datafabricrus / scylla-rdf Goto Github PK

An RDF store based on ScyllaDB and Eclipse RDF4J

License: MIT License

Kotlin 12.26% XSLT 0.44% Java 87.27% Dockerfile 0.02%

scylla-rdf's Introduction

Scylla RDF

An RDF store (aka Triplestore) built using Eclipse RDF4J and ScyllaDB. Full-text search is supported with Elasticsearch.

Warning: It's still in an early stage of development, so if you have any trouble or question, please, create an issue.

Deployment

For testing purposes deploy ScyllaDB, Elasticsearch and Scylla-RDF locally using docker-compose-dev.yml:

$ docker-compose -f docker-compose-dev.yml up -d

For production, you need to deploy ScyllaDB and Elasticsearch separately. And use docker-compose-prod.yml to deploy Scylla-RDF. Scylla-RDF were tested with:

ScyllaDB 3.0.10
Elasticsearch 6.5.4

In both cases, after the deployment, you need to create a repository via the RDF4J Workbench Console which'll be available on 80th port of the machine where Scylla-RDF was deployed, e.g. http://localhost. The default login/password: admin/scylla-rdf.

Bulk Loading

We use Apache Beam to bulk load RDF data to ScyllaDB. The repository with the source code and instructions: https://github.com/DataFabricRus/scylla-beam-pipelines.

Benchmarks

We benchmark new features, the results available in https://github.com/DataFabricRus/scylla-rdf-benchmark.

Build from sources

$ mvn clean install
$ docker-compose -f docker-compose-dev.yml build

License

MIT License

scylla-rdf's People

Contributors

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aahmadai

scylla-rdf's Issues

Counting cardinality estimations may become negative

The card(c), card(p) and card(p, o) may be below zero, which is wrong. Maybe fixed by using the conditional UPDATE which would check if the counter is not less than the decrement.

Implement clearing repository through the sail connection

com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed

I successfully deployed scylla-rdf to docker then got into RDF4J Workbench and can create repositories. The problem is that I can't do anything else, when I try to access Namespaces, Contexts, and all other tabs I get similar exceptions:

HTTP Status 500 – Internal Server Error
Type Exception Report

Message org.eclipse.rdf4j.repository.RepositoryException: org.eclipse.rdf4j.repository.RepositoryException: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /0.0.4.87:9042 (com.datastax.driver.core.exceptions.TransportException: [/0.0.4.87:9042] Cannot connect))

Description The server encountered an unexpected condition that prevented it from fulfilling the request.

Exception

javax.servlet.ServletException: org.eclipse.rdf4j.repository.RepositoryException: org.eclipse.rdf4j.repository.RepositoryException: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /0.0.4.87:9042 (com.datastax.driver.core.exceptions.TransportException: [/0.0.4.87:9042] Cannot connect))
	org.eclipse.rdf4j.workbench.proxy.WorkbenchServlet.handleRequest(WorkbenchServlet.java:140)
	org.eclipse.rdf4j.workbench.proxy.WorkbenchServlet.service(WorkbenchServlet.java:103)
	org.eclipse.rdf4j.workbench.proxy.WorkbenchGateway.service(WorkbenchGateway.java:114)
	org.eclipse.rdf4j.workbench.base.AbstractServlet.service(AbstractServlet.java:125)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:109)
	org.eclipse.rdf4j.workbench.proxy.CacheFilter.doFilter(CacheFilter.java:61)
	org.eclipse.rdf4j.workbench.proxy.CookieCacheControlFilter.doFilter(CookieCacheControlFilter.java:53)
Root Cause

