Hi all, when I query into a big table, it lead to memory error.

Here is the small script which lead to the memory error:
---------------------------------------------------------
engine = sqlalchemy.create_engine("mysql://user:passw...@127.0.0.1/
homo_sapiens_variation_56_37a")
meta = sqlalchemy.MetaData()
meta.bind = engine
Session = sessionmaker(bind = engine)
table_variation = sqlalchemy.Table('variation', meta, autoload=True)
class Variation(object): pass
mapper(Variation, table_variation)
session = Session()
al_records = session.query(Variation)
for record in al_records:  #there are 18 million records in the table
variation
    pass

---------------------------------------------------------
And here are the error information. I am using the SQLAlchemy of 0.56,
python 2.5, and OS X.  Is it a bug of SQLAlchemy? Could anyone please
help me out? Thanks.

Python(43867) malloc: *** mmap(size=262144) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
...
Python(43867) malloc: *** mmap(size=262144) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
Python(43867) malloc: *** mmap(size=2097152) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
Traceback (most recent call last):
  File "test_memory_leak.py", line 28, in <module>
    for record in al_records:  # load all 18 million records into the
memory
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/orm/query.py", line 1361, in __iter__
    return self._execute_and_instances(context)
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/orm/query.py", line 1364, in _execute_and_instances
    result = self.session.execute(querycontext.statement,
params=self._params, mapper=self._mapper_zero_or_none())
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/orm/session.py", line 755, in execute
    clause, params or {})
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/engine/base.py", line 824, in execute
    return Connection.executors[c](self, object, multiparams, params)
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/engine/base.py", line 874, in _execute_clauseelement
    return self.__execute_context(context)
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/engine/base.py", line 896, in __execute_context
    self._cursor_execute(context.cursor, context.statement,
context.parameters[0], context=context)
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/engine/base.py", line 948, in _cursor_execute
    self.dialect.do_execute(cursor, statement, parameters,
context=context)
  File "/Library/Python/2.5/site-packages/SQLAlchemy-0.5.6-py2.5.egg/
sqlalchemy/engine/default.py", line 123, in do_execute
    cursor.execute(statement, parameters)
  File "build/bdist.macosx-10.5-i386/egg/MySQLdb/cursors.py", line
173, in execute
  File "build/bdist.macosx-10.5-i386/egg/MySQLdb/connections.py", line
36, in defaulterrorhandler
MemoryError

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