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Type:
Bug
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Resolution: Won't Fix
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Priority:
Major - P3
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None
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Affects Version/s: 2.0.5, 2.0.6
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Component/s: Index Maintenance, Querying
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Environment:Windows, Linux
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ALL
I noticed very strange behavior IMO when range queries used with compound index where one of indexed fields is array.
Example, I have collection of documents with HierarchyLevel as integer and Parents as array of strings, and other fieds. I make simple query:
{"HierarchyLevel" : {"$gte" : 1, "$lte" : 2}}
When I use simple key index or compound with simple type fields query optimizer runs as expected:
{
"cursor" : "BtreeCursor HierarchyLevel_1",
"nscanned" : 153,
"nscannedObjects" : 153,
"n" : 153,
"millis" : 1,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
"HierarchyLevel" : [
[
1,
2
]
]
}
}
{
"cursor" : "BtreeCursor HierarchyLevel_1_Path_1",
"nscanned" : 153,
"nscannedObjects" : 153,
"n" : 153,
"millis" : 1,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : false,
"indexOnly" : false,
"indexBounds" : {
"HierarchyLevel" : [
[
1,
2
]
],
"Path" : [
[
{
"$minElement" : 1
},
{
"$maxElement" : 1
}
]
]
}
}
But when I use compound index with array field, $lte condition is simply ignored, and all index entries from lower bound is scanned
{
"cursor" : "BtreeCursor HierarchyLevel_1_Parents_1",
"nscanned" : 283630,
"nscannedObjects" : 283630,
"n" : 153,
"millis" : 836,
"nYields" : 0,
"nChunkSkips" : 0,
"isMultiKey" : true,
"indexOnly" : false,
"indexBounds" : {
"HierarchyLevel" : [
[
1,
1.7976931348623157e+308
]
],
"Parents" : [
[
{
"$minElement" : 1
},
{
"$maxElement" : 1
}
]
]
}
}
In this case count of scanned objects is bigger that count of actual documents, and query took lot of time.
- duplicates
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SERVER-4180 Allow multiple constraints (on same field) within a $elemMatch clause to be used with a multikey index
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- Closed
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- is duplicated by
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- Closed
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- is related to
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- Closed
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- related to
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- Closed
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