org.eclipse.rdf4j.repository.RepositoryException: org.eclipse.rdf4j.repository.RepositoryException: com.datastax.driver.core.exceptions.NoHostAvailableException: All host(s) tried for query failed (tried: /0.0.4.87:9042 (com.datastax.driver.core.exceptions.TransportException: [/0.0.4.87:9042] Cannot connect))
	org.eclipse.rdf4j.http.client.SPARQLProtocolSession.execute(SPARQLProtocolSession.java:1019)
	org.eclipse.rdf4j.http.client.SPARQLProtocolSession.executeOK(SPARQLProtocolSession.java:958)
	org.eclipse.rdf4j.http.client.SPARQLProtocolSession.sendTupleQueryViaHttp(SPARQLProtocolSession.java:755)
	org.eclipse.rdf4j.http.client.SPARQLProtocolSession.getTupleQueryResult(SPARQLProtocolSession.java:690)
	org.eclipse.rdf4j.http.client.RDF4JProtocolSession.getNamespaces(RDF4JProtocolSession.java:359)
	org.eclipse.rdf4j.http.client.RDF4JProtocolSession.getNamespaces(RDF4JProtocolSession.java:344)
	org.eclipse.rdf4j.repository.http.HTTPRepositoryConnection.getNamespaces(HTTPRepositoryConnection.java:726)
	org.eclipse.rdf4j.workbench.commands.NamespacesServlet.service(NamespacesServlet.java:49)
	org.eclipse.rdf4j.workbench.base.TransformationServlet.service(TransformationServlet.java:111)
	org.eclipse.rdf4j.workbench.base.TransformationServlet.service(TransformationServlet.java:95)
	org.eclipse.rdf4j.workbench.base.AbstractServlet.service(AbstractServlet.java:125)
	org.eclipse.rdf4j.workbench.proxy.ProxyRepositoryServlet.service(ProxyRepositoryServlet.java:99)
	org.eclipse.rdf4j.workbench.proxy.WorkbenchServlet.service(WorkbenchServlet.java:188)
	org.eclipse.rdf4j.workbench.proxy.WorkbenchServlet.handleRequest(WorkbenchServlet.java:128)
	org.eclipse.rdf4j.workbench.proxy.WorkbenchServlet.service(WorkbenchServlet.java:103)
	org.eclipse.rdf4j.workbench.proxy.WorkbenchGateway.service(WorkbenchGateway.java:114)
	org.eclipse.rdf4j.workbench.base.AbstractServlet.service(AbstractServlet.java:125)
	org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
	org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:109)
	org.eclipse.rdf4j.workbench.proxy.CacheFilter.doFilter(CacheFilter.java:61)
	org.eclipse.rdf4j.workbench.proxy.CookieCacheControlFilter.doFilter(CookieCacheControlFilter.java:53)

Here is what I do to deploy:

Build ScyllaDB Java Driver 3.7.1-scylla branch and RDF4J (rdf4j, rdf4j-storage and rdf4j-tools) develop branch.
Build and deploy scylla-rdf.

mvn clean install
docker-compose -f docker-compose-dev.yml up -d

Access http://localhost and get to RDF4J Workbench. No password is required for some reason.
Create repositories.
Can't access other tabs other than Modify options, but if try to add some data it throws the same exception.

Am I doing something wrong?

This is what I see in the summary of the repository:

And all repositories:

I get the same result on two different PCs running Windows 10 Pro.

Edit: I found how to login as admin but it did't solve the issue.

Extend clearInternal() to support clearing a non-default context

DELETE...WHERE... requires the primary key, therefore triples matching a given non-default context have to be fetched with SELECT * WHERE ... ALLOW FILTERING first and only then deleted by DELETE query.

Naive cardinality estimator for a triple pattern using ScyllaDB's estimates

The approach is inspired by the M. Stocker's work.

The cardinality of a triple pattern (i.e. card(t)) is equal to card(t) = card(s) * card(p) * card(o).

The card(s) is based on an estimate from ScyllaDB which maintains "Number of partitions (estimate)" for each table, so we can count the number of distinct subjects by the number of partitions in the S_POC table. Thus card(s) = card(*) / <number of partitions in S_POC> where card(*) is the total number of triples in triplestore.

Same as card(s), the card(o) is based on the estimate from ScyllaDB for the O_SPC table. Thus card(o) = card(*) / <number of partitions in O_SPC>.

