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https://issues.apache.org/jira/browse/JENA-1988?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17228822#comment-17228822
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Andy Seaborne commented on JENA-1988:
-------------------------------------
The cache is {{NodeTableCache}}
A database will have a stack of {{NodeTable}} implementations
{{NodeTableInline}} > {{NodeTableCache}} > {{NodeTableNative}} (and
{{NodeTableTRDF}} for TDB2).
See {{DatasetBuilderStd.buildNodeTable}} (TDB1) and
{{TDB2StorageBuilder.buildNodeTable}} (TDB2).
Also - while the {{Index}} (a map) is in fact a {{RangeIndex}} (sorted map), in
TDB2 this is tied up with the transaction mechanism.
Do you have figures for the cost of the node table to you?
> Separating B+ tree into different Node representations.
> -------------------------------------------------------
>
> Key: JENA-1988
> URL: https://issues.apache.org/jira/browse/JENA-1988
> Project: Apache Jena
> Issue Type: Question
> Components: TDB
> Affects Versions: Jena 3.16.0
> Reporter: Martin Pekár
> Priority: Major
> Labels: features, newbie, performance, test
> Fix For: Jena 3.16.0
>
> Attachments: NodeTableNative.java
>
>
> In a project to optimize the indexing, I am trying to have 4 indexes, one for
> each Node type (variable, literal, URI and blank). To implement this, I added
> 4 copies of the _nodeHashToId_ Index instance in the _NodeTableNative_ class.
> Then, for every operation on the _nodeHashToId_, for example using
> _containsNode()_ in the NodeTableNative class, I first check the type of Node
> given as parameter and then check for existence in the appropriate
> _nodeHashToId_ copy.
> Now, for some reason I get a NullPointerException when running the tests.
> Many of these exceptions appear in the _BufferChannelFile_ class in the
> _size()_ method because the call to _file.channel()_ return null.
> My question is then, is _NodeTableNative___ even the right place to implement
> this optimization, and second, if it is the right place to implement, can you
> help me understand why this exception is thrown?
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