google app engine - GAE datastore transaction with multiple ancestors entity groups -


it not clear me, documentation, ancestor boundary transaction. closest one, or root one?

i have root entity (a) , has few descendants (b1, b2 ... bn) , can have many ancestors (c1, c2...). make transactions on c entities (cs), ancestor query based on b entity. question is, change in cs under b1 throw concurrentmodificationexception if transaction changes cs under b2 in same time?

do cs belong same entity group under grandparent or entity groups divided in smaller "sub - entity groups" i.e. every group of cs under b has own entity group?

the boundary root.

from https://developers.google.com/appengine/docs/python/datastore/transactions:

all datastore operations in transaction must operate on entities in same entity group

and

each root entity belongs separate entity group, single transaction cannot create or operate on more 1 root entity

so under 1 entity group.


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