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Type:
Question
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Resolution: Done
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Priority:
Major - P3
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None
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Affects Version/s: 2.6.3
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Component/s: Geo
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None
I'm managing a 10k x 10k planar grid, in which I wish to use a 2d index for distance calculations/queries. For that, each entry in this grid is a document with a 'loc' field with its coordinates. Such coordinates, therefore, are integers between 0 and 9999 inclusive. The index creation needs then to specify a 'min' and a 'max'.
In v2.4, queries on exact coordinates work as expected, returning almost immediately, with nscanned:1:
db.loc_test.find({loc:[23,24]}).explain()
{
"cursor" : "GeoBrowse-circle",
"isMultiKey" : false,
"n" : 1,
"nscannedObjects" : 1,
"nscanned" : 1,
"nscannedObjectsAllPlans" : 1,
"nscannedAllPlans" : 1,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
...
After upgrading to v2.6.3, the same query performs a full scan:
db.loc_test.find({loc:[23,24]}).explain()
{
"cursor" : "BasicCursor",
"isMultiKey" : false,
"n" : 1,
"nscannedObjects" : 6250000,
"nscanned" : 6250000,
"nscannedObjectsAllPlans" : 6250000,
"nscannedAllPlans" : 6250000,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 49010,
"nChunkSkips" : 0,
"millis" : 32279,
I am not sure 2d indexes on such ranges are actually allowed...