Support INCLUDE indexes in extaneous_indexes (#133)

lib/active_record_doctor/detectors/extraneous_indexes.rb

@@ -81,11 +81,12 @@ def replaceable_with?(index1, index2)
 
         case [index1.unique, index2.unique]
         when [true, true]
-          (index2_columns - index1_columns).empty?
+          contains_all?(index1_columns, index2_columns)
         when [true, false]
           false
         else
-          prefix?(index1_columns, index2_columns)
+          prefix?(index1_columns, index2_columns) &&
+            contains_all?(index2_columns + includes(index2), includes(index1))
         end
       end
 
@@ -96,6 +97,14 @@ def opclasses(index)
       def prefix?(lhs, rhs)
         lhs.count <= rhs.count && rhs[0...lhs.count] == lhs
       end
+
+      def contains_all?(array1, array2)
+        (array2 - array1).empty?
+      end
+
+      def includes(index)
+        index.respond_to?(:include) ? Array(index.include) : []
+      end
     end
   end
 end

test/active_record_doctor/detectors/extraneous_indexes_test.rb

@@ -192,6 +192,54 @@ def test_single_column_covered_by_multi_column_on_materialized_view_is_duplicate
     end
   end
 
+  def test_include_index_covered_by_other_non_include_index
+    skip("ActiveRecord < 7.1 doesn't support include indexes") if ActiveRecord::VERSION::STRING < "7.1"
+    skip("Only PostgreSQL supports include indexes") unless postgresql?
+
+    Context.create_table(:users) do |t|
+      t.string :first_name
+      t.string :last_name
+      t.index [:last_name, :first_name]
+      t.index :last_name, include: :first_name
+    end
+
+    assert_problems(<<OUTPUT)
+remove the index index_users_on_last_name from the table users - queries should be able to use the following index instead: index_users_on_last_name_and_first_name
+OUTPUT
+  end
+
+  def test_include_index_covered_by_other_include_index
+    skip("ActiveRecord < 7.1 doesn't support include indexes") if ActiveRecord::VERSION::STRING < "7.1"
+    skip("Only PostgreSQL supports include indexes") unless postgresql?
+
+    Context.create_table(:users) do |t|
+      t.string :first_name
+      t.string :last_name
+      t.integer :age
+      t.index :last_name, include: [:age, :first_name], name: "index1_users_on_last_name"
+      t.index :last_name, include: :first_name, name: "index2_users_on_last_name"
+    end
+
+    assert_problems(<<OUTPUT)
+remove the index index2_users_on_last_name from the table users - queries should be able to use the following index instead: index1_users_on_last_name
+OUTPUT
+  end
+
+  def test_include_index_not_covered_by_other_index
+    skip("ActiveRecord < 7.1 doesn't support include indexes") if ActiveRecord::VERSION::STRING < "7.1"
+    skip("Only PostgreSQL supports include indexes") unless postgresql?
+
+    Context.create_table(:users) do |t|
+      t.string :first_name
+      t.string :last_name
+      t.integer :age
+      t.index [:first_name, :last_name]
+      t.index :last_name, include: :first_name
+    end
+
+    refute_problems
+  end
+
   def test_config_ignore_tables
     # The detector recognizes two kinds of errors and both must take
     # ignore_tables into account. We trigger those errors by indexing the