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)

activerecord/CHANGELOG.md

@@ -1,3 +1,13 @@
+*   Introduce `connection.data_sources` and `connection.data_source_exists?`.
+    These methods determine what relations can be used to back Active Record
+    models (usually tables and views).
+
+    Also deprecate `SchemaCache#tables`, `SchemaCache#table_exists?` and
+    `SchemaCache#clear_table_cache!` in favor of their new data source
+    counterparts.
+
+    *Yves Senn*, *Matthew Draper*
+
 *   `ActiveRecord::Tasks::MySQLDatabaseTasks` fails if shellout to
     mysql commands (like `mysqldump`) is not successful.
 

activerecord/lib/active_record/connection_adapters/abstract/schema_statements.rb

@@ -23,6 +23,20 @@ module ActiveRecord
         table_name[0...table_alias_length].tr('.', '_')
       end
 
+      # Returns the relation names useable to back Active Record models.
+      # For most adapters this means all #tables and #views.
+      def data_sources
+        tables | views
+      end
+
+      # Checks to see if the data source +name+ exists on the database.
+      #
+      #   data_source_exists?(:ebooks)
+      #
+      def data_source_exists?(name)
+        data_sources.include?(name.to_s)
+      end
+
       # Returns an array of table names defined in the database.
       def tables(name = nil)
         raise NotImplementedError, "#tables is not implemented"

activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb

@@ -628,6 +628,7 @@ module ActiveRecord
       def tables(name = nil) # :nodoc:
         select_values("SHOW FULL TABLES", 'SCHEMA')
       end
+      alias data_sources tables
 
       def truncate(table_name, name = nil)
         execute "TRUNCATE TABLE #{quote_table_name(table_name)}", name
@@ -644,6 +645,7 @@ module ActiveRecord
 
         select_values(sql, 'SCHEMA').any?
       end
+      alias data_source_exists? table_exists?
 
       def views # :nodoc:
         select_values("SHOW FULL TABLES WHERE table_type = 'VIEW'", 'SCHEMA')

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

@@ -73,6 +73,16 @@ module ActiveRecord
           select_values("SELECT tablename FROM pg_tables WHERE schemaname = ANY(current_schemas(false))", 'SCHEMA')
         end
 
+        def data_sources # :nodoc
+          select_values(<<-SQL, 'SCHEMA')
+            SELECT c.relname
+            FROM pg_class c
+            LEFT JOIN pg_namespace n ON n.oid = c.relnamespace
+            WHERE c.relkind IN ('r', 'v','m') -- (r)elation/table, (v)iew, (m)aterialized view
+            AND n.nspname = ANY (current_schemas(false))
+          SQL
+        end
+
         # Returns true if table exists.
         # If the schema is not specified as part of +name+ then it will only find tables within
         # the current schema search path (regardless of permissions to access tables in other schemas)
@@ -89,6 +99,7 @@ module ActiveRecord
               AND n.nspname = #{name.schema ? "'#{name.schema}'" : 'ANY (current_schemas(false))'}
           SQL
         end
+        alias data_source_exists? table_exists?
 
         def views # :nodoc:
           select_values(<<-SQL, 'SCHEMA')

activerecord/lib/active_record/connection_adapters/schema_cache.rb

@@ -10,7 +10,7 @@ module ActiveRecord
         @columns      = {}
         @columns_hash = {}
         @primary_keys = {}
-        @tables       = {}
+        @data_sources = {}
       end
 
       def initialize_dup(other)
@@ -18,33 +18,38 @@ module ActiveRecord
         @columns      = @columns.dup
         @columns_hash = @columns_hash.dup
         @primary_keys = @primary_keys.dup
-        @tables       = @tables.dup
+        @data_sources = @data_sources.dup
       end
 
       def primary_keys(table_name)
-        @primary_keys[table_name] ||= table_exists?(table_name) ? connection.primary_key(table_name) : nil
+        @primary_keys[table_name] ||= data_source_exists?(table_name) ? connection.primary_key(table_name) : nil
       end
 
       # A cached lookup for table existence.
-      def table_exists?(name)
-        prepare_tables if @tables.empty?
-        return @tables[name] if @tables.key? name
+      def data_source_exists?(name)
+        prepare_data_sources if @data_sources.empty?
+        return @data_sources[name] if @data_sources.key? name
 
-        @tables[name] = connection.table_exists?(name)
+        @data_sources[name] = connection.data_source_exists?(name)
       end
+      alias table_exists? data_source_exists?
+      deprecate :table_exists? => "use #data_source_exists? instead"
+
 
       # Add internal cache for table with +table_name+.
       def add(table_name)
-        if table_exists?(table_name)
+        if data_source_exists?(table_name)
           primary_keys(table_name)
           columns(table_name)
           columns_hash(table_name)
         end
       end
 
-      def tables(name)
-        @tables[name]
+      def data_sources(name)
+        @data_sources[name]
       end
+      alias tables data_sources
+      deprecate :tables => "use #data_sources instead"
 
