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  1. Core Server
  2. SERVER-12175

Version 2dsphere indexes

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    Details

    • Type: Bug
    • Status: Closed
    • Priority: Major - P3
    • Resolution: Fixed
    • Affects Version/s: 2.5.4
    • Fix Version/s: 2.4.10, 2.6.0-rc0
    • Component/s: Geo
    • Labels:
    • Operating System:
      ALL

      Description

      Issue Status as of March 28, 2014

      ISSUE SUMMARY
      This issue introduces versions for 2dsphere indexes. This was necessary as new features were added to 2dsphere indexes in MongoDB version 2.6, for example support for new GeoJSON objects like MultiPoint and GeometryCollection. A downgrade from version 2.6 to 2.4 would otherwise not be able to detect the new index implementation and could potentially corrupt the index.

      USER IMPACT
      Users are affected if they use a 2dsphere index with any of the new GeoJSON documents in version 2.6 (which are MultiPoint, MultiLineString, MultiPolygon and GeometryCollection) and then downgrade to version 2.4. This can cause index corruption and return wrong query results.

      SOLUTION
      Introduce versions for 2dsphere indexes, include checks for version 1 (old format) 2dsphere indexes if it indexes a geometry that was introduced in later versions (e.g. MultiPoint).

      WORKAROUNDS
      Users who want to downgrade mongod from version 2.6 to 2.4 should drop the 2dsphere index before the downgrade.

      AFFECTED VERSIONS
      All versions from 2.4.0 to 2.4.9 are affected.

      PATCHES
      The fix is included in the production release 2.4.10.

      Original Description

      Add new index option "2dsphereIndexVersion" to 2dsphere indexes.

      Version 1 can't index MultiPoint, MultiLineString, MultiPolygon, or GeometryCollection (index build will fail if docs present, and inserting doc will fail if index present). Version 2 can index these.

      2.4 builds version 1 indexes, and cannot build/use version 2 indexes. Drop version 2 indexes before downgrading 2.6=>2.4.

      2.6 builds version 2 indexes by default, and is able to build/use version 1 too.

      Original description:

      Documents with 2.6-only GeoJSON types can be missing _id index entries after 2.4 downgrade

      The GeoJSON types MultiPoint, MultiLineString, MultiPolygon, and GeometryCollection were introduced in 2.5. As such, version 2.4 of the server cannot unindex these documents from 2dsphere indexes. Attempting to delete such a document after downgrading 2.6=>2.4 will cause the document to be only half-removed: it will be successfully removed from the lower-numbered indexes (like the _id index), but will remain in the 2dsphere and higher-numbered indexes, and will remain in the collection.

      Having a collection with missing index entries is problematic, especially for the _id index. Running mongodump against the mongod will generate a dump that is missing these documents (since a snapshot query is issued). If the mongod later becomes a secondary, it will fail to apply updates from the oplog against these documents (since the oplog writers locate such documents with the _id index).

      Reproduce with the following, in 2.5.4:

      > db.foo.ensureIndex({loc:"2dsphere"})
      > db.foo.insert({loc:{type:"MultiPoint",coordinates:[[-73.9580, 40.8003]]}})
      Insert WriteResult({ "ok" : 1, "nDocsModified" : 0, "n" : 1 })

      Followed by the following, after downgrading to 2.4.8:

      > db.foo.validate().keysPerIndex
      { "test.foo.$_id_" : 1, "test.foo.$loc_2dsphere" : 1 }
      > db.foo.remove(); db.getLastError()
      Can't extract geo keys from object, malformed geometry?:{ type: "MultiPoint", coordinates: [ [ -73.958, 40.8003 ] ] }
      > db.foo.validate().keysPerIndex
      { "test.foo.$_id_" : 0, "test.foo.$loc_2dsphere" : 1 }
      > db.foo.find().hint({$natural:1}).itcount()
      1
      > db.foo.find().hint({_id:1}).itcount()
      0

      At the default logging severity, no log output is generated for this error.

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                  Updated:
                  Resolved: