App Engine, How to check if all values in a list are in a string list in the datastore
You can serialize your list in a sorted fashion as a single StringProperty.  Depending on the content of your StringListProperty this may be as trivial as comma separated values.
Optionally you can use something like an md5 checksums to reduce the length of the string being stored and filtered against.
If you have a string list in the datastore that has the values:
a,b,c
How can you compare it against a list so that it only returns true if every value in the string list is present in the list?
['a', 'b'] would return false
['a', 'b', 'c'] would return true
['a', 'b', 'c', 'd', 'e'] would return true
Is this possible with GQL alone or would I need to pull put out the string list and loop over it?