I'm not sure how much locality helps, but putting entities in a group for performance sounds like it could go wrong, depending on your data. Writes to entities within a group are serialized so having too many within in a single group can seriously hurt performance.
The API doc has some good hints: * Only use entity groups when they are needed for transactions * A good rule of thumb for entity groups is that they should be about the size of a single user's worth of data or smaller (from http://code.google.com/appengine/docs/python/datastore/keysandentitygroups.html) I think the scalable apps talk has some detail on this as well (and it's definitely worth watching anyway): http://sites.google.com/site/io/building-scalable-web-applications-with-google-app-engine cheers Michael On Feb 10, 11:26 pm, Michael Hart <[email protected]> wrote: > Not quite right - I think the "faster" property refers to the fact > that reads/writes can happen in parallel (because they're split over > multiple machines), not because of the actual geographical location of > the servers (not that this wouldn't help as well, but I don't believe > GAE currently has support for specifying geographical data location) > > I could be wrong though. > > On 11/02/2009, at 1:43 AM, Big Stu wrote: > > > > >> It also benefits from locality. Entity groups are stored close > >> together (needed to make transactions fast), which is why lots of > >> small entity groups makes the overall application faster (because > >> they > >> can be spread out). If you do a bunch of processing on groups of > >> entities in a single request then you can put them in a entity group, > >> which should make that processing faster because they will be kept > >> close. > > >> Dave. > > > I don't quite have my head wrapped around the entity group thing > > either. The transaction part I get...other benefits I don't quite get > > yet. If I were to build an app for managing dollar store inventory or > > something like that would I want to make all the data related to a > > particular store part of the same entity group? So that the data for > > a store in Toronto is part of one group, and the data for Vancouver is > > part of another, and then as far as teh datastore and access times are > > concerned the storage of the datasets will be best suited to the > > geography of the situation? Am I getting this right? > > > Thanks. > > > Stu --~--~---------~--~----~------------~-------~--~----~ You received this message because you are subscribed to the Google Groups "Google App Engine" group. To post to this group, send email to [email protected] To unsubscribe from this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/google-appengine?hl=en -~----------~----~----~----~------~----~------~--~---
