Avoid coercing all SELECTs with the same column name to the same value

activerecord/lib/active_record/connection_adapters/postgresql/database_statements.rb

@@ -96,12 +96,12 @@ def execute(sql, name = nil)
 
         def exec_query(sql, name = "SQL", binds = [], prepare: false)
           execute_and_clear(sql, name, binds, prepare: prepare) do |result|
-            types = {}
+            types = []
             fields = result.fields
             fields.each_with_index do |fname, i|
               ftype = result.ftype i
               fmod  = result.fmod i
-              types[fname] = get_oid_type(ftype, fmod, fname)
+              types << get_oid_type(ftype, fmod, fname)
             end
             build_result(columns: fields, rows: result.values, column_types: types)
           end

activerecord/lib/active_record/result.rb

@@ -34,13 +34,13 @@ module ActiveRecord
   class Result
     include Enumerable
 
-    attr_reader :columns, :rows, :column_types
+    attr_reader :columns, :rows, :types
 
-    def initialize(columns, rows, column_types = {})
+    def initialize(columns, rows, types = [])
       @columns      = columns
       @rows         = rows
       @hash_rows    = nil
-      @column_types = column_types
+      @types        = types
     end
 
     # Returns true if this result set includes the column named +name+
@@ -110,13 +110,15 @@ def cast_values(type_overrides = {}) # :nodoc:
       if columns.one?
         # Separated to avoid allocating an array per row
 
-        type = column_type(columns.first, type_overrides)
+        type = column_type(columns.first, 0, type_overrides)
 
         rows.map do |(value)|
           type.deserialize(value)
         end
       else
-        types = columns.map { |name| column_type(name, type_overrides) }
+        types = columns.map.with_index do |name, i|
+          column_type(name, i, type_overrides)
+        end
 
         rows.map do |values|
           Array.new(values.size) { |i| types[i].deserialize(values[i]) }
@@ -127,14 +129,22 @@ def cast_values(type_overrides = {}) # :nodoc:
     def initialize_copy(other)
       @columns      = columns.dup
       @rows         = rows.dup
-      @column_types = column_types.dup
       @hash_rows    = nil
+      @types        = types.dup
+    end
+
+    def column_types
+      if @types.present?
+        Hash[@columns.zip(@types)]
+      else
+        {}
+      end
     end
 
     private
-      def column_type(name, type_overrides = {})
+      def column_type(name, index, type_overrides = {})
         type_overrides.fetch(name) do
-          column_types.fetch(name, Type.default_value)
+          types[index] || Type.default_value
         end
       end
 

activerecord/test/cases/adapters/postgresql/postgresql_adapter_test.rb

@@ -3,6 +3,8 @@
 require "cases/helper"
 require "support/ddl_helper"
 require "support/connection_helper"
+require "models/book"
+require "models/author"
 
 module ActiveRecord
   module ConnectionAdapters
@@ -342,6 +344,25 @@ def test_reload_type_map_for_newly_defined_types
         reset_connection
       end
 
+      def test_support_different_types_for_results_with_the_same_column_name
+        result = @connection.select_all "select COALESCE(NULL, 'four'), COALESCE(NULL, 4)"
+        assert_equal [["four", 4]], result.cast_values
+        assert_instance_of(ActiveRecord::Type::Text, result.types[0])
+        assert_instance_of(ActiveRecord::Type::Integer, result.types[1])
+      end
+
+      def test_support_different_types_for_columns_with_the_same_name_but_different_tables
+        author = Author.create!(name: "Jules Verne", status: "deceased")
+        Book.create!(author: author, name: "Around the World in Eighty Days", status: :published)
+        result = @connection.select_all <<~SQL
+          SELECT authors.status, books.status
+          FROM authors
+          INNER JOIN books ON books.author_id = authors.id
+          WHERE books.name = 'Around the World in Eighty Days'
+        SQL
+        assert_equal [["deceased", 2]], result.cast_values
+      end
+
       def test_only_reload_type_map_once_for_every_unrecognized_type
         reset_connection
         connection = ActiveRecord::Base.connection

activerecord/test/cases/json_serialization_test.rb

@@ -268,7 +268,7 @@ def test_should_allow_except_option_for_list_of_authors
       authors = [@david, @mary]
       encoded = ActiveSupport::JSON.encode(authors, except: [
         :name, :author_address_id, :author_address_extra_id,
-        :organization_id, :owned_essay_id
+        :organization_id, :owned_essay_id, :status
       ])
       assert_equal %([{"id":1},{"id":2}]), encoded
     end

activerecord/test/cases/result_test.rb

@@ -69,7 +69,7 @@ def result
     test "cast_values returns rows after type casting" do
       values = [["1.1", "2.2"], ["3.3", "4.4"]]
       columns = ["col1", "col2"]
-      types = { "col1" => Type::Integer.new, "col2" => Type::Float.new }
+      types = [Type::Integer.new, Type::Float.new]
       result = Result.new(columns, values, types)
 
       assert_equal [[1, 2.2], [3, 4.4]], result.cast_values
@@ -78,7 +78,7 @@ def result
     test "cast_values uses identity type for unknown types" do
       values = [["1.1", "2.2"], ["3.3", "4.4"]]
       columns = ["col1", "col2"]
-      types = { "col1" => Type::Integer.new }
+      types = [Type::Integer.new]
       result = Result.new(columns, values, types)
 
       assert_equal [[1, "2.2"], [3, "4.4"]], result.cast_values
@@ -87,7 +87,7 @@ def result
     test "cast_values returns single dimensional array if single column" do
       values = [["1.1"], ["3.3"]]
       columns = ["col1"]
-      types = { "col1" => Type::Integer.new }
+      types = [Type::Integer.new]
       result = Result.new(columns, values, types)
 
       assert_equal [1, 3], result.cast_values
@@ -96,7 +96,7 @@ def result
     test "cast_values can receive types to use instead" do
       values = [["1.1", "2.2"], ["3.3", "4.4"]]
       columns = ["col1", "col2"]
-      types = { "col1" => Type::Integer.new, "col2" => Type::Float.new }
+      types = [Type::Integer.new, Type::Float.new]
       result = Result.new(columns, values, types)
 
       assert_equal [[1.1, 2.2], [3.3, 4.4]], result.cast_values("col1" => Type::Float.new)

activerecord/test/schema/schema.rb

@@ -72,6 +72,7 @@
     t.references :author_address_extra
     t.string :organization_id
     t.string :owned_essay_id
+    t.string :status
   end
 
   create_table :author_addresses, force: true do |t|