Difference between revisions of "Round"
From NoSQLZoo
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<div class=q data-lang="py3">MapReduce | <div class=q data-lang="py3">MapReduce | ||
<pre class=def> | <pre class=def> | ||
− | |||
temp = db.world.map_reduce( | temp = db.world.map_reduce( | ||
− | query={" | + | query={"name":"United Kingdom"}, |
− | |||
map=Code("function(){emit(this.name, this.population)}"), | map=Code("function(){emit(this.name, this.population)}"), | ||
− | reduce=Code("function(key, values){return Math.round(values/1000000)}"), | + | reduce=Code("function(key, values){return values}"), |
+ | finalize=Code("function(key,values){return Math.round(values/1000000)}"), | ||
out={"inline":1}, | out={"inline":1}, | ||
) | ) | ||
Line 39: | Line 38: | ||
<div class=q data-lang="py3">Aggregate | <div class=q data-lang="py3">Aggregate | ||
<pre class=def> | <pre class=def> | ||
− | |||
pp.pprint(list( | pp.pprint(list( | ||
db.world.aggregate([ | db.world.aggregate([ | ||
− | {"$ | + | {"$match": {"name":"United Kingdom"}}, |
− | {"$ | + | {"$project":{ |
+ | "_id":1, "name":1, "population":{"$divide":["$population",1000000]} | ||
+ | }}, | ||
+ | {"$project":{ | ||
+ | "_id":0, "name":1, "population in millions":{"$divide":[ | ||
+ | {"$subtract":[ | ||
+ | {"$multiply":['$population',100]}, | ||
+ | {"$mod":[{"$multiply":['$population',100]}, 1]} | ||
+ | ]},100 | ||
+ | ]} | ||
+ | }} | ||
]) | ]) | ||
)) | )) | ||
− | |||
</pre> | </pre> | ||
</div> | </div> |
Revision as of 15:07, 26 July 2015
#ENCODING import io import sys sys.stdout = io.TextIOWrapper(sys.stdout.buffer, encoding='utf-16') #MONGO from pymongo import MongoClient client = MongoClient() client.progzoo.authenticate('scott','tiger') db = client['progzoo'] #PRETTY import pprint pp = pprint.PrettyPrinter(indent=4) #CODE from bson.code import Code
Rounding is easy inside a MapReduce
as it is possible to use the Math
object provided by JavaScript.
More information on Math
can be found here.
At the time of writing the aggregation()
method has no rounding functions, though it is still doable with $mod
and $multiply
, as shown here by the lead project manager at MongoDB
.
MapReduce
temp = db.world.map_reduce( query={"name":"United Kingdom"}, map=Code("function(){emit(this.name, this.population)}"), reduce=Code("function(key, values){return values}"), finalize=Code("function(key,values){return Math.round(values/1000000)}"), out={"inline":1}, ) pp.pprint( temp["results"] )
Aggregate
pp.pprint(list( db.world.aggregate([ {"$match": {"name":"United Kingdom"}}, {"$project":{ "_id":1, "name":1, "population":{"$divide":["$population",1000000]} }}, {"$project":{ "_id":0, "name":1, "population in millions":{"$divide":[ {"$subtract":[ {"$multiply":['$population',100]}, {"$mod":[{"$multiply":['$population',100]}, 1]} ]},100 ]} }} ]) ))