SQLAlchemy & pseudo-hash indexing in MySQL

gistfile1.txt

import binascii

def crc32(val):
    """Have to do this with binascii's crc32 which is signed (MySQL's is unsigned)"""
    return binascii.crc32(val) & 0xffffffff

def crc32_of(other_field):
    """Context sensitive default for SQLAlchemy inserts
    Usage (in model definition):

    foo = Column('foo_col', VARCHAR(50))
    foo_crc32 = Column('foo_crc32', Integer, default=crc32_of('foo_col'), onupdate=crc32_of('foo_col'))
    """
    def _crc32(context):
        return crc32(context.current_parameters[other_field])
    return _crc32