On Jul 25, 7:30 am, "Nick Johnson (Google)" <nick.john...@google.com> wrote:
> The first part specifically refers to ancestor queries. Ancestor queries > always operate on the latest copy of the data, as they're restricted to an > entity group; regular queries don't have that guarantee. I understand that, but my problem is with the indexes: even in the scope of HR + transactions, the doc is confusing regarding wether or not there can be a race-condition on indexes update. For instance: - transaction A modifies entity X and commits - then transaction B happens almost concurrently: - at this point, using db.get() X will return the latest X no matter what - however, using db.GqlQuery() with a predicate that matches X *may not* return X because the indexes may not be done updating yet (the A - > B thing in the doc) So is this race-condition possible or not? No matter what, you might wanna rewrite a couple sentences in this article :) > > My understanding of this article is therefore the following (assuming > > an HR datastore and that we are inside a transaction): > > > 1) Using db.get() / db.put() on an entity always executes on its > > latest version: no race conditions possible, period. > > -> Observations in my app appears to confirm that behavior. > > Correct, with the usual caveat about transactionality (if you're not doing > this inside a transaction, you have a potential race condition). Yes, I was assuming HR datastore + transaction (see above). > > 2) Using db.GqlQuery() / db.put() on entities in the same entity group > > might still be subject to race-conditions: for instance, a previously > > *committed* transaction modified the entities that would be returned > > by the query in the later transactions, but the datastore indexes are > > not up-to-date yet (or something like that), so the query doesn't see > > the updated entities - even if calling db.get() directly on them would > > return the versions that match the query. > > -> I've reviewed my code carefully and I think I'm seeing such race > > conditions in my app. > > Correct - but again, any update outside a transaction always has possible > race conditions. Same here: I was also assuming HR datastore + transaction + ancestor queries (by definition since inside a transaction). So is my code wrong or am I observing some very rare but expected race conditions? Thanks - Pol -- You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to google-appengine@googlegroups.com. To unsubscribe from this group, send email to google-appengine+unsubscr...@googlegroups.com. For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en.
