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Type:
Improvement
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Resolution: Unresolved
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Priority:
Major - P3
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None
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Affects Version/s: 2.2.0-rc0, 2.2.0-rc1
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Component/s: Aggregation Framework
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Environment:Linux, Mac OSX
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Query Execution
Add an accumulator/expression that takes dates and returns their average (could be called $avgDate).
Original description:
When using aggregation framework $avg on an ISODate in mongo shell I get the following error message:
{
"errmsg" : "exception: can't convert from BSON type 2 to double",
"code" : 16005,
"ok" : 0
}
Here's my setup. Collection data:
> db.sys_user.find({}, {sys_created_on:1}).limit(3)
{ "_id" : ObjectId("502a95d4c2e6f4d8ffbbef21"), "sys_created_on" : ISODate("2012-02-18T03:04:49Z") }
{ "_id" : ObjectId("502a95d4c2e6f4d8ffbbef22"), "sys_created_on" : ISODate("2012-02-18T03:04:49Z") }
{ "_id" : ObjectId("502a95d4c2e6f4d8ffbbef23"), "sys_created_on" : ISODate("2012-02-18T03:04:49Z") }
This errors:
> db.sys_user.aggregate([ { $group: {_id:null, max:{$max:"$sys_created_on"}, min:{$min:"$sys_created_on"}, avg:{$avg:"sys_created_on"}} }, { "$project" : { "_id" : 0 , "max": 1, "min": 1, "avg": 1}} ])
{
"errmsg" : "exception: can't convert from BSON type 2 to double",
"code" : 16005,
"ok" : 0
}
$min, $max work fine:
> db.sys_user.aggregate([ { $group: {_id:null, max:{$max:"$sys_created_on"}, min:{$min:"$sys_created_on"}} }, { "$project" : { "_id" : 0 , "max": 1, "min": 1}} ])
{
"result" : [
{
"max" : ISODate("2012-03-21T05:13:21Z"),
"min" : ISODate("2004-05-02T00:00:00Z")
}
],
"ok" : 1
}