The card(p) is fetched from a separate index where each p has the number of triples containing it. Such index is quite small (e.g. for http://tree.datafabric.cc it's just ~680Kb on disk) and easy to maintain (it's a counter which can be incremented and decremented). But still it's only an estimate if insert the same triple 2 times, then the counter is incremented 2 times as well.

If both p and o are bound, then instead of card(o) we use card(p, o). The card(p, o) denotes the number of triples containing both p and o. It's fetched from a separate index where for each p there is a histogram.

The same way, to estimate the card(*) and in future card(c), a separate index is maintained, similarly to the card(p)'s one.

Limitations:

Assumes independence of the subject, predicate and object cardinalities.
Assumes that each subject and object have the same number of relations.
Doesn't use the cardinality of the context if it's bound, i.e. card(c).
Requires to do nodetool flush after any write to ScyllaDB, so it'd recompute the estimates.

Estimates from ScyllaDB are queried through the JMX API which's also used by nodetool.

Support tracing of query executions

It'd be helpful to have information about the steps which the query executor did and how much time each of them took. A library supporting OpenTracing could be used for that.

Failure while adding RDF

Got the following error (console output) when tried to file through the "Add RDF" functionality:

com.datastax.driver.core.exceptions.InvalidQueryException: Key may not be empty scylla-rdf_1

scylla-rdf_1  | 	at com.datastax.driver.core.exceptions.InvalidQueryException.copy(InvalidQueryException.java:49)
scylla-rdf_1  | 	at com.datastax.driver.core.DriverThrowables.propagateCause(DriverThrowables.java:35)
scylla-rdf_1  | 	at com.datastax.driver.core.DefaultResultSetFuture.getUninterruptibly(DefaultResultSetFuture.java:293)
scylla-rdf_1  | 	at com.datastax.driver.core.AbstractSession.execute(AbstractSession.java:58)
scylla-rdf_1  | 	at cc.datafabric.scyllardf.dao.impl.ScyllaRDFIndexDAO.setNamespace(ScyllaRDFIndexDAO.kt:137)
scylla-rdf_1  | 	at cc.datafabric.scyllardf.sail.ScyllaRDFSailConnection.setNamespaceInternal(ScyllaRDFSailConnection.kt:40)
scylla-rdf_1  | 	at org.eclipse.rdf4j.sail.helpers.AbstractSailConnection.setNamespace(AbstractSailConnection.java:621)
scylla-rdf_1  | 	at org.eclipse.rdf4j.repository.sail.SailRepositoryConnection.setNamespace(SailRepositoryConnection.java:354)
scylla-rdf_1  | 	at org.eclipse.rdf4j.repository.util.RDFInserter.addNamespace(RDFInserter.java:54)
scylla-rdf_1  | 	at org.eclipse.rdf4j.repository.util.AbstractRDFInserter.endRDF(AbstractRDFInserter.java:138)
scylla-rdf_1  | 	at org.eclipse.rdf4j.rio.turtle.TurtleParser.parse(TurtleParser.java:186)
scylla-rdf_1  | 	at org.eclipse.rdf4j.rio.turtle.TurtleParser.parse(TurtleParser.java:130)
scylla-rdf_1  | 	at org.eclipse.rdf4j.repository.util.RDFLoader.loadInputStreamOrReader(RDFLoader.java:241)
scylla-rdf_1  | 	at org.eclipse.rdf4j.repository.util.RDFLoader.load(RDFLoader.java:168)
scylla-rdf_1  | 	at org.eclipse.rdf4j.repository.base.AbstractRepositoryConnection.add(AbstractRepositoryConnection.java:289)
scylla-rdf_1  | 	at org.eclipse.rdf4j.http.server.repository.statements.StatementsController.getAddDataResult(StatementsController.java:398)
scylla-rdf_1  | 	at org.eclipse.rdf4j.http.server.repository.statements.StatementsController.handleRequestInternal(StatementsController.java:117)
scylla-rdf_1  | 	at org.springframework.web.servlet.mvc.AbstractController.handleRequest(AbstractController.java:174)
