Add docs for any_value aggregation function

docs/src/main/sphinx/functions/aggregate.rst

@@ -93,9 +93,30 @@ Using a filter you retain all information::
 General aggregate functions
 ---------------------------
 
+.. function:: any_value(x) -> [same as input]
+
+    Returns an arbitrary non-null value ``x``, if one exists. ``x`` can be any
+    valid expression. This allows you to return values from columns that are not
+    directly part of the aggregation, inluding expressions using these columns,
+    in a query.
+
+    For example, the following query returns the customer name from the ``name``
+    column, and returns the sum of all total prices as customer spend. The
+    aggregation however uses the rows grouped by the customer identifier
+    ``custkey`` a required, since only that column is guaranteed to be unique::
+
+        SELECT sum(o.totalprice) as spend,
+            any_value(c.name)
+        FROM tpch.tiny.orders o
+        JOIN tpch.tiny.customer c
+        ON o.custkey  = c.custkey
+        GROUP BY c.custkey;
+        ORDER BY spend;
+
 .. function:: arbitrary(x) -> [same as input]
 
-    Returns an arbitrary non-null value of ``x``, if one exists.
+    Returns an arbitrary non-null value of ``x``, if one exists. Identical to
+    :func:`any_value`.
 
 .. function:: array_agg(x) -> array<[same as input]>
 

docs/src/main/sphinx/functions/list-by-topic.rst

@@ -7,6 +7,7 @@ Aggregate
 
 For more details, see :doc:`aggregate`
 
+* :func:`any_value`
 * :func:`approx_distinct`
 * :func:`approx_most_frequent`
 * :func:`approx_percentile`

docs/src/main/sphinx/functions/list.rst

@@ -31,6 +31,7 @@ A
 - :ref:`AND <logical-operators>`
 - :ref:`ANY <quantified-comparison-predicates>`
 - :func:`any_match`
+- :func:`any_value`
 - :func:`approx_distinct`
 - :func:`approx_most_frequent`
 - :func:`approx_percentile`