How can I search for the records filtering in a field that has an undefined value:
db.records.aggregate({
$match: {
myField: "undefined",
}
})
asked Jun 13, 2013 at 13:16
Alexander Abramovich
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3 Answers
Filter it by $type:6, (mongodb referece, note that this type marked as 'deprecated'):
db.records.aggregate({
$match: {
myField: {'$type':6},
}
})
1 Comment
Chris
Thanks for this. The accepted answer doesn't seem to actually answer the question but this does and is amazingly useful give that if you try to search for
undefined it tells you that you can't.If you want to filter out documents that have some fields missing, use the $exists operator.
This works on my machine :
> db.test.drop()
true
> db.test.insert( {'Hello':'World!', 'myField':42})
> db.test.insert( {'Hello again':'World!'})
> db.test.aggregate({'$match':{ 'myField':{'$exists':false} }})
{
"result" : [
{
"_id" : ObjectId("51b9cd2a6c6a334430ec0c98"),
"Hello again" : "World!"
}
],
"ok" : 1
}
The document that has myField present does not show in the results.
1 Comment
jimoleary
The $type operator is also available to search for fields with
null values (there's also a deprecated undefined type). This FAQ entry explains querying for nulls and/or missing fields (the same operators are available for the aggregation framework) . For example :db.test.aggregate({'$match':{ 'myField':{'$type':10} }}) would match documents that have a myField defined but its value is null.If you have fields that exist but are undefined you can search for them with null.
db.records.aggregate({
$match: {
myField: {$exists: true, $eq: null},
}
})
Comments
$exists? If possible, add a sample document and a regular query that would return it. Looking at your question,'undefined'is a string, just like'Hello, World!'.