Add cross lateral join support for MyXql.

Author: William Wilkinson

lib/ecto/adapters/myxql/connection.ex

@@ -388,6 +388,7 @@ if Code.ensure_loaded?(MyXQL) do
     end
 
     defp join_on(:cross, true, _sources, _query), do: []
+    defp join_on(:cross_lateral, true, _sources, _query), do: []
     defp join_on(_qual, expr, sources, query), do: [" ON " | expr(expr, sources, query)]
 
     defp join_qual(:inner, _), do: " INNER JOIN "
@@ -397,7 +398,7 @@ if Code.ensure_loaded?(MyXQL) do
     defp join_qual(:right, _), do: " RIGHT OUTER JOIN "
     defp join_qual(:full, _),  do: " FULL OUTER JOIN "
     defp join_qual(:cross, _), do: " CROSS JOIN "
-    defp join_qual(qual, _), do: error!(nil, "#{qual} is not supported in the MyXQL Adapter")
+    defp join_qual(:cross_lateral, _), do: "CROSS JOIN LATERAL "
 
     defp where(%{wheres: wheres} = query, sources) do
       boolean(" WHERE ", wheres, sources, query)

lib/ecto/adapters/tds/connection.ex

@@ -526,7 +526,7 @@ if Code.ensure_loaded?(Tds) do
     defp join_qual(:cross), do: "CROSS JOIN "
     defp join_qual(:inner_lateral), do: "CROSS APPLY "
     defp join_qual(:left_lateral), do: "OUTER APPLY "
-    defp join_qual(qual), do: error!(nil, "#{qual} is not supported in the Tds Adapter")
+    defp join_qual(:cross_lateral), do: error!(nil, "cross lateral joins are not supported in the Tds Adapter")
 
     defp where(%Query{wheres: wheres} = query, sources) do
       boolean(" WHERE ", wheres, sources, query)

test/ecto/adapters/myxql_test.exs

@@ -1006,6 +1006,18 @@ defmodule Ecto.Adapters.MyXQLTest do
            ~s{WHERE ((s0.`id` > 0) AND (s0.`id` < ?))}
   end
 
+   test "cross lateral join with fragment" do
+    query = Schema
+            |> join(:cross_lateral, [p], q in fragment("SELECT * FROM schema2 AS s2 WHERE s2.id = ? AND s2.field = ?", p.x, ^10))
+            |> select([p, q], {p.id, q.z})
+            |> where([p], p.id > 0 and p.id < ^100)
+            |> plan()
+    assert all(query) ==
+           ~s{SELECT s0."id", f1."z" FROM "schema" AS s0 CROSS JOIN LATERAL } <>
+           ~s{(SELECT * FROM schema2 AS s2 WHERE s2.id = s0."x" AND s2.field = $1) AS f1 } <>
+           ~s{WHERE ((s0."id" > 0) AND (s0."id" < $2))}
+  end
+
   test "cross join" do
     query = from(p in Schema, cross_join: c in Schema2, select: {p.id, c.id}) |> plan()
     assert all(query) ==