schemas set by set_table_name are respected by the mysql adapter. [#5322 state:resolved]

activerecord/lib/active_record/connection_adapters/mysql_adapter.rb

@@ -504,14 +504,28 @@ module ActiveRecord
         show_variable 'collation_database'
       end
 
-      def tables(name = nil) #:nodoc:
+      def tables(name = nil, database = nil) #:nodoc:
         tables = []
-        result = execute("SHOW TABLES", name)
+        result = execute(["SHOW TABLES", database].compact.join(' IN '), name)
         result.each { |field| tables << field[0] }
         result.free
         tables
       end
 
+      def table_exists?(name)
+        return true if super
+
+        name          = name.to_s
+        schema, table = name.split('.', 2)
+
+        unless table # A table was provided without a schema
+          table  = schema
+          schema = nil
+        end
+
+        tables(nil, schema).include? table
+      end
+
       def drop_table(table_name, options = {})
         super(table_name, options)
       end

activerecord/test/cases/adapters/mysql/schema_test.rb

@@ -0,0 +1,36 @@
+require "cases/helper"
+require 'models/post'
+require 'models/comment'
+
+module ActiveRecord
+  module ConnectionAdapters
+    class MysqlSchemaTest < ActiveRecord::TestCase
+      fixtures :posts
+
+      def setup
+        @connection = ActiveRecord::Base.connection
+        db          = Post.connection_pool.spec.config[:database]
+        table       = Post.table_name
+        @db_name    = db
+
+        @omgpost = Class.new(Post) do
+          set_table_name "#{db}.#{table}"
+          def self.name; 'Post'; end
+        end
+      end
+
+      def test_schema
+        assert @omgpost.find(:first)
+      end
+
+      def test_table_exists?
+        name = @omgpost.table_name
+        assert @connection.table_exists?(name), "#{name} table should exist"
+      end
+
+      def test_table_exists_wrong_schema
+        assert(!@connection.table_exists?("#{@db_name}.zomg"), "table should not exist")
+      end
+    end if current_adapter?(:MysqlAdapter)
+  end
+end