Details
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Bug
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Status: Closed
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Major - P3
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Resolution: Works as Designed
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2.5.4
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None
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db.serverBuildInfo()
"version" : "2.5.5-pre-",
"gitVersion" : "04221630900335fc6ee0d9922edae9d29f02d66d",
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ALL
Description
Testing query plans for $elemMatch queries. (Want to validate that adhoc queries supported by the array of
{k: key, v: value}subdocuments still performs.
Generation of test data:
for (i=1; i<100000; i++) {
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searchTerms = [];
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for (j=1; j<=100 ; j++) {
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val = (i+j) % 10
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searchTerms[j-1] = {k: j, v: val}
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}
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db.searchTest.insert({"payload": "document " + i, "searchTerms": searchTerms});
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}
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db.searchTest.ensureIndex({"searchTerms.k": 1, "searchTerms.v": 1});
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2.4.6 explain output:
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> db.searchTest.find({searchTerms: {$elemMatch: {k:1, v: 7}}}).explain()
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{
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"cursor" : "BtreeCursor searchTerms.k_1_searchTerms.v_1",
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"isMultiKey" : true,
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"n" : 10000,
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"nscannedObjects" : 10000,
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"nscanned" : 10000,
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"nscannedObjectsAllPlans" : 10000,
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"nscannedAllPlans" : 10000,
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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" : 50,
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"indexBounds" : {
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"searchTerms.k" : [
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[
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1,
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1
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]
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],
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"searchTerms.v" : [
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[
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7,
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7
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]
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]
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},
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"server" : "xxx:27018"
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}
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2.5.5-pre explain output
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> db.searchTest.find({searchTerms: {$elemMatch: {k:1, v: 7}}}).explain()
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{
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"cursor" : "BasicCursor",
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"n" : 10000,
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"nscannedObjects" : 99999,
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"nscanned" : 99999,
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"nscannedObjectsAllPlans" : 100099,
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"nscannedAllPlans" : 100099,
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"scanAndOrder" : false,
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"indexOnly" : false,
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"nYields" : 781,
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"nChunkSkips" : 0,
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"millis" : 1566,
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"server" : "xxx:27017"
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}
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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.