Sqlalchemy class _MatchType(sqltypes.Float, sqltypes.MatchType): AttributeError - mysql

Question

sometimes execute query and got this error:
ct = db.session.query(CIType).filter(
CIType.type_name == key).first() or \
db.session.query(CIType).filter(CIType.type_id == key).first()
full error info
2016-08-11 14:27:26,177 ERROR /usr/lib/python2.6/site-packages/flask/app.py 1306 - Exception on /api/v0.1/projects/search-indexer-rafael/product [GET]
Traceback (most recent call last):
File "/usr/lib/python2.6/site-packages/flask/app.py", line 1687, in wsgi_app
response = self.full_dispatch_request()
File "/usr/lib/python2.6/site-packages/flask/app.py", line 1360, in full_dispatch_request
rv = self.handle_user_exception(e)
File "/usr/lib/python2.6/site-packages/flask/app.py", line 1358, in full_dispatch_request
rv = self.dispatch_request()
File "/usr/lib/python2.6/site-packages/flask/app.py", line 1344, in dispatch_request
return self.view_functions[rule.endpoint](**req.view_args)
File "/data/webapps/cmdb-api/core/special.py", line 175, in get_project_product
product = ProjectManager().get_for_product(project_name)
File "/data/webapps/cmdb-api/lib/special/project.py", line 18, in __init__
self.ci_type = CITypeCache.get("project")
File "/data/webapps/cmdb-api/models/cmdb.py", line 458, in get
ct = db.session.query(CIType).filter(
File "/usr/lib64/python2.6/site-packages/sqlalchemy/orm/scoping.py", line 149, in do
def do(self, *args, **kwargs):
File "/usr/lib64/python2.6/site-packages/sqlalchemy/util/_collections.py", line 903, in __call__
item = dict.get(self, key)
File "/usr/lib/python2.6/site-packages/flask_sqlalchemy.py", line 201, in __init__
bind=db.engine,
File "/usr/lib/python2.6/site-packages/flask_sqlalchemy.py", line 754, in engine
return self.get_engine(self.get_app())
File "/usr/lib/python2.6/site-packages/flask_sqlalchemy.py", line 771, in get_engine
return connector.get_engine()
File "/usr/lib/python2.6/site-packages/flask_sqlalchemy.py", line 451, in get_engine
self._engine = rv = sqlalchemy.create_engine(info, **options)
File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/__init__.py", line 344, in create_engine
of 0 indicates no limit; to disable pooling, set ``poolclass`` to
File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/strategies.py", line 50, in create
File "/usr/lib64/python2.6/site-packages/sqlalchemy/engine/url.py", line 116, in get_dialect
return self.get_dialect().driver
File "/usr/lib64/python2.6/site-packages/sqlalchemy/util/langhelpers.py", line 170, in load
fn.__func__.__doc__ = doc
File "/usr/lib64/python2.6/site-packages/sqlalchemy/dialects/__init__.py", line 33, in _auto_fn
try:
File "/usr/lib64/python2.6/site-packages/sqlalchemy/dialects/mysql/__init__.py", line 8, in <module>
from . import base, mysqldb, oursql, \
File "/usr/lib64/python2.6/site-packages/sqlalchemy/dialects/mysql/base.py", line 681, in <module>
class _MatchType(sqltypes.Float, sqltypes.MatchType):
AttributeError: 'module' object has no attribute 'MatchType'
code
#special.route("/api/v0.1/projects/<string:project_name>/product",
methods=["GET"])
def get_project_product(project_name):
product = ProjectManager().get_for_product(project_name)
return jsonify(product=product)
...
goto
class ProjectManager(object):
def __init__(self):
self.ci_type = CITypeCache.get("project")
...
then
class CITypeCache(object):
#classmethod
def get(cls, key):
if key is None:
return
ct = cache.get("CIType::ID::%s" % key) or \
cache.get("CIType::Name::%s" % key)
if ct is None:
ct = db.session.query(CIType).filter(
CIType.type_name == key).first() or \
db.session.query(CIType).filter(CIType.type_id == key).first()
if ct is not None:
CITypeCache.set(ct)
return ct
The sqlalchemy's version is SQLAlchemy-1.0.8-py2.6.egg-info
and after many same error, I can't catch this error any more. What's the reason of this error?

Answer 1

I assume CIType.type_name and CIType.type_id have different data types (perhaps string and numeric types). It may lead to situation when:
db.session.query(CIType).filter(CIType.type_name == key).first()
is valid expression but:
db.session.query(CIType).filter(CIType.type_id == key).first()
produces error because of type mismatch. You need to convert key to the type_id column type in this expression.
The second expression is calculated when first expression returns no results. As written in Python documentation:
The expression x or y first evaluates x; if x is true, its value is returned; otherwise, y is evaluated and the resulting value is returned.
For example:
>>> a = 1 or 2 + '2'
>>> print a
1
>>> a = 0 or 2 + '2'
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unsupported operand type(s) for +: 'int' and 'str'