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  1. Core Server
  2. SERVER-6146

aggregation framework should have an $in expression

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    • Fully Compatible
    • Query 13 (04/22/16)

      Syntax

      {$in: [<arbitrary expression>, <arbitrary array expression>]}

      Examples

      db.coll.insert([
  {_id: 0, x: "Bob"}
]);
> db.coll.aggregate([{
  $project: {
    hasBobOrRob: {$in: ["$x", ["Bob", "Rob"]]}
  }
}]);
{_id: 0, hasBobOrRob: true}

// Example 2
> db.coll.insert([
  {_id: 0, x: "aaa"},
  {_id: 1, x: /^a/}
]);
> db.coll.aggregate([{
  $project: {
    matches: {$in: ["$x", [/^a/]]}
  }
}])
{_id: 0, matches: false}
{_id: 1, matches: true}
// Note the intentional inconsistency.
> db.foo.find({x: {$in: [/^a/]}})
{_id: 0, x: "aaa"}
{_id: 1, x: /^a/}

      Notes

      • Should result in the same values as a $in in a MatchExpression (except with regexes).
      • Should not do regex matching if the values in the array are regexes.
      • This is different from what the query system does, a query predicate of {x: {$in: [/^a/]} will find strings which start with "a". This is arguably a bug in query, and will not be duplicated here.

      Errors

      • If the second expression is not an array.
      • If there are not two arguments passed to the expression.

      Old Description
      Currently expressions like $eq, $ne, $gt, etc are supported but there is no $in available to test set membership.

            Assignee:
            benjamin.murphy Benjamin Murphy
            Reporter:
            aaron Aaron Staple
            Votes:
            18 Vote for this issue
            Watchers:
            18 Start watching this issue

              Created:
              Updated:
              Resolved: