Slide 80: - If you write N entities that are all part of 1 entity group, it counts as 1 write.
Do this mean that cost of batch write in transaction will pay as 1 datastore operation? Do batch/query read many items from 1 entity group pay as 1 datastore operation? 2011/7/8 Ikai Lan (Google) <ika...@google.com> > Before I try to answer this question, can you take a look at these slides? > Hopefully these should clarify why things work the way they work: > > http://www.slideshare.net/ikailan/introducing-the-app-engine-datastore > > Ideally, these will raise new questions about how entity groups, index > scans, etc work. > > Ikai Lan > Developer Programs Engineer, Google App Engine > Blog: http://googleappengine.blogspot.com > Twitter: http://twitter.com/app_engine > Reddit: http://www.reddit.com/r/appengine > > > > On Thu, Jul 7, 2011 at 7:37 PM, Pol <i...@pol-online.net> wrote: > >> I'm a little confused by your answer and the concept of "zigzag >> joins". In practice, assuming the result set will end up being the >> same, is any of these 2 queries faster / better and why exactly? >> >> query = db.GqlQuery("SELECT * FROM Photo WHERE ANCESTOR IS :1 AND >> prime = TRUE ORDER BY timestamp DESC", self.user.key()) >> >> query = db.GqlQuery("SELECT * FROM Photo WHERE ANCESTOR IS :1 AND >> initialized = TRUE AND prime = TRUE ORDER BY timestamp DESC", >> self.user.key()) >> >> Regarding the 2nd set of queries I asked about, all things being >> equal, is it better to do the query with or without the ANCESTOR? >> Intuitively, I would expect the ANCESTOR version to perform faster as >> it would only run on 1 machine / entity group, but is this true? >> >> In the data model, Photo is a child of User and there 1000's more >> photos than users. Otherwise, I haven't measured performance in the >> app yet, I'd rather rely on some "official" best practices for now :) >> >> On Jul 7, 6:25 pm, "Ikai Lan (Google)" <ika...@google.com> wrote: >> > Ancestor queries don't add significant overhead, so I'm not going to >> > consider that factor. >> > >> > As far as other queries go, in general fewer indexed mean better >> performance >> > if you are doing zigzag join. However - if an index contains a small >> number >> > of results, obviously the query will return faster because there are >> simply >> > less results. Otherwise, you end up zig zagging across more indexes, >> which >> > probably will result in slower queries. It really depends on the shape >> of >> > your data. What have your obvservations been? >> > >> > Ikai Lan >> > Developer Programs Engineer, Google App Engine >> > Blog:http://googleappengine.blogspot.com >> > Twitter:http://twitter.com/app_engine >> > Reddit:http://www.reddit.com/r/appengine >> > >> > >> > >> > >> > >> > >> > >> > On Thu, Jul 7, 2011 at 6:21 PM, Pol <i...@pol-online.net> wrote: >> > > Hi, >> > >> > > Assuming the app runs on an HR database and that the number of indexes >> > > is not a problem: >> > >> > > Say that because of the data model, these queries are equivalent (i.e. >> > > return the exact same results), which one should be used to get the >> > > best performance? >> > >> > > query = db.GqlQuery("SELECT * FROM Photo WHERE ANCESTOR IS :1 AND >> > > prime = TRUE ORDER BY timestamp DESC", self.user.key()) >> > >> > > query = db.GqlQuery("SELECT * FROM Photo WHERE ANCESTOR IS :1 AND >> > > initialized = TRUE AND prime = TRUE ORDER BY timestamp DESC", >> > > self.user.key()) >> > >> > > Does the response change if somewhere else in the code, there is also >> > > this query (because of shared indexes or something)? >> > >> > > query = db.GqlQuery("SELECT * FROM Photo WHERE ANCESTOR IS :1 AND >> > > initialized = TRUE ORDER BY timestamp DESC", self.user.key()) >> > >> > > Same question, this time with these 2 other queries: >> > >> > > query = db.GqlQuery("SELECT * FROM Photo WHERE event = :1 AND prime = >> > > TRUE AND hidden = FALSE ORDER BY timestamp DESC", event.key()) >> > >> > > query = db.GqlQuery("SELECT * FROM Photo WHERE ANCESTOR IS :1 AND >> > > event = :2 AND prime = TRUE AND hidden = FALSE ORDER BY timestamp >> > > DESC", event.key().parent(), event.key()) >> > >> > > I understand the 2nd version is an ancestor query which should return >> > > consistent results (right?) but in this case, it's ok if the results >> > > are a bit stalled. >> > >> > > Thanks! >> > >> > > -- >> > > 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. >> >> -- >> 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. >> >> > -- > 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. > -- С уважением, Кулин Тимофей. Телефон: +7 (4852) 974793 ICQ: 114902104 email: timo...@koolin.ru Blog: http://timofey.koolin.ru -- 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.
