Create your own id with Mgo
I am currently starting with GoLang and MongoDB. I am writing a small web app, blog more specific (this is like the first webapp I write when I try new languages). Everything works fine with MGO, even if I had problems at first. But now I would like to access each blog post (articles will be referred to as posts to stick with my models) separately. I could use ObjectID in the url. But it's damn ugly. For example: mydomain.com/entries/543fd8940e82533995000002/
This is not convenient. I did a lot of research on the internet to find a suitable solution, because using any other database engine, I could just use the ID (and that would be fine).
Can anyone help me create a custom (public) ID that will automatically increment when I insert a new record and what can I use in the URL?
Here is my model code:
package models
import (
"time"
"labix.org/v2/mgo"
"labix.org/v2/mgo/bson"
)
type (
Entries []Entry
Entry struct {
ID bson.ObjectId `bson:"_id,omitempty"`
Title string `bson:"title"`
Short string `bson:"short"`
Content string `bson:"content"`
Posted time.Time `bson:"posted"`
}
)
// Insert an entry to the database
func InsertEntry(database *mgo.Database, entry *Entry) error {
entry.ID = bson.NewObjectId()
return database.C("entries").Insert(entry)
}
// Find an entry by id
func GetEntryByID(database *mgo.Database, id string) (entry Entry, err error) {
bid := bson.ObjectIdHex(id)
err = database.C("entries").FindId(bid).One(&entry)
return
}
// Retrieves all the entries
func AllEntries(database *mgo.Database) (entries Entries, err error) {
err = database.C("entries").Find(nil).All(&entries)
return
}
// Retrieve all the entries sorted by date.
func AllEntriesByDate(database *mgo.Database) (entries Entries, err error) {
err = database.C("entries").Find(nil).Sort("-posted").All(&entries)
return
}
// Counts all the entries.
func CountAllEntries(database *mgo.Database) (count int, err error) {
count, err = database.C("entries").Find(nil).Count()
return
}
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As you know, _id is a required field that is automatically populated by the driver when you don't install it. This is the behavior you have in your current application / code. You can find information about this type and its generation here: http://docs.mongodb.org/manual/reference/object-id/
However, you can create your own _id and set a value to anything that makes sense for your company.
This is why I don't understand the following statement:
I did a lot of research on the internet to find a suitable solution, because using any other database engine, I could just use the ID (and that would be nice).
You can use whatever value you want, as soon as it is unique to your collection.
About auto-increment MongoDB does not provide any auto-increment field, so you must implement it yourself and call the increment from your application.
For example, you create a new collection containing your "sequences / counters": (showing no shell commands)
{
_id : "entry",
sequence : 0
}
Then, when you need a new id for your document that you first updated, find and modify the document you created with a simple $ inc operation
var ret = db.counters.findAndModify(
{
query: { _id: "entry" },
update: { $inc: { seq: 1 } },
new: true
}
);
Then you can use the return value in the new document as _id.
This pattern is described here: http://docs.mongodb.org/manual/tutorial/create-an-auto-incrementing-field/
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