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SDB is a persistence layer for use with Apache Jena that uses an SQL database to store triples/quads.

There is a newer version: 3.17.0

/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
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 * See the License for the specific language governing permissions and
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package org.apache.jena.sdb.compiler;

import org.apache.jena.sparql.algebra.Op ;
import org.apache.jena.sparql.algebra.TransformCopy ;
import org.apache.jena.sparql.algebra.op.OpProject ;
import org.apache.jena.sparql.algebra.op.OpSlice ;

public class TransformSliceProject extends TransformCopy
{
    @Override
    public Op transform(OpSlice opSlice, Op subOp)
    {
        // (slice (project...)) ==> (project (slice ...))
        if ( subOp instanceof OpProject )
        {
            OpProject p = (OpProject)subOp ;
            Op sub = p.getSubOp() ;
            
            Op x = new OpSlice(sub, opSlice.getStart(), opSlice.getLength()) ;
            x = new OpProject(x, p.getVars()) ;
            return x ;
        }
        
        return super.transform(opSlice, subOp) ;
    }
}