Mongodb Java query for date range

I needed to find all the records in mongo db within two date ranges using Mongo Driver[3.4.0] for Java.

Example: I have books Collection.

{
    "_id" : ObjectId("5acb40d27d63b61cb002bafe"),
    "title" : "WingsOfFire",
    "pub-date" : ISODate("2013-10-02T00:00:00.000Z"),
    "rel-date" : ISODate("2013-11-02T00:00:00.000Z")
}

Like above I have 100s of documents.

I need to find all records wherein pub-date > rel-date.

I am using Mongo DB version 3.2.6

I tried to use $expr operator but it seems to work with only Mongo 3.6+

Not able find cleaner solutions for above requirement.

Please clarify.

回答1:

You might want to try $where-Operator:

db.books.find({ "$where": "this.pub-date > this.rel-date"});

回答2:

The MongoDB (prior to v3.4) shell command for your use case is:

db.collection.aggregate([
    {
        "$redact": {
            "$cond": [
                { "$gt": [ "$pub-date", "$rel-date" ] },
                "$$KEEP",
                "$$PRUNE"
            ]
        }
    }
])

Translating this command into Java you'll get:

MongoClient mongoClient = ...;

MongoCollection<Document> collection = mongoClient.getDatabase("...").getCollection("...");

List<Document> documents = collection.aggregate(Arrays.asList(
        new Document("$redact", new Document("$cond",
                Arrays.asList(new Document("$gt", Arrays.asList("$pub-date", "$rel-date")), "$$KEEP", "$$PRUNE"))
        ))).into(new ArrayList<>());

for (Document document : documents) {
    System.out.println(document.toJson());
}

Given a collection with these documents ...

{
    "_id" : ObjectId("5acb40d27d63b61cb002bafe"),
    "title" : "WingsOfFire",
    "pub-date" : ISODate("2013-10-02T00:00:00.000Z"),
    "rel-date" : ISODate("2013-11-02T00:00:00.000Z")
}

{
    "_id" : ObjectId("5acb662756539a6734e64e4a"),
    "title" : "WingsOfSmoke",
    "pub-date" : ISODate("2013-11-02T00:00:00.000Z"),
    "rel-date" : ISODate("2013-10-02T00:00:00.000Z")
}

.. the above Java code will print ...

{ "_id" : { "$oid" : "5acb662756539a6734e64e4a" }, "title" : "WingsOfSmoke", "pub-date" : { "$date" : 1383350400000 }, "rel-date" : { "$date" : 1380672000000 } }

... because this document's pub-date (2013-11-02T00:00:00.000Z) is after its rel-date (2013-10-02T00:00:00.000Z).

Note: the $where operator is functionally equivalent but use of that operator comes with some limitations:

$where evaluates JavaScript and cannot take advantage of indexes. Therefore, query performance improves when you express your query using the standard MongoDB operators (e.g., $gt, $in).

In general, you should use $where only when you can’t express your query using another operator. If you must use $where, try to include at least one other standard query operator to filter the result set. Using $where alone requires a collection scan.