On Mon, Jan 19, 2009 at 8:24 PM, Jeff Hinrichs - DM&T
<[email protected]> wrote:
>
>
> On Mon, Jan 19, 2009 at 6:25 PM, Paul Davis <[email protected]>
> wrote:
>>
>> On Mon, Jan 19, 2009 at 7:15 PM, Jeff Hinrichs - DM&T
>> <[email protected]> wrote:
>> > Using couchdb-python 0.5 and couchdb 0.9.0a735191-incubating
>> >
>> > I am working on a "rosetta stone" for javascript and python views. (nothing
>> > like rewriting in a different language to lean something<g>) I've worked
>> > though the simple map only views. I then did a simple reduce(keys,vals)
>> > which worked out fine. But I am stumped on rereduce when the function
>> > signature includes keys,vals,rereduce. I've been trying to work through
>> > the
>> > js code from "Top N Tags" from the snippets page,
>> > http://wiki.apache.org/couchdb/View_Snippets
>> >
>> > In particular, I am confused as to what is passed to the rereduce function
>> > when rereduce=True. The javascript is returning a complex structure
>> > instead
>> > of a simple scalar, I see that it has to do with getting state back from a
>> > previous reduce operation, but I'm confused. The unpacking of the previous
>> > results, I think has me befuddled ;(
>> >
>>
>> The reduce function is always returning a structure of the form:
>>
>> {
>> "tag1": N1,
>> "tag2": N2,
>> ...
>> }
>>
>> When you get to rereduce=true, then the values array is an array of
>> the structures that your code needs to combine.
>>
>> And for berevity, the last bit of code outside the if statement is
>> just discarding all tags below the top N so that the growth of data
>> doesn't exceed the log(num_rows) rule.
>>
>> HTH,
>> Paul Davis
>>
> That make sense from what I am reading. thanks.
> Any idea about the python view server from couchdb-python? The values tuple
> being returned works just fine however, the keys tuple, which appears to be a
> tuple of tuples is causing my reduce function to fail silently whenever I try
> to access an element by index.
>
> keys looks like [[tag, object_id],[tag, object_id],...]
>
> However when I try to access keys[0] (should be [tag, object_id]) or
> keys[0][0] (should be 'tag') my reduce script silently fails. If I just
> ignore tags and sum the values in a simple map/reduce I get the correct
> counts as simple vectors or atleast the same answer as the javascript
> equivalent. I'm hoping CMLenz will join the discussion or someone point me
> in the proper direction.
>
> Regards,
>
> Jeff
Ok, answering my own post -- you bang on your keyboard long enough and
you just might keep up with the monkeys<g>
I'm getting closer --
def reduce(keys,vals,rereduce):
tags = {}
if not rereduce:
for i in range(len(keys)):
tags[keys[i][0]] = tags.get(keys[i][0],0) + vals[i]
else:
tags = vals[0]
for i in range(1,len(vals)):
return vals
#tags[val[i][0]] += tags.get(val[i][0],0) + val[i][1]
return tags
get's me partially reduced to:
-Key- - Value-
"cool" {cool: 49}
"couchdb" {couchdb: 46}
"hopeful" {hopeful: 1}
"hot" [{hot: 30}, {hot: 38}]
"neat" {neat: 50}
"python" [{python: 25}, {python: 26}]
I've just go to do the proper thing with the lists of values for those
tags like hot and python. I'm off for tonight and I'll finish up in
the morning. I just didn't want someone wasting their time answering
a question that I've already muddle my way through -- map &
map/reduce is a wiki topic but rereduce is a topic by itself ;)
keeping-up-with-the-shakespearian-monkeys-mostly'ly
Jeff