       # Get the columns for a table
       def columns(table_name)
@@ -64,36 +69,38 @@ module ActiveRecord
         @columns.clear
         @columns_hash.clear
         @primary_keys.clear
-        @tables.clear
+        @data_sources.clear
         @version = nil
       end
 
       def size
-        [@columns, @columns_hash, @primary_keys, @tables].map(&:size).inject :+
+        [@columns, @columns_hash, @primary_keys, @data_sources].map(&:size).inject :+
       end
 
-      # Clear out internal caches for table with +table_name+.
-      def clear_table_cache!(table_name)
-        @columns.delete table_name
-        @columns_hash.delete table_name
-        @primary_keys.delete table_name
-        @tables.delete table_name
+      # Clear out internal caches for the data source +name+.
+      def clear_data_source_cache!(name)
+        @columns.delete name
+        @columns_hash.delete name
+        @primary_keys.delete name
+        @data_sources.delete name
       end
+      alias clear_table_cache! clear_data_source_cache!
+      deprecate :clear_table_cache! => "use #clear_data_source_cache! instead"
 
       def marshal_dump
         # if we get current version during initialization, it happens stack over flow.
         @version = ActiveRecord::Migrator.current_version
-        [@version, @columns, @columns_hash, @primary_keys, @tables]
+        [@version, @columns, @columns_hash, @primary_keys, @data_sources]
       end
 
       def marshal_load(array)
-        @version, @columns, @columns_hash, @primary_keys, @tables = array
+        @version, @columns, @columns_hash, @primary_keys, @data_sources = array
       end
 
       private
 
-        def prepare_tables
-          connection.tables.each { |table| @tables[table] = true }
+        def prepare_data_sources
+          connection.data_sources.each { |source| @data_sources[source] = true }
         end
     end
   end

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -319,10 +319,12 @@ module ActiveRecord
           row['name']
         end
       end
+      alias data_sources tables
 
       def table_exists?(table_name)
         table_name && tables(nil, table_name).any?
       end
+      alias data_source_exists? table_exists?
 
       def views # :nodoc:
         select_values("SELECT name FROM sqlite_master WHERE type = 'view' AND name <> 'sqlite_sequence'", 'SCHEMA')

activerecord/lib/active_record/model_schema.rb

@@ -213,7 +213,7 @@ module ActiveRecord
 
       # Indicates whether the table associated with this class exists
       def table_exists?
-        connection.schema_cache.table_exists?(table_name)
+        connection.schema_cache.data_source_exists?(table_name)
       end
 
       def attributes_builder # :nodoc:
@@ -290,7 +290,7 @@ module ActiveRecord
       def reset_column_information
         connection.clear_cache!
         undefine_attribute_methods
-        connection.schema_cache.clear_table_cache!(table_name)
+        connection.schema_cache.clear_data_source_cache!(table_name)
 
         reload_schema_from_cache
       end

activerecord/lib/active_record/railties/databases.rake

@@ -255,7 +255,7 @@ db_namespace = namespace :db do
         filename = File.join(ActiveRecord::Tasks::DatabaseTasks.db_dir, "schema_cache.dump")
 
         con.schema_cache.clear!
-        con.tables.each { |table| con.schema_cache.add(table) }
+        con.data_sources.each { |table| con.schema_cache.add(table) }
         open(filename, 'wb') { |f| f.write(Marshal.dump(con.schema_cache)) }
       end
 

activerecord/lib/active_record/schema_dumper.rb

@@ -89,7 +89,7 @@ HEADER
       end
 
       def tables(stream)
-        sorted_tables = @connection.tables.sort - @connection.views
+        sorted_tables = @connection.data_sources.sort - @connection.views
 
         sorted_tables.each do |table_name|
           table(table_name, stream) unless ignored?(table_name)

activerecord/lib/active_record/type_caster/connection.rb

@@ -20,7 +20,7 @@ module ActiveRecord
       private
 
       def column_for(attribute_name)
-        if connection.schema_cache.table_exists?(table_name)
+        if connection.schema_cache.data_source_exists?(table_name)
           connection.schema_cache.columns_hash(table_name)[attribute_name.to_s]
         end
       end

activerecord/test/active_record/connection_adapters/fake_adapter.rb

@@ -7,7 +7,7 @@ module ActiveRecord
 
   module ConnectionAdapters
     class FakeAdapter < AbstractAdapter
-      attr_accessor :tables, :primary_keys
+      attr_accessor :data_sources, :primary_keys
 
       @columns = Hash.new { |h,k| h[k] = [] }
       class << self
@@ -16,7 +16,7 @@ module ActiveRecord
 
       def initialize(connection, logger)
         super
-        @tables       = []
+        @data_sources = []
         @primary_keys = {}
         @columns      = self.class.columns
       end
@@ -37,7 +37,7 @@ module ActiveRecord
         @columns[table_name]
       end
 
-      def table_exists?(*)
+      def data_source_exists?(*)
         true
       end
 

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"
 

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
 

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

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],

activerecord/test/models/contact.rb

@@ -3,7 +3,7 @@ module ContactFakeColumns
     base.class_eval do
       establish_connection(:adapter => 'fake')
 
-      connection.tables = [table_name]
+      connection.data_sources = [table_name]
       connection.primary_keys = {
         table_name => 'id'
       }