Question

I am trying to perform a query which is composed of two $or‘s:

|--------------------
| Date1  |  Date2   |
|--------------------
| NULL   |  NULL    | *
| NULL   |  TODAY   | *
| NULL   |  TOMRW   | 
| TODAY  |  TODAY   | *
| TODAY  |  NULL    | *
| TOMRW  |  NULL    | 
|--------------------

(I’ve marked the rows that would match with an asterisk)

(Date1 == null || Date1 <= today) && (Date2 == null || Date2 <= today)

I am not sure how to express this query in MongoDB.

It can be broken down into two individual queries that do exactly what they should:

{
    "$or": [{
        "Date1": {
            "$exists": false
        }
    },
    {
        "Date1": {
            "$exists": true,
            "$lte": new Date("2012-01-07T04:45:52.057Z")
        }
    }]
}

and

{
    "$or": [{
        "Date2": {
            "$exists": false
        }
    },
    {
        "Date2": {
            "$exists": true,
            "$lte": new Date("2012-01-07T04:45:52.057Z")
        }
    }]
}

Both of these select the correct set of documents – I just dont know how to execute them as a single query.

My initial thought was to do a query like this:

{
    $and: [orQuery1, orQuery2]
}

Using an $and query returns 0 results. It was explained why here in this thread: $and query returns no result

Also in that thread, a suggestion was made to do a query like this:

{
    Key: {valToMatch1: 1, valToMatch2: 2}
}

But I dont think an $or can be executed this way.

So, the question is: How do I construct my query such that I can combine the two $or’s into a single query?

(Its getting very late so I hope this question makes sense.)

Answer 1

use test
db.test.insert({a:1})
db.test.insert({a:2, Date2:new Date("01/07/2012")})
db.test.insert({a:3, Date2:new Date("01/08/2012")})
db.test.insert({a:4, Date1:new Date("01/07/2012"), Date2:new Date("01/07/2012")})
db.test.insert({a:5, Date1:new Date("01/07/2012")})
db.test.insert({a:6, Date1:new Date("01/08/2012")})

first subquery
db.test.distinct(‘a’, {…});

[1, 2, 3]

second subquery
db.test.distinct(‘a’, {…});

[ 1, 5, 6 ]

(Date1 == null || Date1 <= today) && (Date2 == null || Date2 <= today)

unwind

Date1 == null && Date2 == null ||
Date1 == null && Date2 <= today ||
Date1 <= today && Date2 == null ||
Date1 <= today && Date2 <= today ||

query

db.test.find(
{
  $or : 
  [
    {$and: [
        {"Date1": {"$exists": false}},
        {"Date2": {"$exists": false}}
      ]},
    {$and: [
        {"Date1": {"$exists": false}},
        {"Date2": {
            "$exists": true,
            "$lte": new Date("2012-01-07T04:45:52.057Z")}
        }
      ]},
    {$and: [
        {"Date2": {"$exists": false}},
        {"Date1": {
            "$exists": true,
            "$lte": new Date("2012-01-07T04:45:52.057Z")}
        }
      ]},
    {$and: [
        {"Date2": {
            "$exists": true,
            "$lte": new Date("2012-01-07T04:45:52.057Z")}
        },
        {"Date1": {
            "$exists": true,
            "$lte": new Date("2012-01-07T04:45:52.057Z")}
        }
      ]}
  ]
})
>[ 1 ]

this should work too (assume that ‘not exist’ and ‘null’ is the same)

db.test.find(
{
  $and : 
  [
    {$or: [
        {"Date1": null},
        {"Date1": { "$lte": new Date("2012-01-07T04:45:52.057Z")} }
      ]},
    {$or: [
        {"Date2": null},
        {"Date2": { "$lte": new Date("2012-01-07T04:45:52.057Z")} }
      ]}
  ]
}
)