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https://issues.apache.org/jira/browse/OAK-2007?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14079323#comment-14079323
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Przemo Pakulski edited comment on OAK-2007 at 7/30/14 2:48 PM:
---------------------------------------------------------------
On my instance (50k chunks) query with _id_ hint takes up to 8 minutes
> db.blobs.find({lastMod : {$lte :1306726400279}},
> {_id:1}).hint({_id:1}).explain()
{
"cursor" : "BtreeCursor _id_",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 50204,
"nscanned" : 50204,
"nscannedObjectsAllPlans" : 50204,
"nscannedAllPlans" : 50204,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 15280,
"nChunkSkips" : 0,
"millis" : 462653,
"indexBounds" : {
"_id" : [
[
{
"$minElement" : 1
},
{
"$maxElement" : 1
}
]
]
},
"server" : "cqzg-aem6-stable:27017",
"filterSet" : false
}
The same query without any hints and index on _lastMod_ created is instant
> db.blobs.find({lastMod : {$lte :1306726400279}}, {_id:1}).explain()
{
"cursor" : "BtreeCursor lastMod_1",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 0,
"nscanned" : 0,
"nscannedObjectsAllPlans" : 0,
"nscannedAllPlans" : 0,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 0,
"nChunkSkips" : 0,
"millis" : 0,
"indexBounds" : {
"lastMod" : [
[
-Infinity,
1306726400279
]
]
},
"server" : "cqzg-aem6-stable:27017",
"filterSet" : false
}
was (Author: ppakulski):
On my instance (50k chunks) query with _id_ hint takes up to 8 minutes
> db.blobs.find({lastMod : {$lte :1306726400279}},
> {_id:1}).hint({_id:1}).explain()
{
"cursor" : "BtreeCursor _id_",
"isMultiKey" : false,
"n" : 0,
"nscannedObjects" : 50204,
"nscanned" : 50204,
"nscannedObjectsAllPlans" : 50204,
"nscannedAllPlans" : 50204,
"scanAndOrder" : false,
"indexOnly" : false,
"nYields" : 15280,
"nChunkSkips" : 0,
"millis" : 462653,
"indexBounds" : {
"_id" : [
[
{
"$minElement" : 1
},
{
"$maxElement" : 1
}
]
]
},
"server" : "cqzg-aem6-stable:27017",
"filterSet" : false
}
> MongoBlobStore improvements
> ---------------------------
>
> Key: OAK-2007
> URL: https://issues.apache.org/jira/browse/OAK-2007
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: blob, mongomk
> Affects Versions: 1.0.2
> Reporter: Przemo Pakulski
> Attachments: OAK-2007.patch
>
>
> To collect all chunk identifiers (getAllChunkIds) hint is used to force "_id"
> index usage.
> This index doesn't help because query is using "lastMod" field. It also
> doesn't allow to leverage custom indexes if created. In result queries are
> pretty slow.
> Additionally consider to create index on "lastMod" field to speed-up all
> queries using this criteria.
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