Details
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Question
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Resolution: Duplicate
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Major - P3
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None
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2.4.6
Description
I have a collection called search2 with about 20000 documents like this:
{
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"loc": {
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"type": "Polygon",
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"coordinates": [
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[
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[
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43.78526674007639,
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11.14739998758569
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],
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[
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43.78526674007639,
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11.183372851822439
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],
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[
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43.79443488391605,
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11.183372851822439
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],
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[
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43.79443488391605,
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11.264311796355125
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],
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[
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43.812771171595415,
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11.264311796355125
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],
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[
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43.83110745927479,
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11.264311796355125
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],
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[
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43.83110745927479,
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11.273305012414314
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],
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[
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43.849443746954144,
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11.273305012414314
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],
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[
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43.858611890793824,
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11.273305012414314
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],
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[
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43.858611890793824,
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11.264311796355125
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],
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[
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43.8769481784732,
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11.264311796355125
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],
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[
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43.8769481784732,
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11.246325364236752
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],
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[
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43.88611632231286,
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11.246325364236752
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],
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[
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43.88611632231286,
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11.237332148177565
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],
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[
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43.895284466152546,
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11.237332148177565
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],
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[
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43.895284466152546,
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11.228338932118376
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],
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[
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43.904452609992234,
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11.228338932118376
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],
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[
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43.904452609992234,
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11.165386419704065
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],
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[
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43.895284466152546,
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11.165386419704065
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],
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[
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43.895284466152546,
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11.156393203644878
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],
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[
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43.88611632231286,
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11.156393203644878
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],
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[
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43.8769481784732,
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11.156393203644878
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],
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[
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43.858611890793824,
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11.156393203644878
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],
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[
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43.849443746954144,
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11.156393203644878
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],
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[
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43.849443746954144,
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11.165386419704065
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],
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[
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43.83110745927479,
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11.165386419704065
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],
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[
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43.83110745927479,
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11.156393203644878
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],
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[
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43.812771171595415,
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11.156393203644878
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],
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[
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43.812771171595415,
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11.14739998758569
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],
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[
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43.79443488391605,
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11.14739998758569
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],
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[
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43.78526674007639,
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11.14739998758569
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]
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]
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]
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},
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"docId": 1,
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"docVote": 0,
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"title": "title-1",
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"_id": {
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"$oid": "5248725d2dd5622510000001"
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}
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}
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I define an index with this command:
db.search2.ensureIndex({"docVote": 1,"loc":"2dsphere"});
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On the collection there are only this index and the default index on "_id" field.
When i execute the following query i expect "nscannedObjects" to be = 10 :
db.search2.find({
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loc: {
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$geoIntersects: {
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$geometry: {
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type: "Polygon",
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coordinates: [
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[
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[43.7269795, 11.1540365],
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[43.8329368, 11.1540365],
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[43.8329368, 11.3310908],
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[43.7269795, 11.3310908],
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[43.7269795, 11.1540365]
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]
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]
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}
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}
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}
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}, {
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"docVote": 1,
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_id: 0
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}).sort({
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"docVote": 1
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}).limit(10).hint({
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"docVote": 1,
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"loc": "2dsphere"
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}).explain()
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But this is the result:
{
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"cursor" : "S2Cursor",
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"isMultiKey" : true,
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"n" : 10,
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"nscannedObjects" : 44283,
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"nscanned" : 648117,
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"nscannedObjectsAllPlans" : 44283,
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"nscannedAllPlans" : 648117,
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"scanAndOrder" : true,
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"indexOnly" : false,
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"nYields" : 13,
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"nChunkSkips" : 0,
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"millis" : 12632,
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"indexBounds" : {
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|
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},
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"nscanned" : 648117,
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"matchTested" : NumberLong(46642),
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"geoTested" : NumberLong(46642),
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"cellsInCover" : NumberLong(8),
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"server" : "*********"
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}
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If i remove sort from the query i obtain this:
{
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"cursor" : "S2Cursor",
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"isMultiKey" : true,
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"n" : 10,
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"nscannedObjects" : 10,
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"nscanned" : 25,
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"nscannedObjectsAllPlans" : 10,
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"nscannedAllPlans" : 25,
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"scanAndOrder" : false,
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"indexOnly" : false,
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"nYields" : 0,
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"nChunkSkips" : 0,
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"millis" : 3,
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"indexBounds" : {
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|
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},
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"nscanned" : 25,
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"matchTested" : NumberLong(10),
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"geoTested" : NumberLong(10),
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"cellsInCover" : NumberLong(8),
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"server" : "******"
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}
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So, why index is not used to sort results? From this documentation: http://docs.mongodb.org/manual/applications/geospatial-indexes/ http://docs.mongodb.org/manual/tutorial/sort-results-with-indexes/ I understand that MongoDb support "A compound index with scalar index fields (i.e. ascending or descending) as a prefix or suffix of the 2dsphere index field" and that "If the sort document is a subset of a compound index and starts from the beginning of the index, MongoDB can use the index to both retrieve and sort the query results."
What am I missing?
Thanks in advance
Attachments
Issue Links
- duplicates
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SERVER-10801 Allow compound geo indexes to be able to provide sort
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- Backlog
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