scylla-rdf_1  | 	at org.springframework.web.servlet.mvc.SimpleControllerHandlerAdapter.handle(SimpleControllerHandlerAdapter.java:50)
scylla-rdf_1  | 	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:967)
scylla-rdf_1  | 	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:901)
scylla-rdf_1  | 	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:970)
scylla-rdf_1  | 	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:872)
scylla-rdf_1  | 	at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
scylla-rdf_1  | 	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:846)
scylla-rdf_1  | 	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:109)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at com.github.ziplet.filter.compression.CompressingFilter.doFilter(CompressingFilter.java:300)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:200)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
scylla-rdf_1  | 	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
scylla-rdf_1  | 	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
scylla-rdf_1  | 	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
scylla-rdf_1  | 	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
scylla-rdf_1  | 	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
scylla-rdf_1  | 	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
scylla-rdf_1  | 	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:836)
scylla-rdf_1  | 	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1839)
scylla-rdf_1  | 	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
scylla-rdf_1  | 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1149)
scylla-rdf_1  | 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:624)
scylla-rdf_1  | 	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
scylla-rdf_1  | 	at java.lang.Thread.run(Thread.java:748)
scylla-rdf_1  | Caused by: com.datastax.driver.core.exceptions.InvalidQueryException: Key may not be empty
scylla-rdf_1  | 	at com.datastax.driver.core.Responses$Error.asException(Responses.java:181)
scylla-rdf_1  | 	at com.datastax.driver.core.DefaultResultSetFuture.onSet(DefaultResultSetFuture.java:215)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler.setFinalResult(RequestHandler.java:228)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler.access$2600(RequestHandler.java:62)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler$SpeculativeExecution.setFinalResult(RequestHandler.java:1005)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler$SpeculativeExecution.onSet(RequestHandler.java:808)
scylla-rdf_1  | 	at com.datastax.driver.core.Connection$Dispatcher.channelRead0(Connection.java:1233)
scylla-rdf_1  | 	at com.datastax.driver.core.Connection$Dispatcher.channelRead0(Connection.java:1151)
scylla-rdf_1  | 	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:286)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:102)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:323)
scylla-rdf_1  | 	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:297)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)
scylla-rdf_1  | 	at com.datastax.driver.core.InboundTrafficMeter.channelRead(InboundTrafficMeter.java:38)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965)
scylla-rdf_1  | 	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:644)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:579)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:496)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:458)
scylla-rdf_1  | 	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:897)
scylla-rdf_1  | 	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
scylla-rdf_1  | 	... 1 common frames omitted

