fix Array(Array(Nothing)) (#263)

* add failing test

* add another failing test

* tests pass

* changelog

Author: ruslandoga

CHANGELOG.md

@@ -1,5 +1,9 @@
 # Changelog
 
+## Unreleased
+
+- Fix invalid `Array(Array(Nothing))` param type for params like `[[],[],[1]]` https://github.com/plausible/ecto_ch/pull/263
+
 ## 0.8.4 (2026-01-13)
 
 - Allow `Ch` [v0.7.x](https://github.com/plausible/ch/blob/master/CHANGELOG.md#070-2026-01-13) which handles disconnects better

lib/ecto/adapters/clickhouse/connection.ex

@@ -1229,10 +1229,18 @@ defmodule Ecto.Adapters.ClickHouse.Connection do
     ["Decimal64(", Integer.to_string(scale), ?)]
   end
 
+  # context: https://github.com/plausible/analytics/pull/6049#issuecomment-3850062609
   defp param_type([]), do: "Array(Nothing)"
 
-  # TODO check whole list
-  defp param_type([v | _]), do: ["Array(", param_type(v), ?)]
+  defp param_type([v | vs]) do
+    param_type = param_type(v)
+
+    if param_type == "Array(Nothing)" do
+      param_type(vs)
+    else
+      ["Array(", param_type, ?)]
+    end
+  end
 
   defp param_type(%s{}) do
     raise ArgumentError, "struct #{inspect(s)} is not supported in params"

test/ecto/adapters/clickhouse/connection_test.exs

@@ -3233,6 +3233,39 @@ defmodule Ecto.Adapters.ClickHouse.ConnectionTest do
     assert all(query) == ~s{SELECT [1,2,3] FROM "schema" AS s0}
   end
 
+  # https://github.com/plausible/ecto_ch/issues/262
+  test "empty array params" do
+    assert all(
+             from p in Post,
+               where: fragment("array(1,2,3)") in ^[[]],
+               select: p.id
+           ) ==
+             """
+             SELECT p0."id" FROM "posts" AS p0 \
+             WHERE (array(1,2,3) IN ({$0:Array(Nothing)}))\
+             """
+
+    assert all(
+             from p in Post,
+               where: fragment("array(1,2,3)") in ^[[], [], [1, 2, 3]],
+               select: p.id
+           ) ==
+             """
+             SELECT p0."id" FROM "posts" AS p0 \
+             WHERE (array(1,2,3) IN ({$0:Array(Nothing)},{$1:Array(Nothing)},{$2:Array(Int64)}))\
+             """
+
+    assert all(
+             from p in Post,
+               where: fragment("? in ?", [1, 2, 3], ^[[], [], [1, 2, 3]]),
+               select: p.id
+           ) ==
+             """
+             SELECT p0."id" FROM "posts" AS p0 \
+             WHERE ([1,2,3] in {$0:Array(Array(Int64))})\
+             """
+  end
+
   test "maps" do
     assert all(select(Schema, [], fragment("?[site_id]", ^%{}))) ==
              ~s|SELECT {$0:Map(Nothing,Nothing)}[site_id] FROM "schema" AS s0|

test/ecto/integration/type_test.exs

@@ -377,6 +377,23 @@ defmodule Ecto.Integration.TypeTest do
     assert tag.ints == [1, 0, 3]
   end
 
+  test "array of arrays" do
+    assert TestRepo.all(
+             from n in fragment("numbers(1)"),
+               select: fragment("array(?)", n.number) in ^[[]]
+           ) == [0]
+
+    assert TestRepo.all(
+             from n in fragment("numbers(1)"),
+               select: fragment("array(?)", n.number) in ^[[], [0]]
+           ) == [1]
+
+    assert TestRepo.all(
+             from n in fragment("numbers(1)"),
+               select: fragment("array(?) in ?", n.number, ^[[], [0]])
+           ) == [1]
+  end
+
   test "empty untyped map" do
     timezones = %{}