Mongodb/PHP How to insert in nested array if not exist?

Question

The contents of my collection are in this form,

{ "_id" : ObjectId("50535036381ef82c08000002"),"source_references" : [
    {
            "_id" : ObjectId("50535036381ef82c08000001"),
            "name" : "abc",
            "key" : "123"
    }]
}

Now I want to insert another array in the "source_references" if the name and key does not exist in the nested array else don't insert. Here is the result I want,

{ "_id" : ObjectId("50535036381ef82c08000002"),"source_references" : [
    {
            "_id" : ObjectId("50535036381ef82c08000001"),
            "name" : "abc",
            "key" : "123"
    }
    {
            "_id" : ObjectId("50535036381ef82c08000003"),
            "name" : "reuters",
            "key" : "139215"
     }]
}

Here is what I've tried :

$Update_tag = array('$addToSet' => array("source_references.$" => array("name" => "reuters", "key" => $r_id)));
$mycollection->update(array("_id" => $id), $Update_tag);

But I am not able to insert another array inside the nested array. Also I want to create the "_id" field(inside nested array) only if new array inserted in source_references.

Where I am going wrong? Hope I am clear with my question.

Are you getting any error messages or just the wrong result? — Joachim Isaksson
– Joachim Isaksson, Commented Sep 15, 2012 at 6:40
I am not getting any error message. simply updation doesn't take place. @JoachimIsaksson — user1518659
– user1518659, Commented Sep 15, 2012 at 6:43
A couple of things to check first; you're spelling soruce_references.$ wrong when creating the array, and you have duplicate _id's (reuters & the root) in the expected result. — Joachim Isaksson
– Joachim Isaksson, Commented Sep 15, 2012 at 6:53
Do you need the embedded _id field in the source_references array if you are already assuming that (name + key) will be unique? — Stennie
– Stennie, Commented Sep 15, 2012 at 6:59
@JoachimIsaksson thats not an issue. I manually changed it. I am asking how to insert in such a scenario — user1518659
– user1518659, Commented Sep 15, 2012 at 7:24

Thomas · Accepted Answer · 2012-09-15 13:33:28Z

2

This is tricky because of the unique key that each of the sub-documents has. Therefore, you can't use $elemMatch to check if the key/name pair already exists.

If you're running mongodb 2.2, you can use the aggregation framework to $unwind the nested array, then $match for the key/name pair and insert the new element only if your search returned empty.

This is the php code:

<?php

// connect
$m = new Mongo('localhost:27017');

// select a database and collection
$db = $m->test;
$collection = $db->coll;

// sub-doc to insert if key/name pair doesn't exist
$doc = array('key'=>'12345', 'name' => 'abcde');

// aggregation command (can use $collection->aggregate for driver version 1.3.0+)
$cursor = $db->command(array('aggregate' => 'coll', 'pipeline' => array(
    array('$unwind'=>'$source_references'),
    array('$match' => array('source_references.name' => $doc['name'], 
                            'source_references.key' => $doc['key']))
)));

// if sub-doc doesn't exist, insert into main doc with this objectId
$objectId = '50535036381ef82c08000002';

if (count($cursor['result']) == 0) {
    // insert document with a new ObjectId (MongoId)
    $update_tag = array('$addToSet' => array("source_references" => array("_id" => new MongoId(), "name" => $doc['name'], "key" => $doc['key'])));
    $collection->update(array("_id" => new MongoId($objectId)), $update_tag);
} 

?>

answered Sep 15, 2012 at 13:33

Thomas

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1 Comment

user1518659 Over a year ago

before moving further thanks for your answer. Can you please elaborate your answer more so that I can understand a bit more? Does this command works only with mongo-db 2.2? .. because i dont have mongodb-2.2 running.

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