From 8a500bc61c7259de6101715d5b328deda077a543 Mon Sep 17 00:00:00 2001
From: Phillip Cloud <417981+cpcloud@users.noreply.github.com>
Date: Fri, 20 May 2022 10:15:59 -0700
Subject: [PATCH] feat(duckdb): implement arbitrary first and last aggregation

---
 ibis/backends/duckdb/registry.py        | 7 +++++++
 ibis/backends/tests/test_aggregation.py | 4 ++--
 2 files changed, 9 insertions(+), 2 deletions(-)

diff --git a/ibis/backends/duckdb/registry.py b/ibis/backends/duckdb/registry.py
index 1c892a0347a6..c53ccd5c1c46 100644
--- a/ibis/backends/duckdb/registry.py
+++ b/ibis/backends/duckdb/registry.py
@@ -159,6 +159,12 @@ def _strftime(t, expr):
     )
 
 
+def _arbitrary(t, expr):
+    if (how := expr.op().how) == "heavy":
+        raise ValueError(f"how={how!r} not supported in the DuckDB backend")
+    return t._reduction(getattr(sa.func, how), expr)
+
+
 operation_registry.update(
     {
         ops.ArrayColumn: _array_column,
@@ -187,6 +193,7 @@ def _strftime(t, expr):
         ),
         ops.HLLCardinality: reduction(sa.func.approx_count_distinct),
         ops.Strftime: _strftime,
+        ops.Arbitrary: _arbitrary,
     }
 )
 
diff --git a/ibis/backends/tests/test_aggregation.py b/ibis/backends/tests/test_aggregation.py
index fb810c23788c..ec6a7042df91 100644
--- a/ibis/backends/tests/test_aggregation.py
+++ b/ibis/backends/tests/test_aggregation.py
@@ -238,7 +238,7 @@ def test_aggregate_grouped(
             lambda t, where: t.double_col[where].iloc[0],
             id='arbitrary_first',
             marks=pytest.mark.notimpl(
-                ['impala', 'postgres', 'mysql', 'sqlite', 'duckdb']
+                ['impala', 'postgres', 'mysql', 'sqlite']
             ),
         ),
         param(
@@ -246,7 +246,7 @@ def test_aggregate_grouped(
             lambda t, where: t.double_col[where].iloc[-1],
             id='arbitrary_last',
             marks=pytest.mark.notimpl(
-                ['impala', 'postgres', 'mysql', 'sqlite', 'duckdb']
+                ['impala', 'postgres', 'mysql', 'sqlite']
             ),
         ),
         param(