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Type:
Bug
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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: 2.5.4
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Component/s: Querying
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Environment:db.serverBuildInfo()
"version" : "2.5.5-pre-",
"gitVersion" : "04221630900335fc6ee0d9922edae9d29f02d66d",
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ALL
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None
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3
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None
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None
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None
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None
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Testing query plans for $elemMatch queries. (Want to validate that adhoc queries supported by the array of
{k: key, v: value}subdocuments still performs.
Generation of test data:
for (i=1; i<100000; i++) {
searchTerms = [];
for (j=1; j<=100 ; j++) {
val = (i+j) % 10
searchTerms[j-1] = {k: j, v: val}
}
db.searchTest.insert({"payload": "document " + i, "searchTerms": searchTerms});
}
db.searchTest.ensureIndex({"searchTerms.k": 1, "searchTerms.v": 1});
2.4.6 explain output:
> db.searchTest.find({searchTerms: {$elemMatch: {k:1, v: 7}}}).explain()
{
"cursor" : "BtreeCursor searchTerms.k_1_searchTerms.v_1",
"isMultiKey" : true,
"n" : 10000,
"nscannedObjects" : 10000,
"nscanned" : 10000,
"nscannedObjectsAllPlans" : 10000,
"nscannedAllPlans" : 10000,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 50,
"indexBounds" : {
"searchTerms.k" : [
[
1,
1
]
],
"searchTerms.v" : [
[
7,
7
]
]
},
"server" : "xxx:27018"
}
2.5.5-pre explain output
> db.searchTest.find({searchTerms: {$elemMatch: {k:1, v: 7}}}).explain()
{
"cursor" : "BasicCursor",
"n" : 10000,
"nscannedObjects" : 99999,
"nscanned" : 99999,
"nscannedObjectsAllPlans" : 100099,
"nscannedAllPlans" : 100099,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 781,
"nChunkSkips" : 0,
"millis" : 1566,
"server" : "xxx:27017"
}
Original index creation and explain testing was done with index intersection enabled, but I have since restarted mongod without index intersection enabled and 2.5.5-pre still fails to use the index.