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# Copyright 2011-2012 GRNET S.A. All rights reserved.
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#
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# Redistribution and use in source and binary forms, with or
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# without modification, are permitted provided that the following
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# conditions are met:
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#
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#   1. Redistributions of source code must retain the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer.
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#
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#   2. Redistributions in binary form must reproduce the above
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#      copyright notice, this list of conditions and the following
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#      disclaimer in the documentation and/or other materials
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#      provided with the distribution.
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#
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# THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
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# OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
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# WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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# PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
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# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
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# AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
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# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
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# ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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# POSSIBILITY OF SUCH DAMAGE.
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#
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# The views and conclusions contained in the software and
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# documentation are those of the authors and should not be
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# interpreted as representing official policies, either expressed
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# or implied, of GRNET S.A.
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from sqlalchemy import create_engine
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#from sqlalchemy.event import listen
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from sqlalchemy.pool import NullPool
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from sqlalchemy.interfaces import PoolListener
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class DBWrapper(object):
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    """Database connection wrapper."""
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    def __init__(self, db):
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        if db.startswith('sqlite://'):
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            class ForeignKeysListener(PoolListener):
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                def connect(self, dbapi_con, con_record):
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                    dbapi_con.execute('pragma foreign_keys=ON;')
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                    dbapi_con.execute('pragma case_sensitive_like=ON;')
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            self.engine = create_engine(
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                db, connect_args={'check_same_thread': False},
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                poolclass=NullPool, listeners=[ForeignKeysListener()],
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                isolation_level='SERIALIZABLE')
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        #elif db.startswith('mysql://'):
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        #    db = '%s?charset=utf8&use_unicode=0' %db
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        #    self.engine = create_engine(db, convert_unicode=True)
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        else:
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            #self.engine = create_engine(db, pool_size=0, max_overflow=-1)
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            self.engine = create_engine(
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                db, poolclass=NullPool, isolation_level='READ COMMITTED')
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        self.engine.echo = False
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        self.engine.echo_pool = False
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        self.conn = self.engine.connect()
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        self.trans = None
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    def close(self):
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        self.conn.close()
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        self.conn = None
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    def execute(self):
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        self.trans = self.conn.begin()
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    def commit(self):
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        self.trans.commit()
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        self.trans = None
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    def rollback(self):
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        self.trans.rollback()
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        self.trans = None