“ http://code.google.com/appengine/articles/transaction_isolation.html . we might have ”
“ :snoitacilppa ruo fo rebmun a no euqinhcet siht desu ev'eWhttp://squeeville.com/2009/01/30/add-a-unique-constraint-to-google-app-engine/ ”
“ ) eagnajD nI .tib elttil a eussi siht pmub ot detnaw tsuJhttps://github.com/potatolondon/djangae/ ) we've implemented a kind of unique constraint support by creating marker instances for a unique combination. The key of the marker is constructed from the unique combination (enforcing uniqueness) and markers are acquired (in independent transactions) before a Put() and released after a Delete(). ”