From 0b7817e420eb8e345c6d78d7731459514bba0599 Mon Sep 17 00:00:00 2001
From: Zach Daniel <zachary.s.daniel@gmail.com>
Date: Thu, 4 Mar 2021 22:50:12 -0500
Subject: [PATCH] fix: add back in inner join detection logic

---
 lib/data_layer.ex | 130 ++++++++++++++++++++++++++++------------------
 1 file changed, 79 insertions(+), 51 deletions(-)

diff --git a/lib/data_layer.ex b/lib/data_layer.ex
index de28bb9..ba516ff 100644
--- a/lib/data_layer.ex
+++ b/lib/data_layer.ex
@@ -661,68 +661,96 @@ defmodule AshPostgres.DataLayer do
     })
   end
 
+  @known_inner_join_operators [
+                                Eq,
+                                GreaterThan,
+                                GreaterThanOrEqual,
+                                In,
+                                IsNil,
+                                LessThanOrEqual,
+                                LessThan,
+                                NotEq
+                              ]
+                              |> Enum.map(&Module.concat(Ash.Query.Operator, &1))
+
+  @known_inner_join_functions [
+                                Ago,
+                                Contains,
+                                IsNil
+                              ]
+                              |> Enum.map(&Module.concat(Ash.Query.Function, &1))
+
+  @known_inner_join_predicates @known_inner_join_functions ++ @known_inner_join_operators
+
   # For consistency's sake, this logic was removed.
   # We can revisit it sometime though.
-  defp can_inner_join?(_, _), do: false
-  # defp can_inner_join?(path, expr, seen_an_or? \\ false)
+  defp can_inner_join?(path, expr, seen_an_or? \\ false)
 
-  # defp can_inner_join?(path, %{expression: expr}, seen_an_or?),
-  #   do: can_inner_join?(path, expr, seen_an_or?)
+  defp can_inner_join?(path, %{expression: expr}, seen_an_or?),
+    do: can_inner_join?(path, expr, seen_an_or?)
 
-  # defp can_inner_join?(_path, expr, _seen_an_or?) when expr in [nil, true, false], do: true
+  defp can_inner_join?(_path, expr, _seen_an_or?) when expr in [nil, true, false], do: true
 
-  # defp can_inner_join?(path, %BooleanExpression{op: :and, left: left, right: right}, seen_an_or?) do
-  #   can_inner_join?(path, left, seen_an_or?) || can_inner_join?(path, right, seen_an_or?)
-  # end
+  defp can_inner_join?(path, %BooleanExpression{op: :and, left: left, right: right}, seen_an_or?) do
+    can_inner_join?(path, left, seen_an_or?) || can_inner_join?(path, right, seen_an_or?)
+  end
 
-  # defp can_inner_join?(path, %BooleanExpression{op: :or, left: left, right: right}, _) do
-  #   can_inner_join?(path, left, true) && can_inner_join?(path, right, true)
-  # end
+  defp can_inner_join?(path, %BooleanExpression{op: :or, left: left, right: right}, _) do
+    can_inner_join?(path, left, true) && can_inner_join?(path, right, true)
+  end
 
-  # defp can_inner_join?(
-  #        path,
-  #        %Not{expression: %BooleanExpression{op: :or, left: left, right: right}},
-  #        seen_an_or?
-  #      ) do
-  #   can_inner_join?(
-  #     path,
-  #     %BooleanExpression{
-  #       op: :and,
-  #       left: %Not{expression: left},
-  #       right: %Not{expression: right}
-  #     },
-  #     # We count `not` as having seen an `or` to be conservative.
-  #     # The reason for this is that `id = 1 or not(id = 1)`
-  #     true
-  #   )
-  # end
+  defp can_inner_join?(
+         path,
+         %Not{expression: %BooleanExpression{op: :or, left: left, right: right}},
+         seen_an_or?
+       ) do
+    can_inner_join?(
+      path,
+      %BooleanExpression{
+        op: :and,
+        left: %Not{expression: left},
+        right: %Not{expression: right}
+      },
+      seen_an_or?
+    )
+  end
 
-  # defp can_inner_join?(path, %Not{expression: expression}, seen_an_or?) do
-  #   can_inner_join?(path, expression, seen_an_or?)
-  # end
+  defp can_inner_join?(path, %Not{expression: expression}, seen_an_or?) do
+    can_inner_join?(path, expression, seen_an_or?)
+  end
 
-  # defp can_inner_join?(
-  #        search_path,
-  #        %{__operator__?: true, left: %Ref{relationship_path: relationship_path}},
-  #        seen_an_or?
-  #      )
-  #      when search_path == relationship_path do
-  #   not seen_an_or?
-  # end
+  defp can_inner_join?(
+         search_path,
+         %struct{__operator__?: true, left: %Ref{relationship_path: relationship_path}},
+         seen_an_or?
+       )
+       when search_path == relationship_path and struct in @known_inner_join_predicates do
+    not seen_an_or?
+  end
 
-  # defp can_inner_join?(
-  #        search_path,
-  #        %{__function__?: true, arguments: arguments},
-  #        seen_an_or?
-  #      ) do
-  #   if Enum.any?(arguments, &match?(%Ref{relationship_path: ^search_path}, &1)) do
-  #     not seen_an_or?
-  #   else
-  #     true
-  #   end
-  # end
+  defp can_inner_join?(
+         search_path,
+         %struct{__operator__?: true, right: %Ref{relationship_path: relationship_path}},
+         seen_an_or?
+       )
+       when search_path == relationship_path and struct in @known_inner_join_predicates do
+    not seen_an_or?
+  end
 
-  # defp can_inner_join?(_, _, _), do: true
+  defp can_inner_join?(
+         search_path,
+         %struct{__function__?: true, arguments: arguments},
+         seen_an_or?
+       )
+       when struct in @known_inner_join_predicates do
+    if Enum.any?(arguments, &match?(%Ref{relationship_path: ^search_path}, &1)) do
+      not seen_an_or?
+    else
+      true
+    end
+  end
+
+  defp can_inner_join?(_, _, _), do: false
 
   @impl true
   def add_aggregate(query, aggregate, _resource) do