time.Time being stored as string instead of date (via interface{})

Kris Runzer

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Mar 14, 2016, 6:23:10 PM3/14/16

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Hello,

I have the following structs:

type Record struct {
	RecordID      string     `json:"recordID" bson:"_id"`
	CreatedOn     time.Time  `json:"createdOn" bson:"created_on"`
	LastUpdatedOn time.Time  `json:"lastUpdatedOn" bson:"last_updated_on"`
	Kind          Kind       `json:"kind" bson:"kind"`
	Data          RecordData `json:"data" bson:"data"`
}
// RecordData is a map of typed-backed key-values for a Record
type RecordData map[string]TypedValue

// SetString adds a new key with a string value
func (d RecordData) SetString(name, value string) {
	d[name] = TypedValue{Type: ValueTypeString, Value: value}
}

// SetNumber adds a new key with a float64 value
func (d RecordData) SetNumber(name string, value float64) {
	d[name] = TypedValue{Type: ValueTypeNumber, Value: value}
}

// SetDate adds a new key with a time.Time value
func (d RecordData) SetDate(name string, value time.Time) {
	d[name] = TypedValue{Type: ValueTypeDate, Value: value}
}

// TypedValue bundles a interface{} with a ValueType
type TypedValue struct {
	Type  ValueType   `json:"type" bson:"type"`
	Value interface{} `json:"value" bson:"value"`
}

// ValueType specifies the type of a TypedValue
type ValueType string

const (
	// ValueTypeString specifies the Value is of type String
	ValueTypeString ValueType = "string"
	// ValueTypeNumber specifies the Value is of type float64
	ValueTypeNumber ValueType = "number"
	// ValueTypeDate specifies the Value is of type time.Time
	ValueTypeDate ValueType = "date"
)

If I store the following struct:

rd := ps.RecordData{}
rd.SetDate("status_date", time.Now())
rd.SetString("status_severity", "asdf")
rd.SetNumber("status_codes", 1123.0)

I get the following in mongo:

"status_date" : {
    "type" : "date", 
    "value" : "2016-03-14T15:13:55.5802835-07:00"  // I would expect this to be an ISODate()
}, 
"status_severity" : {
    "type" : "string", 
    "value" : "asdf"
}, 
"status_codes" : {
    "type" : "number", 
    "value" : 1123.0
}

Here is the mgo operation doing the upsert:

func (s *store) Upsert(id string, kind spec.Kind, data spec.RecordData) (response spec.Record, err error) {
	s.mgoSearchHandler(func(db *mgo.Database) {
		now := time.Now()

		set := bson.M{
			"last_updated_on": now,
		}

		for key, val := range data {
			set["data."+key] = val
		}

		change := mgo.Change{
			ReturnNew: true,
			Upsert:    true,
			Update: bson.M{
				"$set": set,
				"$setOnInsert": bson.M{
					"_id":        id,
					"created_on": now,
					"kind":       kind,
				},
			},
		}

		_, err = db.C(cSearchRecords).FindId(id).Apply(change, &response)
	})

	return response, err
}

Is there something I am missing when working with interface{} that is causing this date to be a string instead of a ISODate()? Is my storing method the culprit (type information is being lost somewhere)?
)

Thank you,

Kris

David Marchbanks

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Mar 15, 2016, 7:40:13 AM3/15/16

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The same happens if you Marshall it into JSON. If you wanted it to come out differently, I believe you would need to write your own type with a Marshall.

Gustavo Niemeyer

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Mar 15, 2016, 9:12:19 AM3/15/16

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Hi Kris,

Your expectation is correct.. it should indeed be written into the database as a date/time value, and in my local tests it actually does that fine.

I suggest trying to reduce your code to a simpler self-contained example. You'll probably find the problem on the way.

To ensure there are no obvious bugs, I did the same here:

https://gist.github.com/niemeyer/94c812a57b1c1f20969f

Here is what gets written into the database:

> db.somevalues.find()

{ "_id" : ObjectId("56e8071ceb98a01a0f8db3a8"), "value" : ISODate("2016-03-15T12:59:08.295Z") }

> db.morevalues.find()

{ "_id" : 42, "field" : { "value" : ISODate("2016-03-15T12:59:08.296Z") } }

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Gustavo Niemeyer

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Mar 15, 2016, 9:19:12 AM3/15/16

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It happens in json because there's no native way to represent times and dates there.

BSON has a native type for those, though, and mgo's bson package supports it well. It should be stored exactly as expected in that case.

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