Merge pull request #346 from chumaltd/retry-0.9

Use Enumerator#size for ADD CONSTRAINT example.

README.md

@@ -350,7 +350,7 @@ add_index "books", ["author_id"], name: "idx_author_id", using: :btree
 
 execute("ALTER TABLE books ADD CONSTRAINT fk_author FOREIGN KEY (author_id) REFERENCES authors (id)") do |c|
   # Execute SQL only if there is no foreign key
-  c.raw_connection.query(<<-SQL).each.length.zero?
+  c.raw_connection.query(<<-SQL).each.size.zero?
     SELECT 1 FROM information_schema.key_column_usage
      WHERE TABLE_SCHEMA = 'bookshelf'
        AND CONSTRAINT_NAME = 'fk_author' LIMIT 1