mode postgresql adapters table_exists? method take the schema in to account. [#4341 state:resolved]

Signed-off-by: wycats <wycats@gmail.com>

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -670,8 +670,30 @@ module ActiveRecord
       def tables(name = nil)
         query(<<-SQL, name).map { |row| row[0] }
           SELECT tablename
+          FROM pg_tables
+          WHERE schemaname = ANY (current_schemas(false))
+        SQL
+      end
+
+      def table_exists?(name)
+        name          = name.to_s
+        schema, table = name.split('.', 2)
+
+        unless table # A table was provided without a schema
+          table  = schema
+          schema = nil
+        end
+
+        if name =~ /^"/ # Handle quoted table names
+          table  = name
+          schema = nil
+        end
+
+        query(<<-SQL).first[0].to_i > 0
+            SELECT COUNT(*)
             FROM pg_tables
-           WHERE schemaname = ANY (current_schemas(false))
+            WHERE tablename = '#{table.gsub(/(^"|"$)/,'')}'
+            #{schema ? "AND schemaname = '#{schema}'" : ''}
         SQL
       end
 

activerecord/test/cases/schema_test_postgresql.rb

@@ -52,6 +52,21 @@ class SchemaTest < ActiveRecord::TestCase
     @connection.execute "DROP SCHEMA #{SCHEMA_NAME} CASCADE"
   end
 
+  def test_table_exists?
+    [Thing1, Thing2, Thing3, Thing4].each do |klass|
+      name = klass.table_name
+      assert @connection.table_exists?(name), "'#{name}' table should exist"
+    end
+  end
+
+  def test_table_exists_wrong_schema
+    assert(!@connection.table_exists?("foo.things"), "table should not exist")
+  end
+
+  def test_table_exists_quoted_table
+    assert(@connection.table_exists?('"things.table"'), "table should exist")
+  end
+
   def test_with_schema_prefixed_table_name
     assert_nothing_raised do
       assert_equal COLUMNS, columns("#{SCHEMA_NAME}.#{TABLE_NAME}")