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array_offset() and array_offsets()

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These functions return the offset position or positions of a value in an
array.

Author: Pavel Stěhule
Reviewed by: Jim Nasby
This commit is contained in:
Alvaro Herrera
2015-03-18 16:01:34 -03:00
parent f9dead5624
commit 13dbc7a824
10 changed files with 525 additions and 8 deletions
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19
doc/src/sgml/array.sgml
View File

@@ -600,6 +600,25 @@ SELECT * FROM sal_emp WHERE pay_by_quarter && ARRAY[10000];
index, as described in <xref linkend="indexes-types">.
</para>
<para>
You can also search for specific values in an array using the <function>array_offset</>
and <function>array_offsets</> functions. The former returns the position of
the first occurrence of a value in an array; the latter returns an array with the
positions of all occurrences of the value in the array. For example:
<programlisting>
SELECT array_offset(ARRAY['sun','mon','tue','wed','thu','fri','sat'], 'mon');
array_offset
--------------
2
SELECT array_offsets(ARRAY[1, 4, 3, 1, 3, 4, 2, 1], 1);
array_offsets
---------------
{1,4,8}
</programlisting>
</para>
<tip>
<para>
Arrays are not sets; searching for specific array elements

49
doc/src/sgml/func.sgml
View File

@@ -11479,6 +11479,12 @@ SELECT NULLIF(value, '(none)') ...
<indexterm>
<primary>array_lower</primary>
</indexterm>
<indexterm>
<primary>array_offset</primary>
</indexterm>
<indexterm>
<primary>array_offsets</primary>
</indexterm>
<indexterm>
<primary>array_prepend</primary>
</indexterm>
@@ -11596,6 +11602,32 @@ SELECT NULLIF(value, '(none)') ...
<entry><literal>array_lower('[0:2]={1,2,3}'::int[], 1)</literal></entry>
<entry><literal>0</literal></entry>
</row>
<row>
<entry>
<literal>
<function>array_offset</function>(<type>anyarray</type>, <type>anyelement</type> <optional>, <type>int</type></optional>)
</literal>
</entry>
<entry><type>int</type></entry>
<entry>returns the offset of the first occurrence of the second
argument in the array, starting at the element indicated by the third
argument or at the first element (array must be one-dimensional)</entry>
<entry><literal>array_offset(ARRAY['sun','mon','tue','wed','thu','fri','sat'], 'mon')</literal></entry>
<entry><literal>2</literal></entry>
</row>
<row>
<entry>
<literal>
<function>array_offsets</function>(<type>anyarray</type>, <type>anyelement</type>)
</literal>
</entry>
<entry><type>int[]</type></entry>
<entry>returns an array of offsets of all occurrences of the second
argument in the array given as first argument (array must be
one-dimensional)</entry>
<entry><literal>array_offsets(ARRAY['A','A','B','A'], 'A')</literal></entry>
<entry><literal>{1,2,4}</literal></entry>
</row>
<row>
<entry>
<literal>
@@ -11707,6 +11739,23 @@ NULL baz</literallayout>(3 rows)</entry>
</tgroup>
</table>
<para>
In <function>array_offset</function> and <function>array_offsets</>,
each array element is compared to the searched value using
<literal>IS NOT DISTINCT FROM</literal> semantics.
</para>
<para>
In <function>array_offset</function>, <literal>NULL</literal> is returned
if the value is not found.
</para>
<para>
In <function>array_offsets</function>, <literal>NULL</literal> is returned
only if the array is <literal>NULL</literal>; if the value is not found in
the array, an empty array is returned instead.
</para>
<para>
In <function>string_to_array</function>, if the delimiter parameter is
NULL, each character in the input string will become a separate element in