I would like to use benchRun http://www.mongodb.org/display/DOCS/JS+Benchmarking+Harness on a query like this:
.find().sort({ last_date : 1 }).limit(1,
Is there a way to specify such a query in the "ops" JSON array? I couldn't see anything in the benchRun.cc source code, so I just wanted to check. Thanks for your help!
Currently, there is no way to use it for sort. It is "planned but not scheduled" according to the issue SERVER-5722.
Related
I am trying to execute 2 queries at the same time, for example, refer below:
db.getCollection('Test').find({'color':'red'},{'color':'yellow'});
Assume that color red is present in the one collection and yellow is present in another collection, but I am getting the response only from the first query.
Expectation:
1.If both the queries are present in any of the collection I should get both
responses.
2.If anyone of the query is invalid or element is not present in the collection,
I should not get any response.
Thanks in advance
Since you want to match existence of both values, use $all operator:
db.getCollection('Test').find({color:{$all:["red","yellow"]}})
Edit
I managed to get your output, but I think this could be simplified. I thought about different options and ended up in this query:
db.colors.aggregate([{
$facet:{
cond1:[{$match:{color:"red"}}],
cond2:[{$match:{color:"yellow"}}]
}},
{$project:{match1: "$cond1", match2:"$cond2" ,size1:{$size: "$cond1"},
size2:{$size: "$cond2"}}},
{$project:{result:{$cond:[{$and:[{$gte:["$size1",1]},{$gte:
["$size2",1]}]},{$concatArrays:["$match1","$match2"]},[]]}}}
])
I think there is something wrong with your question.
I think you are looking for something like this db.getCollection('Test').find({color: {$in: ['red','yellow']}});
I hope this will help.
like:
{id:4563214321,updateTime:long("124354354")}
there are always new collections enter the db, so I would like to always get latest updated documents aka the largest update time. how to design the shell script? thanks in advance.
You can use a combination of limit and sort to achieve this goal.
db.collectionName.find({}).sort({"updateTime" : -1}).limit(1)
This will sort all of your fields based on update time and then only return the one largest value.
I would recommend adding an index to this field to improve performance.
This is a repeated question, you can find an answer in this link
Using findOne in mongodb to get element with max id
use like this,
db.collection.find().sort({updateTime:-1}).limit(1).pretty()
as findOne you can do it with this syntax:
db.collection.findOne({$query:{},$orderby:{_updateTime:-1}})
I know that the ATTR function is used for aggregation, but can someone explain it in simple terms?
In the most simplest of terms, ATTR returns a value if it is unique, otherwise it returns "*". I think you'll find this link helpful with examples.
https://www.interworks.com/blog/tcostello/2014/05/15/attr-tableaus-attribute-function-explained
You cannot mix aggregate and non aggregate comparisons in tableau, you have to use ATTR, for e.g. if ATTR(segment) ='Corporate' then sum(sales)
ATTR is like using an already aggregated field for comparison with another aggregated field. Measures are taken as aggregated fields while dimension's aren't. If you have created a field which is already aggregated and still you want to use this field as measure it will be shown as ATTR as it cannot be further aggregated but is behaving like it has.
I'm using luamongo to query mongodb. I'm quite inexperienced with mongodb, and I'm having trouble figuring out how to specify the sorting/order for the query. I don't see anything specifically about sorting on the project's wiki, but I might be missing something.
Is there a way to do this, or do I need to manually sort the returned results?
Thanks!
From https://github.com/moai/luamongo/issues/14:
To sort a query: mongodb:query("database.collection", {query = {field=value}, orderby = {field = 1}})
I need to group and sort by date_published some documents stored on mongodb using pymongo.
the group part went just fine :) but when I'm addding .sort() to the query it keeps failing no matter what I tried :(
here is my query:
db.activities.group(keyf_code,cond,{},reduce_code)
I want to sort by a field called "published" (timestamp)
tried to do
db.activities.group(keyf_code,cond,{},reduce_code).sort({"published": -1})
and many more variations without any success
ideas anyone?
You can't currently do sort with group in MongoDB. You can use MapReduce instead which does support a sort option. There is also an enhancement request to support group with sort here.
Although MongoDB doesn't do what you want, you can always use Python to do the sorting:
result = db.activities.group(keyf_code,cond,{},reduce_code)
result = sorted(result, key=itemgetter("published"), reverse=True)