mongodb update or insert sub-array

Question

ok, I need away to do the following

I have the mongo collect as

array (
  '_id' => new MongoId("50513d8338fc5de706000000"),
  'offers' => 
  array (
    '0' => 
    array (
      'minspend' => '50.00',
      'cashback' => '1.50',
      'percentage' => '0.03',
    ),
    '1' => 
    array (
      'minspend' => '100.00',
      'cashback' => '3.00',
      'percentage' => '0.03',
    ),
  ),
  'percentageTotal' => '0.06',
  'test' => new MongoInt32(1),
)

but lets say I want to update only this part

array (
        '0' => 
        array (
          'minspend' => '50.00',
          'cashback' => '1.50',
          'percentage' => '0.03',
        ),

what is the best way to change that part of the sub array without re-creating the whole collection of data in that array.

and is it possible to do something like this

array (
        '0' => 
        array (
'Offer_id'=> new MongoId(5715671561715),
          'minspend' => '50.00',
          'cashback' => '1.50',
          'percentage' => '0.03',
        ),

)

Thomas · Accepted Answer · 2012-09-19T06:33:14.657

You can use $set together with dot-notation to specify which element of an array you want to update:

$collection->update(
    array("_id" => new MongoId("50513d8338fc5de706000000")), 
    array("$set" => array("offers.0" => 
        array (
            'minspend' => '50.00',
            'cashback' => '1.50',
            'percentage' => '0.03',
        )
    ))
);

offers.0 refers to the 0th (= first) element in the array. If you want to update the second one, you would use offers.1 as the key.

For your second question, I'm assuming you want to add the MongoId to the sub-document. You can do that the same way, simply by adding 'Offer_id' => new MongoId(), before minspend. This will create a new unique MongoId and add it to the sub-document. If you want to add an existing MongoId instead, use new MongoId("...") and replace the ... with the 24 hexidecimal character long string.

If you already have an Offer_id and only want to change the offer that matches that id, you can use the positional $ syntax:

$collection->update(
    array("_id" => new MongoId("50513d8338fc5de706000000"),
          "offers.Offer_id" => new MongoId("5059637720dfeda164ec0fe7")), 

    array("$set" => array("offers.$" => 
        array (
            'minspend' => '50.00',
            'cashback' => '1.50',
            'percentage' => '0.03',
        )
    ))
);

You query for the document with the correct _id and additionally for the offers.Offer_id. In the update part of the command, you use offers.$ where $ will automatically match the correct sub-document that contains the Offer_id.

if i have the offers.[].offer_id can i use that to update the minspend etc? — RussellHarrower, Sep 18 '12 at 06:07
In that case, use the offer_id in the query as a second condition (querying for _id and offers.offer_id and use the $ sign as the positional argument. See here how the positional operator works: http://www.mongodb.org/display/DOCS/Updating#Updating-The%24positionaloperator — Thomas, Sep 18 '12 at 08:16
could you please explain this? with an example the documents dont really help — RussellHarrower, Sep 19 '12 at 03:24
sure, I've added it to the code example above. I hope this answers your question. — Thomas, Sep 19 '12 at 06:33

mongodb update or insert sub-array

1 Answers1