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  1. Core Server
  2. SERVER-27089

Extend the update subsystem to support more expressive updates to array fields

    • Type: Icon: New Feature New Feature
    • Resolution: Done
    • Priority: Icon: Major - P3 Major - P3
    • 3.5.12
    • Affects Version/s: None
    • Component/s: Querying, Write Ops
    • None
    • Fully Compatible
    • Query 2017-08-21

      Issue Status as of Aug 11, 2017

      MongoDB 3.5.12 extends all update modifiers to apply to all array elements or all array elements that match a predicate, specified in a new update option arrayFilters. This syntax also supports nested array elements.

      This new feature is available starting with the MongoDB 3.5.12 development version, and included in the MongoDB 3.6 production version.


      Update all documents in array

      db.coll.update({}, {$set: {“a.$[].b”: 2}})
      Input: {a: [{b: 0}, {b: 1}]}
      Output: {a: [{b: 2}, {b: 2}]}

      Update all matching documents in array

      db.coll.update({}, {$set: {“a.$[i].b”: 2}}, {arrayFilters: [{“i.b”: 0}]})
      Input: {a: [{b: 0}, {b: 1}]}
      Output: {a: [{b: 2}, {b: 1}]}

      Update all matching scalars in array

      db.coll.update({}, {$set: {“a.$[i]”: 2}}, {arrayFilters: [{i: 0}]})
      Input: {a: [0, 1]}
      Output: {a: [2, 1]}

      Update all matching documents in nested array

      db.coll.update({}, {$set: {“a.$[i].c.$[j].d”: 2}}, {arrayFilters: [{“i.b”: 0}, {“j.d”: 0}]})
      Input: {a: [{b: 0, c: [{d: 0}, {d: 1}]}, {b: 1, c: [{d: 0}, {d: 1}]}]}
      Output: {a: [{b: 0, c: [{d: 2}, {d: 1}]}, {b: 1, c: [{d: 0}, {d: 1}]}]}

      Update all scalars in array matching a logical predicate

      db.coll.update({}, {$set: {“a.$[i]”: 2}}, {arrayFilters: [{$or: [{i: 0}, {i: 3}]}]})
      Input: {a: [0, 1, 3]}
      Output: {a: [2, 1, 2]}

      Each array filter must be a predicate over a document with a single field name. Each array filter must be used in the update expression, and each array filter identifier $[<id>] must have a corresponding array filter. <id> must begin with a lowercase letter and not contain any special characters. There must not be two array filters with the same field name.

      The implementation of this feature involved a rewrite of the update system. Users can find all the related tickets here. The design document is attached.

      Original description

            tess.avitabile@mongodb.com Tess Avitabile (Inactive)
            david.storch@mongodb.com David Storch
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