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https://issues.apache.org/jira/browse/OAK-2621?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Michael Marth updated OAK-2621:
-------------------------------
Fix Version/s: (was: 1.3.5)
1.3.7
> Too many reads for child nodes
> ------------------------------
>
> Key: OAK-2621
> URL: https://issues.apache.org/jira/browse/OAK-2621
> Project: Jackrabbit Oak
> Issue Type: Improvement
> Components: mongomk
> Affects Versions: 1.0
> Reporter: Marcel Reutegger
> Labels: performance
> Fix For: 1.3.7
>
>
> The DocumentNodeStore issues a lot of reads when sibling nodes are deleted,
> which are also index with a property index.
> The following calls will become a hotspot:
> {noformat}
> at
> org.apache.jackrabbit.oak.plugins.document.mongo.MongoDocumentStore.query(MongoDocumentStore.java:406)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.readChildDocs(DocumentNodeStore.java:846)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.readChildren(DocumentNodeStore.java:788)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeStore.getChildren(DocumentNodeStore.java:753)
> at
> org.apache.jackrabbit.oak.plugins.document.DocumentNodeState.getChildNodeCount(DocumentNodeState.java:194)
> at
> org.apache.jackrabbit.oak.plugins.memory.ModifiedNodeState.getChildNodeCount(ModifiedNodeState.java:198)
> at
> org.apache.jackrabbit.oak.plugins.memory.MutableNodeState.getChildNodeCount(MutableNodeState.java:265)
> at
> org.apache.jackrabbit.oak.plugins.memory.MemoryNodeBuilder.getChildNodeCount(MemoryNodeBuilder.java:293)
> at
> org.apache.jackrabbit.oak.plugins.index.property.strategy.ContentMirrorStoreStrategy.prune(ContentMirrorStoreStrategy.java:456)
> {noformat}
> I think the code triggering this issue is in
> {{ModifiedNodeState.getChildNodeCount()}}. It keeps track of already deleted
> children and requests {{max += deleted}}. The actual {{max}} is always 1 as
> requested from {{ContentMirrorStoreStrategy.prune()}}, but as more nodes get
> deleted, the higher {{max}} gets passed to
> {{DocumentNodeState.getChildNodeCount()}}. The DocumentNodeStore then checks
> if it has the children in the cache, only to find out the cache entry has too
> few entries and it needs to fetch one more.
> It would be best to have a minimum number of child nodes to fetch from
> MongoDB in this case. E.g. when NodeState.getChildNodeEntries() is called,
> the DocumentNodeState fetches 100 children.
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