I've been taking a look at how riakc_obj is used in the erlang PBC
client after the issue of updating metadata was brought up by Mikl
Kurkov a few weeks ago.
The typical use case for the library is to get some data from the
server, and then sometimes modify it/write it back again. With the
current riakc_obj you have to set both the metadata and the value for
update or data will be lost. I've changed the library so that if there
are no siblings, updating the value or the metadata will leave the other
intact. If there are siblings you can base the result on one of them
using the new riakc_obj:select_sibling/2 call. The library also throws
descriptive atoms rather than badmatch when you try and use calls that
only work for objects without siblings.
Here's an example of updating links under the new API (before you would
have had to add an additional step of retrieving the value from O1 and
re-setting it in O2).
{ok, Pid} = start_link(Ip, Port),
O0 = riakc_obj:new(<<"b">>, <<"k">>, <<"d">>),
{ok, O1} = riakc_pb_socket:put(Pid, O0, [return_body]),
M1 = riakc_obj:get_metadata(O1),
M2 = dict:store(?MD_LINKS, [{{<<"b">>, <<"k1">>},
<<"t1">>}], M1),
O2 = riakc_obj:update_metadata(O1, M2),
riakc_pb_socket:put(Pid, O2)
I plan to push the changes into the main repo in a few days. To give
people a chance to play with them ahead of time I've forked the repo here
http://bitbucket.org/jon_meredith/riak-erlang-client-updobj
Let me know if anybody has concerns/feedback about the change.
--Jon.
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