InvalidRequestError: VARCHAR requires a length on dialect mysql

Question

I am trying to create a remote database using mysql on an Ubuntu machine running 12.04.

It has a root user with remote login enabled and no password.I have started the server.

output of

sudo netstat -tap | grep mysql

shows

tcp        0      0 localhost:mysql         *:*                     LISTEN      13246/mysqld

I have created a database called nwtopology using (as mentioned root doesn't have a password yet.)

 create database nwtopology
 grant all privileges on *.* to [email protected]
 FLUSH PRIVILEGES;

From the client machine that also runs Ubuntu 12.04 I use a python script to connect to the remote mysql database using sqlalchemy.

from pox.core import core
import pox.openflow.libopenflow_01 as of
import re
import datetime
import time
from sqlalchemy import create_engine, ForeignKey
from sqlalchemy import Column, Date, Integer, String
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship, backref
from sqlalchemy import create_engine
from sqlalchemy.orm import sessionmaker
from sqlalchemy.sql.expression import exists

log = core.getLogger()
engine = create_engine('mysql://[email protected]/nwtopology', echo=False)
Base = declarative_base()
Session = sessionmaker(bind=engine)
session = Session()

class SourcetoPort(Base):
    """"""
    __tablename__ = 'source_to_port'
    id = Column(Integer, primary_key=True)
    port_no        = Column(Integer)
    src_address    = Column(String,index=True)

    #-----------------------------------------
    def __init__(self, src_address,port_no):
        """"""
        self.src_address = src_address
        self.port_no     = port_no


#create tables
Base.metadata.create_all(engine)

The last line

Base.metadata.create_all(engine)

returns the error

 File "/usr/lib/python2.7/dist-packages/sqlalchemy/sql/compiler.py", line 1699, in visit_string
    return self.visit_VARCHAR(type_)
  File "/usr/lib/python2.7/dist-packages/sqlalchemy/dialects/mysql/base.py", line 1654, in visit_VARCHAR
    self.dialect.name)
InvalidRequestError: VARCHAR requires a length on dialect mysql

What does this mean? how can I set VARCHAR length on mysql? I am very new to sqlalchemy and mysql.

Solution

Add the length to your String column:

src_address = Column(String(16), index=True)

Comments

[Leo]

Thank you! For some reason I didn't need to specify the length in my local environment, but it seems Google Cloud SQL required it.