Thanks guys, it really helps! I didn't know about protobuf - thought that u have massive key/value map (so it would be possible to just touch one key). Now it all make sense :)
On Oct 12, 1:22 pm, "Ikai Lan (Google)" <ika...@google.com> wrote: > Thanks Murph. That explanation was dead-on and I couldn't have written a > better one myself! > > You can't just update one "column". You're still thinking in RDBMS mode. > There is no concept of a column, since to update a property, we need to read > the entire entity, deserialize it (it's serialized as protobuf; at its > lowest layer BigTable is a key-value store), change the property, > reserialize the entire entity and write it. > > -- > Ikai Lan > Developer Programs Engineer, Google App Engine > plus.ikailan.com | twitter.com/ikai > > > > > > > > On Tue, Oct 11, 2011 at 2:38 PM, Murph <paul.j.mu...@googlemail.com> wrote: > > You can't update just a single property/attribute of an entity unless you > > already know the values for all of the others. If it's frequently updated, > > careful use of memcache may allow you to avoid the db.get, but otherwise you > > have to read it first. > > > An alternative, if you just have say 1 property/attribute which changes > > often would be to split the entity into two separate entity models, one with > > the relatively static data, and the other with the frequently changing > > data. The downside there, of course, is that you're going to have 2 db.get > > operations when you need all of it, instead of 1. > > > Internally, the datastore is entirely composed of (key, value) pairs, with > > a single (key,value) per entity (not counting indices, metadata, etc), and > > the SDK encodes/decodes those values into your entity models for you. They > > are actually encoded as protobufs, but there's nothing in the datastore's > > API to modify that data without reading it first. > > > -- > > You received this message because you are subscribed to the Google Groups > > "Google App Engine" group. > > To view this discussion on the web visit > >https://groups.google.com/d/msg/google-appengine/-/e6JrqffTES4J. > > > 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.
