sqlalchemy ‘word‘ used in key specification without a key length

语句

df.to_sql('ciku', con=engine,if_exists='replace')

报错

 (1170, "BLOB/TEXT column 'word' used in key specification without a key length" [SQL: CREATE INDEX ix_ciku_word ON ciku (word)]
(Background on this error at: http://sqlalche.me/e/14/e3q8)

原因是主值是longtext格式，dataframe创建index即可