An exception is thrown while querying a subject within a named graph

The query (a kind of) that leads to the exception:

SELECT ?s
WHERE {
    GRAPH <http://example.com/graphname> { 
      ?s a :ClassName . 
    } 
}

The exception:

org.eclipse.rdf4j.query.QueryEvaluationException: java.util.concurrent.ExecutionException: com.datastax.driver.core.exceptions.InvalidQueryException: Invalid null value for clustering key part subject

scylla-rdf_1  | org.eclipse.rdf4j.query.QueryEvaluationException: java.util.concurrent.ExecutionException: com.datastax.driver.core.exceptions.InvalidQueryException: Invalid null value for clustering key part subject
scylla-rdf_1  | 	at org.eclipse.rdf4j.sail.evaluation.SailTripleSource$1.convert(SailTripleSource.java:49)
scylla-rdf_1  | 	at org.eclipse.rdf4j.sail.evaluation.SailTripleSource$1.convert(SailTripleSource.java:45)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.ExceptionConvertingIteration.hasNext(ExceptionConvertingIteration.java:69)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.IterationWrapper.hasNext(IterationWrapper.java:63)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.FilterIteration.findNextElement(FilterIteration.java:74)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.FilterIteration.hasNext(FilterIteration.java:45)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.ConvertingIteration.hasNext(ConvertingIteration.java:62)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.ConvertingIteration.hasNext(ConvertingIteration.java:62)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.IterationWrapper.hasNext(IterationWrapper.java:63)
scylla-rdf_1  | 	at org.eclipse.rdf4j.sail.helpers.SailBaseIteration.hasNext(SailBaseIteration.java:41)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.IterationWrapper.hasNext(IterationWrapper.java:63)
scylla-rdf_1  | 	at org.eclipse.rdf4j.query.QueryResults.report(QueryResults.java:225)
scylla-rdf_1  | 	at org.eclipse.rdf4j.http.server.repository.TupleQueryResultView.renderInternal(TupleQueryResultView.java:99)
scylla-rdf_1  | 	at org.eclipse.rdf4j.http.server.repository.QueryResultView.render(QueryResultView.java:63)
scylla-rdf_1  | 	at org.springframework.web.servlet.DispatcherServlet.render(DispatcherServlet.java:1371)
scylla-rdf_1  | 	at org.springframework.web.servlet.DispatcherServlet.processDispatchResult(DispatcherServlet.java:1117)
scylla-rdf_1  | 	at org.springframework.web.servlet.DispatcherServlet.doDispatch(DispatcherServlet.java:1056)
scylla-rdf_1  | 	at org.springframework.web.servlet.DispatcherServlet.doService(DispatcherServlet.java:942)
scylla-rdf_1  | 	at org.springframework.web.servlet.FrameworkServlet.processRequest(FrameworkServlet.java:1005)
scylla-rdf_1  | 	at org.springframework.web.servlet.FrameworkServlet.doPost(FrameworkServlet.java:908)
scylla-rdf_1  | 	at javax.servlet.http.HttpServlet.service(HttpServlet.java:660)
scylla-rdf_1  | 	at org.springframework.web.servlet.FrameworkServlet.service(FrameworkServlet.java:882)
scylla-rdf_1  | 	at javax.servlet.http.HttpServlet.service(HttpServlet.java:741)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:231)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at org.apache.tomcat.websocket.server.WsFilter.doFilter(WsFilter.java:53)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at org.apache.catalina.filters.SetCharacterEncodingFilter.doFilter(SetCharacterEncodingFilter.java:109)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at com.github.ziplet.filter.compression.CompressingFilter.doFilter(CompressingFilter.java:300)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:193)
scylla-rdf_1  | 	at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:166)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:202)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:96)
scylla-rdf_1  | 	at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:490)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:139)
scylla-rdf_1  | 	at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:92)
scylla-rdf_1  | 	at org.apache.catalina.valves.AbstractAccessLogValve.invoke(AbstractAccessLogValve.java:678)
scylla-rdf_1  | 	at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:74)
scylla-rdf_1  | 	at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:343)
scylla-rdf_1  | 	at org.apache.coyote.http11.Http11Processor.service(Http11Processor.java:408)
scylla-rdf_1  | 	at org.apache.coyote.AbstractProcessorLight.process(AbstractProcessorLight.java:66)
scylla-rdf_1  | 	at org.apache.coyote.AbstractProtocol$ConnectionHandler.process(AbstractProtocol.java:853)
