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Type:
Bug
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Resolution: Duplicate
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Priority:
Major - P3
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None
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Affects Version/s: 2.6.0-rc0
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Component/s: Querying
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Labels:
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ALL
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The following regex query takes roughly 8x longer in v2.6.0-rc0 vs. v2.4.9:
db.QA401.find({ _id: /Big(ww)i/ }).sort({a:1})
The test collection has 920 documents (see attached) with the following indices:
db.QA401.ensureIndex({a:-1})
db.QA401.ensureIndex({'a.a':-1})
db.QA401.ensureIndex({'a.a.a':-1})
v2.6.0-rc0:
> db.QA401.find({ _id: /Big(ww)i/ }).sort({a:1}).explain();
{
"cursor" : "BtreeCursor _id_",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 0,
"nscanned" : 1,
"nscannedObjectsAllPlans" : 1,
"nscannedAllPlans" : 2,
"scanAndOrder" : true,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 0,
"indexBounds" : {
"_id" : [
[
"",
{
}
],
[
/Big(ww)i/,
/Big(ww)i/
]
]
},
"server" : "zzyzx:27017",
"filterSet" : false
}
v2.4.9:
> db.QA401.find({ _id: /Big(ww)i/ }).sort({a:1}).explain();
{
"cursor" : "BtreeCursor _id_ multi",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 0,
"nscanned" : 1,
"nscannedObjectsAllPlans" : 0,
"nscannedAllPlans" : 3,
"scanAndOrder" : true,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 0,
"indexBounds" : {
"_id" : [
[
"",
{
}
],
[
/Big(ww)i/,
/Big(ww)i/
]
]
},
"server" : "zzyzx:27018"
}
The query times are sub-millisecond; here is the output from QA-401:
{
"_id" : ObjectId("530f6bad7e6c53525919dfb6"),
"deltaRatio" : "8.40",
"deltaUs" : 741,
"v249Avg" : "100.17",
"v249Results" : [
100,
102,
101,
99,
100,
99
],
"rc0Avg" : "841.17",
"rc0Results" : [
870,
882,
839,
817,
815,
824
],
"testId" : "GeneratedTests::GeneratedQuery750[Descending]",
"qry" : "{ query: { _id: //Big(ww)i// }, orderby: { a: 1 } }",
"proj" : "{ NONE: 1 }",
"idx" : "Descending",
"rc0Count" : 0,
"v249Count" : 0,
"countsMatch" : true
}
I'm having a tough time distilling this down to something which can be reproduced in the shell (with measurable results).
- is duplicated by
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- Closed
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- is related to
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SERVER-12287 Query containing $regex operator: performance regression
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- Closed
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