Auto-increment in MongoDB with CodeIgniter Alex Bilbie library - php

Question

First of all, sorry for my english and I'm beginning to study MongoDB. :)
I'm trying to insert a record using the CI library to MongoDB (https://github.com/alexbilbie/codeigniter-mongodb-library/tree/v2).
The insert works perfectly, but I can't insert using the recommended function to auto-increment getNextSequence (http://docs.mongodb.org/manual/tutorial/create-an-auto-incrementing-field/).
I tried the following ways without success.
Controller:
$data = array('_id' => 'getNextSequence("myid")',
'name' => 'Test '.time(),
'email' => 'test#test.com');
$this->default_model->add($this->collection, $data);
Model:
function add($collection, $data){
return $this->mongo_db->insert($collection, $data);
}
This returns the string 'getNextSequence("relatoriosid")' as the "_id".
I also tried used the command function, like this:
Controller:
$query = 'db.collection.insert({_id: getNextSequence("myid"), name: "Test '.time().'"});';
$ret = $this->default_model->execute($query);
var_dump($ret);
Model:
function execute($query){
return $this->mongo_db->command($query);
}
This way, returns the error:
["errmsg"]=> string(136) "exception: JavaScript execution failed: ReferenceError: getNextSequence is not defined near 'quence("myid"), name: "Teste 1374' "
["code"]=> int(16722)
["ok"]=> float(0)
Has anyone implemented something similar?
Thanks in advance!

Answer 1

I have implemented once mongoDB in one of my project.
I had faced similar problem. But one important thing i remember that we can not modify _id. Its MongoDB inbuilt properly. Neither its good to have the auto-increament in MongoDB because you need to implement that manually.
I will recommend that have another column in structure, you can call it anything, which will be virtual unique/primary key for you, lets say that column name is data_id.
$data = array('data_id' => md5(timestamp() . "<your string>"),
'name' => 'Test '.time(),
'email' => 'test#test.com');
if we check the documentation, is specified that Generally in MongoDB, you would not use an auto-increment pattern for the _id field, or any field, because it does not scale for databases with large numbers of documents. Typically the default value ObjectId is more ideal for the _id. Here i am referring to this link.
Even on the same link, its specified that getNextSequence() we need to write it. Its not inbuilt function.
Hope this helps you.

Answer 2

I got that problem too here is my solution.
Add this function to appflow\application\libraries
public function getNextSequence($name = ""){
if (empty($name))
{
show_error("In order to retrieve documents from MongoDB, a collection name must be passed", 500);
}
try{
$collection_1 = 'counters';
$collection = $this->db->{$collection_1};
$result = $collection->findAndModify(
['_id' => $name],
['$inc' => ['seq' => 1]],
['seq' => true],
['new' => true, 'upsert' => true]
);
if (isset($result['seq']))
{
return $result['seq'];
}
else
{
return false;
}
}
catch (MongoCursorException $e)
{
if(isset($this->debug) == TRUE && $this->debug == TRUE)
{
show_error("MongoDB query failed: {$e->getMessage()}", 500);
}
else
{
show_error("MongoDB query failed.", 500);
}
}
}
This is the way to use.
$nextID = $this->mongo_db->getNextSequence("maindata_child");
$this->mongo_db->where(array('_id'=>$mongo_id))->push('maindata_child', array('id'=>$nextID,'data'=>$maindata_child))->update('main_data');
and don't forget to add collection "counters".
db.counters.insert(
{
_id: "userid",
seq: 0
}
)
PS. I'm use this library https://github.com/bcit-ci/CodeIgniter/wiki/Using-MongoDB-in-Codeigniter
Reference for solution : http://tbsmc.com/a/mwbwswmm-mongodb-how-to-insert-record-using-autoincrement-functionality.html