And this time, to the list as well :$
On 6 Oct 2011, at 10:22, Roland Karlsson wrote:
> Maybe my question below was not clear enough.
>
> I wonder why get_index() returns a list
> of lists (containing bucket/key pairs), when mapred()
> wants a list of tuples (containing bucket/key pairs).
> Looks like an unnecessary conversion by the user too me.
When you call get_index from the riak-erlang-client you are in fact running an
m/r operation. The input is an index query. The riak-erlang-client specifies a
reduce phase of riak_kv_mapreduce:reduce_identity/2, so you get back the output
from that (a list of [b,k] lists).
The Java client takes a different approach and has a reduce function that just
returns the keys, in a list. This is to provide parity with the output of the
HTTP API (which returns the JSON {"keys": ["k1", "k2"]})
If you wish, you can run an m/r job with an index input and subsequent
map/reduce phases to ensure the output is the shape you want it to be.
get_index() is just a convenience function for one such m/r job.
Cheers
Russell
>
> /Roland
>
>
>
>
> ----- Original Message -----
> From: "Roland Karlsson" <[email protected]>
> To: [email protected]
> Sent: Wednesday, October 5, 2011 4:33:17 PM
> Subject: Re: Secondary Index ??
>
> Thanx - now it works!
>
> Your explanations were very good.
>
> I also found I had to change from bitcask to eleveldb.
>
> I added one object with the same index and then I got the answer
>
> {ok, [[<<"persons">>,<<"kenny">>],[<<"persons">>,<<"bosse">>]]}
>
> Hmmm ... why is it a list in a list?
>
> /Roland
>
>
>
>
> ----- Original Message -----
> From: "Russell Brown" <[email protected]>
> To: "Roland Karlsson" <[email protected]>
> Cc: [email protected]
> Sent: Wednesday, October 5, 2011 3:12:04 PM
> Subject: Re: Secondary Index ??
>
>
> On 5 Oct 2011, at 13:45, Roland Karlsson wrote:
>
>> Hi,
>>
>> I might not look hard enough - but I cannot find how to use
>> the secondary indices from the riakc erlang client interface.
>> No example and no manual.
>
> Ooops, we'll get on that.
>
>>
>> I need a simple example how to write an indexed object
>> and also a simple example how to look it up via the index.
>>
>> This is my own try to write and lookup an object
>> It does not work :)
>
> Doesn't work crash or doesn't work, you get {ok, []} when you query the index?
>
>>
>> ----------------------------------------------------------
>> write_index(Pid) ->
>>
>>
>>
>> Bucket = <<"persons">>,
>> Key = <<"bosse">>,
>> Index = {<<"lives">>, <<"sumatra">>},
>
> Indexes should have a suffix of either _bin for binary or _int for integer.
>
>> Obj = riakc_obj:new(Bucket, Key, <<"1949">>),
>> Meta = dict:store(?MD_INDEX, Index, dict:new()),
>
> Index should be a list. If it *was* in a list you would have got an error
> {error,<<"{precommit_fail,[{unknown_field_type,<<\"lives\">>}]}">>} on put.
>
>> Obj2 = riakc_obj:update_metadata(Obj, Meta),
>> riakc_pb_socket:put(Pid, Obj2).
>> ----------------------------------------------------------
>> read_index(Pid) ->
>> Bucket = <<"persons">>,
>> Index = <<"lives">>,
>
> Again, the suffix. or you'll get
> {error,<<"{inputs,[{unknown_field_type,<<\"lives\">>}]}">>} when you do that
> get_index.
>
>> IndexKey = <<"sumatra">>,
>> riakc_pb_socket:get_index(Pid, Bucket, Index, IndexKey).
>>
>>
>> ----------------------------------------------------------
>
> Do _all_ that and I get {ok,[[<<"persons">>,<<"bosse">>]]} as the output from
> get_index.
>
> We'll get those docs updated.
>
> Cheers
>
> Russell
>>
>>
>> /Roland
>>
>> _______________________________________________
>> riak-users mailing list
>> [email protected]
>> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
>
>
> _______________________________________________
> riak-users mailing list
> [email protected]
> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
>
> _______________________________________________
> riak-users mailing list
> [email protected]
> http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
_______________________________________________
riak-users mailing list
[email protected]
http://lists.basho.com/mailman/listinfo/riak-users_lists.basho.com
