introduce `conn.data_source_exists?` and `conn.data_sources`.

These new methods are used from the Active Record model layer to
determine which relations are viable to back a model. These new methods
allow us to change `conn.tables` in the future to only return tables and
no views. Same for `conn.table_exists?`.

The goal is to provide the following introspection methods on the
connection:

* `tables`
* `table_exists?`
* `views`
* `view_exists?`
* `data_sources` (views + tables)
* `data_source_exists?` (views + tables)

4 files changed, 31 insertions, 3 deletions

diff --git a/activerecord/test/cases/adapter_test.rb b/activerecord/test/cases/adapter_test.rb
index 9a111b37cd..62579a4a7a 100644
--- a/activerecord/test/cases/adapter_test.rb
+++ b/activerecord/test/cases/adapter_test.rb
@@ -36,6 +36,21 @@ module ActiveRecord
       assert !@connection.table_exists?(nil)
     end
 
+    def test_data_sources
+      data_sources = @connection.data_sources
+      assert data_sources.include?("accounts")
+      assert data_sources.include?("authors")
+      assert data_sources.include?("tasks")
+      assert data_sources.include?("topics")
+    end
+
+    def test_data_source_exists?
+      assert @connection.data_source_exists?("accounts")
+      assert @connection.data_source_exists?(:accounts)
+      assert_not @connection.data_source_exists?("nonexistingtable")
+      assert_not @connection.data_source_exists?(nil)
+    end
+
     def test_indexes
       idx_name = "accounts_idx"
 
diff --git a/activerecord/test/cases/adapters/postgresql/schema_test.rb b/activerecord/test/cases/adapters/postgresql/schema_test.rb
index bee612d8d3..f89a394f96 100644
--- a/activerecord/test/cases/adapters/postgresql/schema_test.rb
+++ b/activerecord/test/cases/adapters/postgresql/schema_test.rb
@@ -5,9 +5,11 @@ require 'support/schema_dumping_helper'
 module PGSchemaHelper
   def with_schema_search_path(schema_search_path)
     @connection.schema_search_path = schema_search_path
+    @connection.schema_cache.clear!
     yield if block_given?
   ensure
     @connection.schema_search_path = "'$user', public"
+    @connection.schema_cache.clear!
   end
 end
 
diff --git a/activerecord/test/cases/connection_adapters/schema_cache_test.rb b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
index c7531f5418..db832fe55d 100644
--- a/activerecord/test/cases/connection_adapters/schema_cache_test.rb
+++ b/activerecord/test/cases/connection_adapters/schema_cache_test.rb
@@ -29,7 +29,7 @@ module ActiveRecord
       def test_clearing
         @cache.columns('posts')
         @cache.columns_hash('posts')
-        @cache.tables('posts')
+        @cache.data_sources('posts')
         @cache.primary_keys('posts')
 
         @cache.clear!
@@ -40,17 +40,22 @@ module ActiveRecord
       def test_dump_and_load
         @cache.columns('posts')
         @cache.columns_hash('posts')
-        @cache.tables('posts')
+        @cache.data_sources('posts')
         @cache.primary_keys('posts')
 
         @cache = Marshal.load(Marshal.dump(@cache))
 
         assert_equal 11, @cache.columns('posts').size
         assert_equal 11, @cache.columns_hash('posts').size
-        assert @cache.tables('posts')
+        assert @cache.data_sources('posts')
         assert_equal 'id', @cache.primary_keys('posts')
       end
 
+      def test_table_methods_deprecation
+        assert_deprecated { assert @cache.table_exists?('posts') }
+        assert_deprecated { assert @cache.tables('posts') }
+        assert_deprecated { @cache.clear_table_cache!('posts') }
+      end
     end
   end
 end
diff --git a/activerecord/test/cases/view_test.rb b/activerecord/test/cases/view_test.rb
index d7b3e223ed..e80d8bd584 100644
--- a/activerecord/test/cases/view_test.rb
+++ b/activerecord/test/cases/view_test.rb
@@ -44,9 +44,15 @@ module ViewBehavior
 
   def test_table_exists
     view_name = Ebook.table_name
+    # TODO: switch this assertion around once we changed #tables to not return views.
     assert @connection.table_exists?(view_name), "'#{view_name}' table should exist"
   end
 
+  def test_views_ara_valid_data_sources
+    view_name = Ebook.table_name
+    assert @connection.data_source_exists?(view_name), "'#{view_name}' should be a data source"
+  end
+
   def test_column_definitions
     assert_equal([["id", :integer],
                   ["name", :string],