scylla-rdf_1  | 	at org.apache.tomcat.util.net.NioEndpoint$SocketProcessor.doRun(NioEndpoint.java:1587)
scylla-rdf_1  | 	at org.apache.tomcat.util.net.SocketProcessorBase.run(SocketProcessorBase.java:49)
scylla-rdf_1  | 	at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
scylla-rdf_1  | 	at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
scylla-rdf_1  | 	at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61)
scylla-rdf_1  | 	at java.base/java.lang.Thread.run(Thread.java:834)
scylla-rdf_1  | Caused by: java.util.concurrent.ExecutionException: com.datastax.driver.core.exceptions.InvalidQueryException: Invalid null value for clustering key part subject
scylla-rdf_1  | 	at com.google.common.util.concurrent.AbstractFuture$Sync.getValue(AbstractFuture.java:299)
scylla-rdf_1  | 	at com.google.common.util.concurrent.AbstractFuture$Sync.get(AbstractFuture.java:286)
scylla-rdf_1  | 	at com.google.common.util.concurrent.AbstractFuture.get(AbstractFuture.java:116)
scylla-rdf_1  | 	at cc.datafabric.scyllardf.dao.MultipleResultSetFutureIteration.hasNext(MultipleResultSetFutureIteration.kt:38)
scylla-rdf_1  | 	at cc.datafabric.scyllardf.dao.SPOCIteration.hasNext(SPOCIteration.kt:22)
scylla-rdf_1  | 	at cc.datafabric.scyllardf.coder.CoderFacade$toStatementIteration$1.hasNext(CoderFacade.kt:222)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.IterationWrapper.hasNext(IterationWrapper.java:63)
scylla-rdf_1  | 	at org.eclipse.rdf4j.sail.helpers.SailBaseIteration.hasNext(SailBaseIteration.java:41)
scylla-rdf_1  | 	at org.eclipse.rdf4j.common.iteration.ExceptionConvertingIteration.hasNext(ExceptionConvertingIteration.java:63)
scylla-rdf_1  | 	... 48 common frames omitted
scylla-rdf_1  | Caused by: com.datastax.driver.core.exceptions.InvalidQueryException: Invalid null value for clustering key part subject
scylla-rdf_1  | 	at com.datastax.driver.core.Responses$Error.asException(Responses.java:181)
scylla-rdf_1  | 	at com.datastax.driver.core.DefaultResultSetFuture.onSet(DefaultResultSetFuture.java:215)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler.setFinalResult(RequestHandler.java:229)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler.access$2600(RequestHandler.java:63)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler$SpeculativeExecution.setFinalResult(RequestHandler.java:1011)
scylla-rdf_1  | 	at com.datastax.driver.core.RequestHandler$SpeculativeExecution.onSet(RequestHandler.java:814)
scylla-rdf_1  | 	at com.datastax.driver.core.Connection$Dispatcher.channelRead0(Connection.java:1286)
scylla-rdf_1  | 	at com.datastax.driver.core.Connection$Dispatcher.channelRead0(Connection.java:1204)
scylla-rdf_1  | 	at io.netty.channel.SimpleChannelInboundHandler.channelRead(SimpleChannelInboundHandler.java:105)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.handler.timeout.IdleStateHandler.channelRead(IdleStateHandler.java:286)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.handler.codec.MessageToMessageDecoder.channelRead(MessageToMessageDecoder.java:102)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.handler.codec.ByteToMessageDecoder.fireChannelRead(ByteToMessageDecoder.java:323)
scylla-rdf_1  | 	at io.netty.handler.codec.ByteToMessageDecoder.channelRead(ByteToMessageDecoder.java:297)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.channel.ChannelInboundHandlerAdapter.channelRead(ChannelInboundHandlerAdapter.java:86)
scylla-rdf_1  | 	at com.datastax.driver.core.InboundTrafficMeter.channelRead(InboundTrafficMeter.java:38)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.fireChannelRead(AbstractChannelHandlerContext.java:340)
scylla-rdf_1  | 	at io.netty.channel.DefaultChannelPipeline$HeadContext.channelRead(DefaultChannelPipeline.java:1434)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:362)
scylla-rdf_1  | 	at io.netty.channel.AbstractChannelHandlerContext.invokeChannelRead(AbstractChannelHandlerContext.java:348)
scylla-rdf_1  | 	at io.netty.channel.DefaultChannelPipeline.fireChannelRead(DefaultChannelPipeline.java:965)
scylla-rdf_1  | 	at io.netty.channel.nio.AbstractNioByteChannel$NioByteUnsafe.read(AbstractNioByteChannel.java:163)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:644)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:579)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:496)
scylla-rdf_1  | 	at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:458)
scylla-rdf_1  | 	at io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:897)
scylla-rdf_1  | 	at io.netty.util.concurrent.FastThreadLocalRunnable.run(FastThreadLocalRunnable.java:30)
scylla-rdf_1  | 	... 1 common frames omitted