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besides emit() in map(), can I simply omit this map-reduce cycle?
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λq  
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 More options Jul 11 2011, 11:57 pm
From: λq <lamb...@gmail.com>
Date: Tue, 12 Jul 2011 11:57:14 +0800
Local: Mon, Jul 11 2011 11:57 pm
Subject: besides emit() in map(), can I simply omit this map-reduce cycle?
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Hi guys,

I knew that mapReduce() has a query parameter, but in my case,

{
  'user': user1,
  'top-list': [
    {'score': score1, 'date': date1, 'app': app1},
    {'score': score4, 'date': date4, 'app': app4},
    {'score': score3, 'date': date3, 'app': app3},
  ]

}

I want to use mapReduce() to find the history position change of a
particular my_app

the query parameter can do the job, but IMHO it looks redundant because when
doing the map(), I have to iterate the 'top-list' array again.

Is there something like pass() or omit() besides the standard emit() in map
function? So mongodb could just skip this round of map-reduce and continue
next?


 
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Eliot Horowitz  
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 More options Jul 12 2011, 12:06 am
From: Eliot Horowitz <eliothorow...@gmail.com>
Date: Tue, 12 Jul 2011 00:06:01 -0400
Local: Tues, Jul 12 2011 12:06 am
Subject: Re: [mongodb-user] besides emit() in map(), can I simply omit this map-reduce cycle?
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I'm a bit confused by what you mean.
Is that a sample document that's in the collection?

What would the output look like?

2011/7/11 λq <lamb...@gmail.com>:


 
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λq  
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 More options Jul 12 2011, 12:16 am
From: λq <lamb...@gmail.com>
Date: Tue, 12 Jul 2011 12:16:21 +0800
Local: Tues, Jul 12 2011 12:16 am
Subject: Re: [mongodb-user] besides emit() in map(), can I simply omit this map-reduce cycle?
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{
  'user': user1,
  'day': '2011-07-09'
  'top-list': [
    {'score': score1, 'date': date1, 'app': app1},
    {'score': score2, 'date': date2, 'app': app2},
    {'score': score3, 'date': date3, 'app': app3},
  ]

},

{
  'user': user1,
  'day': '2011-07-10'
  'top-list': [
    {'score': score1, 'date': date1, 'app': app1},
    {'score': score3, 'date': date3, 'app': app3},
    {'score': score4, 'date': date4, 'app': app4},
  ]
},

{
  'user': user1,
  'day': '2011-07-11'
  'top-list': [
    {'score': score3, 'date': date3, 'app': app3},
    {'score': score4, 'date': date4, 'app': app4},
    {'score': score2, 'date': date2, 'app': app2},
  ]

},

Given app3, return a result like:

{'2011-07-09': 3, '2011-07-10': 2, '2011-07-11': 1}

app3 is at rank #3 place in 2011-07-09, raised to #1 and #1 in the following
days.

But in the collection, app3 is out of the 'top-list'array, so I do not want
the mapReduce() to process this document, yes just a 'query' parameter for
mapReduce() could filter that out, but since I already need to iterate the
whole 'top-list' array in the map() function, I think I don't need 'query'
parameter?

So can I skip a number of documents for a map() ?

2011/7/12 Eliot Horowitz <eliothorow...@gmail.com>


 
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Eliot Horowitz  
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 More options Jul 12 2011, 12:19 am
From: Eliot Horowitz <eliothorow...@gmail.com>
Date: Tue, 12 Jul 2011 00:19:21 -0400
Local: Tues, Jul 12 2011 12:19 am
Subject: Re: [mongodb-user] besides emit() in map(), can I simply omit this map-reduce cycle?
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The query would still be helpful if there are documents that don't
have app3 at all.
If all do, then the query isn't needed.

2011/7/12 ëq <lamb...@gmail.com>:


 
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λq  
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 More options Jul 12 2011, 12:24 am
From: λq <lamb...@gmail.com>
Date: Tue, 12 Jul 2011 12:24:29 +0800
Local: Tues, Jul 12 2011 12:24 am
Subject: Re: [mongodb-user] besides emit() in map(), can I simply omit this map-reduce cycle?
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Yes the 'query' parameter is helpful, but I think 'query' needs to lookup
the whole 'top-list' array or index, then I look them up again because I
need to find its position?

Some performance is wrong here. (I hope mongodb could just get the position
of the element in the array if there is already a 'query' parameter.)

On Tue, Jul 12, 2011 at 12:19 PM, Eliot Horowitz <eliothorow...@gmail.com>wrote:


 
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Eliot Horowitz  
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 More options Jul 12 2011, 1:11 am
From: Eliot Horowitz <eliothorow...@gmail.com>
Date: Tue, 12 Jul 2011 01:11:33 -0400
Local: Tues, Jul 12 2011 1:11 am
Subject: Re: [mongodb-user] besides emit() in map(), can I simply omit this map-reduce cycle?
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Correct - mongo won't do that for you.
You can open a feature request @ http://jira.mongodb.org

2011/7/12 λq <lamb...@gmail.com>:


 
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