Преобразовать даты с $ project в MongoDB

Question

Я получаю сообщение об ошибке при попытке изменить поле даты в моей коллекции.

Это схема, и я хотел бы, чтобы изменить sent поле, которое хранит даты:

> db.complaints.findOne() 
{ 
    "_id" : ObjectId("55e5990d991312e2c9b266e3"), 
    "complaintID" : 1388734, 
    "product" : "mortgage", 
    "subProduct" : "conventional adjustable mortgage (arm)", 
    "issue" : "loan servicing, payments, escrow account", 
    "subIssue" : "", 
    "state" : "va", 
    "ZIP" : 22204, 
    "submitted" : "web", 
    "received" : "2015-05-22", 
    "sent" : "2015-05-22", 
    "company" : "green tree servicing, llc", 
    "response" : "closed with explanation", 
    "timely" : "yes", 
    "disputed" : "" 
} 

Это запрос, и сообщение об ошибке я получаю:

db.complaints.aggregate([ 
{$project: 
    {_id:0, 
    sent: 1, 
    Year:{$year:"$sent"}, 
    Month: {$month:"$sent"}, 
    Day: {$dayOfMonth: "$sent"}, 
    product : 1}}, 

]) 
> db.complaints.aggregate([ 
... {$project: 
... {_id:0, 
... sent: 1, 
... Year:{$year:"$sent"}, 
... Month: {$month:"$sent"}, 
... Day: {$dayOfMonth: "$sent"}, 
... product : 1}}, 
... 
... ]) 
assert: command failed: { 
    "errmsg" : "exception: can't convert from BSON type String to Date", 
    "code" : 16006, 
    "ok" : 0 
} : aggregate failed 
Error: command failed: { 
    "errmsg" : "exception: can't convert from BSON type String to Date", 
    "code" : 16006, 
    "ok" : 0 
} : aggregate failed 
at Error (<anonymous>) 
at doassert (src/mongo/shell/assert.js:11:14) 
at Function.assert.commandWorked (src/mongo/shell/assert.js:254:5) 
at DBCollection.aggregate (src/mongo/shell/collection.js:1278:12) 
at (shell):1:15 
2015-09-12T13:16:22.876+0100 E QUERY Error: command failed: { 
    "errmsg" : "exception: can't convert from BSON type String to Date", 
    "code" : 16006, 
    "ok" : 0 
} : aggregate failed 
at Error (<anonymous>) 
at doassert (src/mongo/shell/assert.js:11:14) 
at Function.assert.commandWorked (src/mongo/shell/assert.js:254:5) 
at DBCollection.aggregate (src/mongo/shell/collection.js:1278:12) 
at (shell):1:15 at src/mongo/shell/assert.js:13 
> db.complaints.aggregate([ 
... {$project: 
... {_id:0, 
... sent: 1, 
... Year:{$year:"$sent"}, 
... Month: {$month:"$sent"}, 
... Day: {$dayOfMonth: "$sent"}, 
... product : 1}}, 
... 
... ]) 
assert: command failed: { 
    "errmsg" : "exception: can't convert from BSON type String to Date", 
    "code" : 16006, 
    "ok" : 0 
} : aggregate failed 
Error: command failed: { 
    "errmsg" : "exception: can't convert from BSON type String to Date", 
    "code" : 16006, 
    "ok" : 0 
} : aggregate failed 
at Error (<anonymous>) 
at doassert (src/mongo/shell/assert.js:11:14) 
at Function.assert.commandWorked (src/mongo/shell/assert.js:254:5) 
at DBCollection.aggregate (src/mongo/shell/collection.js:1278:12) 
at (shell):1:15 
2015-09-12T13:21:08.767+0100 E QUERY Error: command failed: { 
    "errmsg" : "exception: can't convert from BSON type String to Date", 
    "code" : 16006, 
    "ok" : 0 
} : aggregate failed 
at Error (<anonymous>) 
at doassert (src/mongo/shell/assert.js:11:14) 
at Function.assert.commandWorked (src/mongo/shell/assert.js:254:5) 
at DBCollection.aggregate (src/mongo/shell/collection.js:1278:12) 
at (shell):1:15 at src/mongo/shell/assert.js:13 
> 

Answer 1

Вы можете используйте только операторы даты, такие как $year со значениями, которые имеют тип данных BSON Date. Значение Вашего sent месторождения является строкой, так что вам нужно использовать $substr разделить строку даты на позиции вместо:

db.complaints.aggregate([ 
{$project: 
    {_id: 0, 
    sent: 1, 
    Year: {$substr: ["$sent", 0, 4]}, 
    Month: {$substr: ["$sent", 5, 2]}, 
    Day: {$substr: ["$sent", 8, 2]}, 
    product: 1}} 
]) 

Результат:

{ 
"product" : "mortgage", 
"sent" : "2015-05-22", 
"Year" : "2015", 
"Month" : "05", 
"Day" : "22" 
}