Difference between revisions of "Round"
From NoSQLZoo
m |
|||
| Line 16: | Line 16: | ||
</pre> | </pre> | ||
{{TopTenTips}} | {{TopTenTips}} | ||
| − | Rounding is easy inside a <code>MapReduce</code> as it is possible to use the <code>Math</code> object provided by JavaScript. | + | Rounding is easy inside a <code>MapReduce</code> as it is possible to use the <code>Math</code> object provided by JavaScript.<br/> |
| − | At the time of writing the <code>aggregation()</code> method has no rounding functions, though it is still doable. | + | More information on <code>Math</code> can be found [https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Global_Objects/Math here].<br/><br/> |
| + | At the time of writing the <code>aggregation()</code> method has no rounding functions, though it is still doable with <code>$mod</code> and <code>$multiply</code>, as shown [http://www.kamsky.org/stupid-tricks-with-mongodb/rounding-numbers-in-aggregation-framework here] by the lead project manager at MongoDB<br/>. | ||
| + | |||
<div class='extra_space' style='width:1em; height:20em;'></div> | <div class='extra_space' style='width:1em; height:20em;'></div> | ||
<div class=q data-lang="py3">MapReduce | <div class=q data-lang="py3">MapReduce | ||
| Line 29: | Line 31: | ||
out={"inline":1}, | out={"inline":1}, | ||
) | ) | ||
| − | |||
pp.pprint( | pp.pprint( | ||
temp["results"] | temp["results"] | ||
) | ) | ||
| + | </pre> | ||
| + | </div> | ||
| + | |||
| + | <div class=q data-lang="py3">Aggregate | ||
| + | <pre class=def> | ||
| + | from bson.code import Code | ||
| + | pp.pprint(list( | ||
| + | db.world.aggregate([ | ||
| + | {"$limit": 1} | ||
| + | {"$match":{"area":{"$ne":0},"continent":"Asia"}}, | ||
| + | ]) | ||
| + | )) | ||
| + | |||
</pre> | </pre> | ||
</div> | </div> | ||
Revision as of 13:30, 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 $multiply, as shown here by the lead project manager at MongoDB
.
MapReduce
from bson.code import Code
temp = db.world.map_reduce(
query={"population":{"$ne":None}},
limit=1,
map=Code("function(){emit(this.name, this.population)}"),
reduce=Code("function(key, values){return Math.round(values/1000000)}"),
out={"inline":1},
)
pp.pprint(
temp["results"]
)
Aggregate
from bson.code import Code
pp.pprint(list(
db.world.aggregate([
{"$limit": 1}
{"$match":{"area":{"$ne":0},"continent":"Asia"}},
])
))