Synonym on deferred propery loads too soon, depending on property name

I was trying to combine deferred loading of a property with using a synonym and came up with the following property definitions:

'_zwop' : deferred(habba_table.c.zwop),
'zwop' : synonym('_zwop', map_column=True),

This works, the zwop property loading is deferred and a SELECT is issued on first access. When the property is renamed to xwop, loading is not deferred.

The python code is in the attached zwop.py. When you change the name to awop, bwop, cwop ... zwop, deferring works 14 times, and fails to work 12 times. The captured output is attached as a-zwop.log. There is a pattern in the results:

awop ok
bwop ok
cwop ok
dwop fails
ewop ok
fwop fails
gwop fails
hwop fails
iwop ok
jwop ok
kwop ok
lwop fails
mwop ok
nwop fails
owop fails
pwop fails
qwop ok
rwop ok
swop ok
twop fails
uwop ok
vwop fails
wwop fails
xwop fails
ywop ok
zwop ok

The pattern varies when you replace wop with something_else, but it always repeats itself after 8 letters.

The attached script a-z runs zwop.py 26 times for the letter a-z, changing the string zwop to a-z plus a suffix supplied on the command line. For the result above run:

a-z wop

To get a quick overview of the pattern I used this:

./a-z suffix | grep SELECT | sed "s/.*SELECT/SELECT/" | sort -u

I run Debian stable, python 2.5.2-3 and python-sqlalchemy 0.5.6-1~bpo50+1 (from backports.org).

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