我正在把数据从postgres移到snowflake。最初它是有效的，但我补充说：

df_postgres["dateutc"]= pd.to_datetime(df_postgres["dateutc"])

因为日期格式不正确地加载到snowflake，现在我看到这个错误：
sql编译错误：错误行1的位置87无效标识符“dateutc”
这是我的密码：

from sqlalchemy import create_engine
import pandas as pd
import glob
import os
from config import postgres_user, postgres_pass, host,port, postgres_db, snow_user, snow_pass,snow_account,snow_warehouse   
from snowflake.connector.pandas_tools import pd_writer
from snowflake.sqlalchemy import URL

from sqlalchemy.dialects import registry
registry.register('snowflake', 'snowflake.sqlalchemy', 'dialect')

engine = create_engine(f'postgresql://{postgres_user}:{postgres_pass}@{host}:{port}/{postgres_db}')

conn = engine.connect()

# reads query

df_postgres = pd.read_sql("SELECT * FROM rok.my_table", conn)

# dropping these columns

drop_cols=['RPM', 'RPT']
df_postgres.drop(drop_cols, inplace=True, axis=1)

# changed columns to lowercase

df_postgres.columns = df_postgres.columns.str.lower()

df_postgres["dateutc"]= pd.to_datetime(df_postgres["dateutc"])

print(df_postgres.dateutc.dtype)

sf_conn = create_engine(URL(
    account = snow_account,
    user = snow_user,
    password = snow_pass,
    database = 'test',
    schema = 'my_schema',
    warehouse = 'test',
    role = 'test',
))

df_postgres.to_sql(name='my_table',
                 index = False,  
                 con = sf_conn,
                 if_exists = 'append', 
                 chunksize = 300,
                 method = pd_writer)