From my website client I am sending an API request to the backend Node.js server and finding a specific document by ID like so:
var ObjectID = require('mongodb').ObjectID;
db.collection('users').find({"_id": new ObjectID(req.body._id)})
Where req.body._id equals the entire ID string, such as '5d0381ad681a2a3aa1dc5872'
However I would prefer to send only the INC (ever incrementing value) portion of the string as the argument: 'c5872'
How should I find a specific document based on just the INC value? (I'm assuming the INC is unique)
Any help is greatly appreciated.
You can temporarily transform your _id using in a string to be able to use a regular expression :
db.users.aggregate([
{
$addFields: { id: { $toString: '$_id' } }
},
{
$match: { id: /c5872$/ }
}
])
A cleaner solution is to create the field directly with a substring to avoid using a regular expression :
db.users.aggregate([
{
$addFields: { id: { $substr: [{ $toString: '$_id' }, 19, 24] } }
},
{
$match: { id: 'c5872' }
}
])
https://docs.mongodb.com/manual/reference/operator/aggregation/addFields/ https://docs.mongodb.com/manual/reference/operator/aggregation/substr/
You could create an additional ID field and a unique index to ensure that indexed fields do not store duplicate values, but note that for a five hex string, we have "1,048,576" possible combinations (16 ^ 5 = 1048576).
Note: Using a regular expression could lead to a collection scan.
A regular expression is a "prefix expression" if it starts with a caret (^) or a left anchor (\A), followed by a string of simple symbols. For example, the regex /^abc.*/ will be optimized by matching only against the values from the index that start with abc.