41 lines
1.7 KiB
Python
41 lines
1.7 KiB
Python
"""
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Utility functions related to databases.
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"""
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from functools import wraps
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from django.db import connection, transaction
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def commit_on_success_with_read_committed(func): # pylint: disable=invalid-name
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"""
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Decorator which executes the decorated function inside a transaction with isolation level set to READ COMMITTED.
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If the function returns a response the transaction is committed and if the function raises an exception the
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transaction is rolled back.
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Raises TransactionManagementError if there are already more than 1 level of transactions open.
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Note: This only works on MySQL.
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"""
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@wraps(func)
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def wrapper(*args, **kwargs): # pylint: disable=missing-docstring
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if connection.vendor == 'mysql':
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# The isolation level cannot be changed while a transaction is in progress. So we close any existing one.
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if connection.transaction_state:
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if len(connection.transaction_state) == 1:
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connection.commit()
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# We can commit all open transactions. But it does not seem like a good idea.
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elif len(connection.transaction_state) > 1:
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raise transaction.TransactionManagementError('Cannot change isolation level. '
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'More than 1 level of nested transactions.')
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# This will set the transaction isolation level to READ COMMITTED for the next transaction.
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cursor = connection.cursor()
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cursor.execute("SET TRANSACTION ISOLATION LEVEL READ COMMITTED")
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with transaction.commit_on_success():
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return func(*args, **kwargs)
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return wrapper
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