From 7c7e45993a6d2c24fbf9e51189eacfbbb620e5b6 Mon Sep 17 00:00:00 2001
From: Phillip Cloud <417981+cpcloud@users.noreply.github.com>
Date: Tue, 12 Nov 2024 06:17:01 -0500
Subject: [PATCH] feat(api): add `modes` array aggregation

---
 ibis/backends/sql/compilers/duckdb.py |  1 +
 ibis/backends/tests/test_array.py     |  3 ++-
 ibis/expr/operations/arrays.py        |  5 +++++
 ibis/expr/types/arrays.py             | 27 +++++++++++++++++++++++++++
 4 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/ibis/backends/sql/compilers/duckdb.py b/ibis/backends/sql/compilers/duckdb.py
index 2a6b36e7e45b..de83a0efb527 100644
--- a/ibis/backends/sql/compilers/duckdb.py
+++ b/ibis/backends/sql/compilers/duckdb.py
@@ -62,6 +62,7 @@ class DuckDBCompiler(SQLGlotCompiler):
         ops.ArrayAll: "list_bool_and",
         ops.ArraySum: "list_sum",
         ops.ArrayMean: "list_avg",
+        ops.ArrayMode: "list_mode",
         ops.BitAnd: "bit_and",
         ops.BitOr: "bit_or",
         ops.BitXor: "bit_xor",
diff --git a/ibis/backends/tests/test_array.py b/ibis/backends/tests/test_array.py
index 02f811bc3f0a..5533ddd3b490 100644
--- a/ibis/backends/tests/test_array.py
+++ b/ibis/backends/tests/test_array.py
@@ -1816,8 +1816,9 @@ def _agg_with_nulls(agg, x):
         (ir.ArrayValue.mins, lambda x: _agg_with_nulls(min, x)),
         (ir.ArrayValue.maxs, lambda x: _agg_with_nulls(max, x)),
         (ir.ArrayValue.means, lambda x: _agg_with_nulls(statistics.mean, x)),
+        (ir.ArrayValue.modes, lambda x: _agg_with_nulls(statistics.mode, x)),
     ],
-    ids=["sums", "mins", "maxs", "means"],
+    ids=["sums", "mins", "maxs", "means", "modes"],
 )
 @notimpl_aggs
 @pytest.mark.parametrize(
diff --git a/ibis/expr/operations/arrays.py b/ibis/expr/operations/arrays.py
index 11687c752030..8202b21259da 100644
--- a/ibis/expr/operations/arrays.py
+++ b/ibis/expr/operations/arrays.py
@@ -292,6 +292,11 @@ class ArrayMax(ArrayAgg):
     """Compute the maximum value of an array."""
 
 
+@public
+class ArrayMode(ArrayAgg):
+    """Compute the mode of an array."""
+
+
 # in duckdb summing an array of ints leads to an int, but for other backends
 # it might lead to a float??
 @public
diff --git a/ibis/expr/types/arrays.py b/ibis/expr/types/arrays.py
index c33b0b84a008..b494d8be3f24 100644
--- a/ibis/expr/types/arrays.py
+++ b/ibis/expr/types/arrays.py
@@ -1208,6 +1208,33 @@ def alls(self) -> ir.BooleanValue:
         """
         return ops.ArrayAll(self).to_expr()
 
+    def modes(self) -> ir.Value:
+        """Return the mode of the values in the array.
+
+        See Also
+        --------
+        [`Column.mode`](./expression-generic.qmd#ibis.expr.types.generic.Column.mode)
+
+        Examples
+        --------
+        >>> import ibis
+        >>> ibis.options.interactive = True
+        >>> t = ibis.memtable({"arr": [[1, 2, 3, 3], [None, 6], [None], [], None]})
+        >>> t.mutate(mode=t.arr.modes())
+        ┏━━━━━━━━━━━━━━━━━━━━━━┳━━━━━━━┓
+        ┃ arr                  ┃ mode  ┃
+        ┡━━━━━━━━━━━━━━━━━━━━━━╇━━━━━━━┩
+        │ array<int64>         │ int64 │
+        ├──────────────────────┼───────┤
+        │ [1, 2, ... +2]       │     3 │
+        │ [None, 6]            │     6 │
+        │ [None]               │  NULL │
+        │ []                   │  NULL │
+        │ NULL                 │  NULL │
+        └──────────────────────┴───────┘
+        """
+        return ops.ArrayMode(self).to_expr()
+
     def mins(self) -> ir.NumericValue:
         """Return the minimum value in the array.