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  1. Core Server
  2. SERVER-12869

Index null values and missing values differently

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Details

    • Improvement
    • Status: Backlog
    • Major - P3
    • Resolution: Unresolved
    • 2.6.0-rc0
    • None
    • Index Maintenance, Querying
    • None
    • Query Optimization

    Description

      A document with a missing value are stored as if they were
      explicitly given the value 'null'. Given: 

      X = { b : 1 }                                                                                                                                                                                  
      Y = { a : null, b : 1 }

      X and Y look identical from within a standard index on

      { a : 1 }

      However a sparse index on

      { a : 1 }

      will treat X and Y differently,
      storing Y and not storing X.

      We can safely use an index on $exists queries in the following cases:
      {a:{ $exists:true }} - normal index helps, but we must still fetch
      {a:{ $exists:true }} - sparse index is exact
      {a:{ $exists:false }} - normal index requires a fetch
      {a:{ $exists:false }} - never

      Attachments

        Issue Links

          is depended on by

          Bug - A problem which impairs or prevents the functions of the product. SERVER-13298 distinct doesn't use index to distinct multikey dotted fields

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

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-18861 Queries matching null value should be fully covered by index

          • Major - P3 - Major loss of function.
          • Backlog
          is duplicated by

          Bug - A problem which impairs or prevents the functions of the product. SERVER-52845 $exists works slowly

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-67378 Index null values and missing values differently

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

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-17376 Allow $exists to efficiently use indexes

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-14832 Distinct command result set may include or exclude null/undefined depending on presence of index

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-6293 Index only query fills in missing values with null

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-12557 $exists could use index

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-55065 Null queries should be covered by index where possible with current index format

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

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-18861 Queries matching null value should be fully covered by index

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

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-12262 Use full index scan as proxy for collection scan in order to make certain queries covered

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-23229 Projection incorrectly returns null value instead of missing field to user if projection is covered

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

          Bug - A problem which impairs or prevents the functions of the product. SERVER-67378 Index null values and missing values differently

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

          Improvement - An improvement or enhancement to an existing feature or task. SERVER-54811 Bad query plans for $exists:true queries

          • Major - P3 - Major loss of function.
          • Backlog
          mentioned in

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              backlog-query-optimization Backlog - Query Optimization
              samantha.ritter@mongodb.com Samantha Ritter (Inactive)
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              Dates

                Created:
                Updated: