How to call mongodb server function inside update statement - mongodb-php

Question

Lets say there is an array defined as sub document.
User
first_name:"blah",
last_name: "blah",
scores [{score: 12},
{score: 13},
{score: 9},
{score: 14}]
Say I want to loop through this sub array inside the update statement and check if I need to add a new score. New score could be 8 or 16 if its 8 then nothing should be added, however if its 16 it should be added to the end of the list.
Is there is anyway to define javascript server side function and use it inside update statement, or there are other way of doing something like that? The important thing that operation has to be atomic.
Using php driver
public bool|array MongoCollection::update ( array $criteria , array $new_object [, array $options = array() ] )
How do I specify criteria to match those conditions that I have listed?

Answer 1

You can create a server-side javascript function, however the creators of mongo do not recommend this:
We do not recommend using server-side stored functions if possible.
If you need atomicity with complex logic, one approach with is to lock the document before working with it. You can achieve this with the findAndModify function. The basic gist of this is that you try to find your document as you normally would, with the additional criteria that locked = false. The modify part of this function would set locked = true.
db.people.findAndModify({
query: { name: "Andy", locked: false },
update: { locked: true },
});
You now are free to work with the document "atomically" When you write the changes back to your database, you set locked = false. Make sure you wrap your block in a try/catch/finally and ensure the document is unlocked in the finally block.
Note that if your operation is very simple (simply need to add a field to your list), then using findAndModify alone to update the document fields may be enough for what you need.
Edit: If you really want to use server-side functions here's an example from the PHP mongo documentation:
$response = $db->execute("function(x) { return x;}", array("input param"));
Here's how you could persist a function for later use (through the mongo shell)
db.system.js.save(
{ _id: "echoFunction",
value : function(x) { return x; }
}
)
Then later in PHP:
$response = $db->execute("echoFunction( 'test' )");
var_dump($response);
Edit2:
Your update function is much easier than I first understood. You simply need the following:
$db->update(
array("first_name" => "blah"),
array(
"$push" => array(
"scores" => array("score" => 16)
)
)
);
Edit2: Access your collection from inside a function
function push_score(id, score) {
//your logic here
//...
db.your_collection.update({_id: ObjectId(id), $push: {scores: {score: score}}})
}