>stop</em>, <em>step</em><span class="sig-paren">)</span> → array<timestamp></dt>
<dd><p>Generate a sequence of timestamps from <code class="docutils literal"><span class="pre">start</span></code> to <code class="docutils literal"><span class="pre">stop</span></code>, incrementing by <code class="docutils literal"><span class="pre">step</span></code>.
The type of <code class="docutils literal"><span class="pre">step</span></code> can be either <code class="docutils literal"><span class="pre">INTERVAL</span> <span class="pre">DAY</span> <span class="pre">TO</span> <span class="pre">SECOND</span></code> or <code class="docutils literal"><span class="pre">INTERVAL</span> <span class="pre">YEAR</span> <span class="pre">TO</span> <span class="pre">MONTH</span></code>.</p>
</dd></dl>
<dl class="function">
<dt id="shuffle">
<code class="descname">shuffle</code><span class="sig-paren">(</span><em>x</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Generate a random permutation of the given array <code class="docutils literal"><span class="pre">x</span></code>.</p>
</dd></dl>
<dl class="function">
<dt id="slice">
<code class="descname">slice</code><span class="sig-paren">(</span><em>x</em>, <em>start</em>, <em>length</em><span class="sig-paren">)</span> → array</dt>
<dd><p>Subsets array <code class="docutils literal"><span class="pre">x</span></code> starting from index <code class="docutils literal"><span class="pre">start</span></code> (or starting from the end
if <code class="docutils literal"><span class="pre">start</span></code> is negative) with a length of <code class="docutils literal"><span class="pre">length</span></code>.</p>
</dd></dl>
<dl class="function">
<dt>
<code class="descname">transform</code><span class="sig-paren">(</span><em>array</em>, <em>function</em><span class="sig-paren">)</span> → array</dt>
<dd><p>See <a class="reference internal" href="lambda.html#transform" title="transform"><code class="xref py py-func docutils literal"><span class="pre">transform()</span></code></a>.</p>
</dd></dl>
<dl class="function">
<dt id="zip">
<code class="descname">zip</code><span class="sig-paren">(</span><em>array1</em>, <em>array2</em><span class="optional">[</span>, <em>...</em><span class="optional">]</span><span class="sig-paren">)</span> → array<row></dt>
<dd><p>Merges the given arrays, element-wise, into a single array of rows. The M-th element of
the N-th argument will be the N-th field of the M-th output element.
If the arguments have an uneven length, missing values are filled with <code class="docutils literal"><span class="pre">NULL</span></code>.</p>
<div class="highlight-sql"><div class="highlight"><pre><span></span><span class="k">SELECT</span> <span class="n">zip</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">'1b'</span><span class="p">,</span> <span class="k">null</span><span class="p">,</span> <span class="s1">'3b'</span><span class="p">]);</span> <span class="c1">-- [ROW(1, '1b'), ROW(2, null), ROW(null, '3b')]</span>
</pre></div>
</div>
</dd></dl>
</div>
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