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  1. Core Server
  2. SERVER-12281

When choosing multikey index bounds, never choose a superset if a subset is available

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Details

    • Improvement
    • Status: Backlog
    • Major - P3
    • Resolution: Unresolved
    • 2.5.4
    • None
    • Querying
    • Query Optimization

    Description

      For queries with multiple predicates over a multikey field, you can't intersect the index bounds. Suppose there is a multikey index on field 'a'. The following query

      db.t.find({a: {$lte: 0, $gte: 1}});

      would have empty index bounds if 'a' were not a multikey field. Since it is multikey, however, we either use bounds

      [-Infinity, 0]

      or

      [1, Infinity]

      Which bounds to use is chosen arbitrarily. As an optimization, we could make sure that we always choose the smallest interval over which to perform the index scan. For instance, for the query

      db.t.find({a: {$gt: 4, $gte: 5}});

      we would choose

      [5, Infinity]

      rather than

      (4, Infinity]

      because the former is a subset of the latter.

      Attachments

        Issue Links

          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. SERVER-14519 $and $ne performance degradation in 2.6

          • Major - P3 - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. SERVER-15214 $nin operator avoid query execution over a specific index

          • Major - P3 - Major loss of function.
          • Closed

          Bug - A problem which impairs or prevents the functions of the product. SERVER-15658 Query with $in and $nin doesn't use index correctly

          • Minor - P4 - Minor loss of function, or other problem where easy workaround is present.
          • Closed
          is related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-13273 multiple predicates for $all and multiKey index is order dependent

          • Major - P3 - Major loss of function.
          • Closed

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-16042 Optimise $all/$and to select smallest subset as initial index bounds

          • Major - P3 - Major loss of function.
          • Closed
          related to

          Bug - A problem which impairs or prevents the functions of the product. SERVER-12470 document and audit multikey bounds behavior

          • Major - P3 - Major loss of function.
          • Closed

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-18364 Ensure non-negation predicates get chosen over negation predicates for multikey index bounds construction

          • Major - P3 - Major loss of function.
          • Closed

          Activity

            People

              backlog-query-optimization Backlog - Query Optimization
              david.storch@mongodb.com David Storch
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              11 Vote for this issue
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              21 Start watching this issue

              Dates

                Created:
                Updated: