MongoDB find with key that starts with a string pattern - php

Question

I'm trying to fetch a mongodb data using PHP.
My Data is in the following format:
$document = $collection->findOne(
array('_id' => 'set1'),
array('projection' => array('_id' => 1,'data'=>1))
);
Result:
{
"_id": "set1",
"data": {
"IND": {
"2015-01": 0.6753404,
"2015-02": 1.0502269,
"2015-03": 1.0902269
},
"AUS": {
"2015-01": 0.6753404,
"2015-02": 1.0502269,
"2015-03": 1.0902269
},
"IND_123": {
"2015-01": 0.6753404,
"2015-02": 1.0502269,
"2015-03": 1.0902269
}
}
}
I am trying to fetch the output such that the result only has "IND" and "IND_123".
Is there a way to write the projection such that the result only provides "IND*"
The following provides only "IND"
$document = $collection->findOne(
array('_id' => 'set1'),
array('projection' => array('_id' => 1,'data.IND'=>1))
);

Answer 1

You can achieve it using an aggregation pipeline, like this:
db.collection.aggregate([
{
"$match": {
"_id": "set1"
}
},
{
"$project": {
data: {
"$arrayToObject": {
"$filter": {
"input": {
"$objectToArray": "$data"
},
"as": "item",
"cond": {
"$regexMatch": {
"input": "$$item.k",
"regex": "IND.*"
}
}
}
}
}
}
}
])
Playground link.
Here, we match the required document using $match. Then we, recompute the data field in $project, we first convert the data object to an array using $objectToArray, and filter all keys matching the pattern IND.* using $filter. Finally, we convert the filtered array back to an object using $arrayToObject.