get_metadata returns the metadata that was read from riak. But if allow_mult is true, and there is more than one sibling, then get_metadata throws the exception 'siblings'. You have to call get_metadatas to get a list with metadata for each sibling in that case.
get_update_metadata returns the metadata that is to be written for the object (if you were to call riakc_pb_socket:put at that point). The update metadata is either a single value set explicitly with riakc_obj:update_metadata, or if none was set, and there is only one sibling, then the default is the value of get_metadata. A related question: if I'm not using any user-specified metadata at all, but I do have allow_mult turned on, then how do I choose which metadata to write back to riak after resolving the conflict? Or could I just call update_metadata with an empty dict in that case? Right now, I have some conflict resolution code that uses the same default strategy as mochimedia's statebox_riak library, which arbitrarily chooses the first metadata. But this seems less than ideal: everything in the metadata is coming from riak, and some of it (e.g., last-modified timestamps) must be ignored when doing the update. So it seems like riak should be able to resolve the "metadata conflict" on its own: just prune all the metadata keys that aren't actually written, and then if the resulting pruned metadatas are identical, then there's no conflict. Or, if there is some reason why the user should prefer one metadata over another, then the client library should give the user some way to decide. Mike On Tue, Jun 12, 2012 at 11:25 AM, Andrew Berman <rexx...@gmail.com> wrote: > Can someone explain the difference between the get_update_metadata and > get_metadata functions in the Erlang PB Client for Riak? It's very > confusing... > > Thanks, > > Andrew > > _______________________________________________ > riak-users mailing list > riak-users@lists.basho.com > http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com > _______________________________________________ riak-users mailing list riak-users@lists.basho.com http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
