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    <h3>ARRAYs can only hold elements of the same type</h3> <p>Your example displays a <code>text</code> and an <code>integer</code> value (no single quotes around <code>1</code>). It is generally impossible to mix types in an array. To get those values into an array you have to create a <code>composite type</code> and then form an ARRAY of that composite type like you already mentioned yourself.</p> <p><strong><em>Alternatively</em></strong> you can use the data types <a href="https://www.postgresql.org/docs/current/static/datatype-json.html" rel="nofollow"><code>json</code></a> in Postgres 9.2+, <code>jsonb</code> in Postgres 9.4+ or <a href="http://www.postgresql.org/docs/current/interactive/hstore.html" rel="nofollow"><code>hstore</code></a> for key-value pairs.</p> <hr> <p>Of course, you can cast the <code>integer</code> to <code>text</code>, and work with a two-dimensional text array. Consider the two syntax variants for a array input in the demo below and consult <a href="http://www.postgresql.org/docs/current/interactive/arrays.html#ARRAYS-INPUT" rel="nofollow">the manual on array input</a>.</p> <p>There is a limitation to overcome. If you try to aggregate an ARRAY (build from key and value) into a two-dimensional array, the aggregate function <code>array_agg()</code> or the <code>ARRAY</code> constructor error out:</p> <pre><code>ERROR: could not find array type for data type text[] </code></pre> <p>There are ways around it, though.</p> <h3>Aggregate key-value pairs into a 2-dimensional array</h3> <p>PostgreSQL 9.1 with <a href="http://www.postgresql.org/docs/current/interactive/runtime-config-compatible.html#GUC-STANDARD-CONFORMING-STRINGS" rel="nofollow"><code>standard_conforming_strings= on</code></a>:</p> <pre><code>CREATE TEMP TABLE tbl( id int ,txt text ,txtarr text[] ); </code></pre> <p>The column <code>txtarr</code> is just there to demonstrate syntax variants in the INSERT command. The third row is spiked with meta-characters:</p> <pre><code>INSERT INTO tbl VALUES (1, 'foo', '{{1,foo1},{2,bar1},{3,baz1}}') ,(2, 'bar', ARRAY[['1','foo2'],['2','bar2'],['3','baz2']]) ,(3, '}b",a{r''', '{{1,foo3},{2,bar3},{3,baz3}}'); -- txt has meta-characters SELECT * FROM tbl; </code></pre> <p>Simple case: aggregate two integer (I use the same twice) into a two-dimensional int array:</p> <h3>Update: Better with custom aggregate function</h3> <p>With the <a href="http://www.postgresql.org/docs/9.1/static/extend-type-system.html#EXTEND-TYPES-POLYMORPHIC" rel="nofollow">polymorphic type <code>anyarray</code></a> it works for all base types:</p> <pre><code>CREATE AGGREGATE array_agg_mult (anyarray) ( SFUNC = array_cat ,STYPE = anyarray ,INITCOND = '{}' ); </code></pre> <p>Call:</p> <pre><code>SELECT array_agg_mult(ARRAY[ARRAY[id,id]]) AS x -- for int ,array_agg_mult(ARRAY[ARRAY[id::text,txt]]) AS y -- or text FROM tbl; </code></pre> <p>Note the additional <code>ARRAY[]</code> layer to make it a multidimensional array.</p> <h3>Update for Postgres 9.5+</h3> <p>Postgres now ships a variant of <code>array_agg()</code> accepting array input and you can replace my custom function from above with this:</p> <p><a href="https://www.postgresql.org/docs/current/static/functions-aggregate.html" rel="nofollow">The manual:</a></p> <blockquote> <p><code>array_agg(expression)</code><br> ...<br> input arrays concatenated into array of one higher dimension (inputs must all have same dimensionality, and cannot be empty or NULL)</p> </blockquote>
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