Pandas写表到MySQL:"无法回滚"

Question

我需要帮助才能使这个工作.我有一个pd.DataFrame (df),我需要加载到MySQL数据库.我不明白错误消息的含义以及如何解决它.

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这是我试过的:

    import MySQLdb
    from pandas.io import sql

    #METHOD 1 
    db=MySQLdb.connect(host="***",port=***,user="***",passwd="***",db="***")
    df.to_sql(con=db, name='forecast', if_exists='replace', flavor='mysql')
    ##Also tried
    sql.write_frame(df, con=db, name='forecast', if_exists='replace', flavor='mysql')

   **DatabaseError**: Execution failed on sql: SHOW TABLES LIKE %s
   (2006, 'MySQL server has gone away')
   unable to rollback


   #METHOD 2: using sqlalchemy
   from sqlalchemy import create_engine

   engine =   create_engine("mysql+mysqldb://**username***:**passwd**@***host***:3306/**dbname**")
   conn = engine.raw_connection()
   df.to_sql(name='demand_forecast_t', con=conn,if_exists='replace',    flavor='mysql',index=False, index_label='rowID')
   conn.close()

错误消息是:

**OperationalError**: DatabaseError: Execution failed on sql: SHOW TABLES LIKE %s
(2006, 'MySQL server has gone away') unable to rollback

Answer 1

使用sqlalchemy时,您应该传递引擎而不是原始连接:

engine = create_engine("mysql+mysqldb://...")
df.to_sql('demand_forecast_t', engine, if_exists='replace', index=False)

不使用sqlalchemy写入MySQL(如此指定flavor='mysql')不推荐使用.

当问题是你有一个太大的框架可以一次写入时,你可以使用chunksize关键字(参见docstring).例如:

df.to_sql('demand_forecast_t', engine, if_exists='replace', chunksize=10000)