使用session.merge与sqlalchemy时的IntegrityError

Question

我使用session.merge（obj1）来插入和插入行。我偶尔会遇到像这样的错误：

(pymysql.err.IntegrityError) (1062, u"Duplicate entry 'q/FtMv4syu5QXenCXvx6ZGhbLSFYSbo6Kgv8sjuZDZwW4j1Zh3ZFHtey/aqVOe5j' for key 'PRIMARY'")

traceback


Traceback (most recent call last):
  File "/var/task/streaming_lambda.py", line 71, in lambda_handler
    session.commit()
  File "/var/task/sqlalchemy/orm/session.py", line 874, in commit
    self.transaction.commit()
  File "/var/task/sqlalchemy/orm/session.py", line 461, in commit
    self._prepare_impl()
  File "/var/task/sqlalchemy/orm/session.py", line 441, in _prepare_impl
    self.session.flush()
  File "/var/task/sqlalchemy/orm/session.py", line 2137, in flush
    self._flush(objects)
  File "/var/task/sqlalchemy/orm/session.py", line 2257, in _flush
    transaction.rollback(_capture_exception=True)
  File "/var/task/sqlalchemy/util/langhelpers.py", line 60, in __exit__
    compat.reraise(exc_type, exc_value, exc_tb)
  File "/var/task/sqlalchemy/orm/session.py", line 2221, in _flush
    flush_context.execute()
  File "/var/task/sqlalchemy/orm/unitofwork.py", line 389, in execute
    rec.execute(self)
  File "/var/task/sqlalchemy/orm/unitofwork.py", line 548, in execute
    uow
  File "/var/task/sqlalchemy/orm/persistence.py", line 181, in save_obj
    mapper, table, insert)
  File "/var/task/sqlalchemy/orm/persistence.py", line 799, in _emit_insert_statements
    execute(statement, multiparams)
  File "/var/task/sqlalchemy/engine/base.py", line 945, in execute
    return meth(self, multiparams, params)
  File "/var/task/sqlalchemy/sql/elements.py", line 263, in _execute_on_connection
    return connection._execute_clauseelement(self, multiparams, params)
  File "/var/task/sqlalchemy/engine/base.py", line 1053, in _execute_clauseelement
    compiled_sql, distilled_params
  File "/var/task/sqlalchemy/engine/base.py", line 1189, in _execute_context
    context)
  File "/var/task/sqlalchemy/engine/base.py", line 1393, in _handle_dbapi_exception
    exc_info
  File "/var/task/sqlalchemy/util/compat.py", line 202, in raise_from_cause
    reraise(type(exception), exception, tb=exc_tb, cause=cause)
  File "/var/task/sqlalchemy/engine/base.py", line 1182, in _execute_context
    context)
  File "/var/task/sqlalchemy/engine/default.py", line 469, in do_execute
    cursor.execute(statement, parameters)
  File "/var/task/pymysql/cursors.py", line 166, in execute
    result = self._query(query)
  File "/var/task/pymysql/cursors.py", line 322, in _query
    conn.query(q)
  File "/var/task/pymysql/connections.py", line 835, in query
    self._affected_rows = self._read_query_result(unbuffered=unbuffered)
  File "/var/task/pymysql/connections.py", line 1019, in _read_query_result
    result.read()
  File "/var/task/pymysql/connections.py", line 1302, in read
    first_packet = self.connection._read_packet()
  File "/var/task/pymysql/connections.py", line 981, in _read_packet
    packet.check_error()
  File "/var/task/pymysql/connections.py", line 393, in check_error
    err.raise_mysql_exception(self._data)
  File "/var/task/pymysql/err.py", line 107, in raise_mysql_exception
    raise errorclass(errno, errval)
IntegrityError: (pymysql.err.IntegrityError) (1062, u"Duplicate entry 'q/FtMv4syu5QXenCXvx6ZGhbLSFYSbo6Kgv8sjuZDZwW4j1Zh3ZFHtey/aqVOe5j' for key 'PRIMARY'") [SQL: u'INSERT INTO user_table (_id, collection_name, platform, created_at, updated_at, deleted, account_complete, population_current, state, stars, language, age_range, private_account, user_credit, new_user, anonymous) VALUES (%(_id)s, %(collection_name)s, %(platform)s, %(created_at)s, %(updated_at)s, %(deleted)s, %(account_complete)s, %(population_current)s, %(state)s, %(stars)s, %(language)s, %(age_range)s, %(private_account)s, %(user_credit)s, %(new_user)s, %(anonymous)s)'] [parameters: {'user_credit': 0, 'age_range': None, 'anonymous': 0, 'language': None, 'new_user': 1, 'collection_name': None, 'created_at': datetime.datetime(2000, 1, 1, 0, 0), 'deleted': 0, 'account_complete': None, 'updated_at': None, 'platform': 'undefined', 'state': None, 'stars': None, '_id': 'q/FtMv4syu5QXenCXvx6ZGhbLSFYSbo6Kgv8sjuZDZwW4j1Zh3ZFHtey/aqVOe5jmS3lKMKns0LkrC+uZEifDHg32wqWG6Efm+h4ofptf1kZSKIp54yj243Av+lQFSrQOJd5SeOcn178SodEAmfEEpRhzy3S9NW6RO1e64zpxoY=', 'private_account': 0, 'population_current': 'undefined'}]

我使用sqlalchemy 0.9.1和PyMysql 0.7.9在mysql中与RDS mysql数据库进行通信。 session.merge()如何生成重复的输入错误？这不是它的目的吗？