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Jena is a Java framework for building Semantic Web applications. It provides a programmatic environment for RDF, RDFS and OWL, SPARQL and includes a rule-based inference engine.
/*
* (c) Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Hewlett-Packard Development Company, LP
* [see end of file]
*/
package com.hp.hpl.jena.db.impl;
import java.util.Iterator;
import java.util.List;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import com.hp.hpl.jena.graph.Node;
import com.hp.hpl.jena.graph.query.Domain;
import com.hp.hpl.jena.graph.query.Element;
import com.hp.hpl.jena.graph.query.Expression;
import com.hp.hpl.jena.graph.query.ExpressionSet;
import com.hp.hpl.jena.graph.query.Fixed;
import com.hp.hpl.jena.shared.JenaException;
import com.hp.hpl.jena.vocabulary.RDF;
/**
@author kers
PatternStageCompiler serves two purposes: it contains the standard algorithm
for compiling patterns-as-triples to patterns-as-Pattern(s), and it has the
standard implementation of PatternCompiler in terms of ordinary Elements.
*/
public final class DBQueryStageCompiler
{
protected static Logger logger = LoggerFactory.getLogger( DBQueryStageCompiler.class );
public DBQueryStageCompiler()
{}
/**
to compile an array of triples, compile each triple and form the corresponding
array of Patterns. *preserve the order*.
*/
public static DBQuery compile
( DBQueryStageCompiler compiler, DBQueryHandler qh, SpecializedGraph sg,
List varList, List dbPat, ExpressionSet constraints )
{
DBQuery query = new DBQuery( sg,varList,qh.queryOnlyStmt, qh.queryOnlyReif,qh.queryFullReif );
if ( qh.getQueryOnlyReified() && !qh.getQueryFullReified() )
throw new JenaException("Fastpath currently requires QueryFullReified to be true if QueryOnlyReified is also true");
if (!query.isEmpty)
{
for (int i = 0; i < dbPat.size(); i += 1) compilePattern ( compiler, query, dbPat.get(i) );
compileConstraints( compiler, query, constraints );
compileQuery( compiler, query );
}
if (logger.isDebugEnabled()) logger.debug( "generated SQL: " + query.stmt );
return query;
}
/**
compile a triple pattern.
*/
private static void compilePattern( DBQueryStageCompiler compiler, DBQuery query,
DBPattern dbpat )
{
Element subj = dbpat.S;
Element obj = dbpat.O;
Element pred = dbpat.P;
String qual = "";
int alias = query.aliasCnt;
if ( query.isReifier ) {
boolean newAlias = true;
if ( !(pred instanceof Fixed) ) throw new JenaException("Reifier predicate not bound");
Node p = ((Fixed) pred).asNodeMatch( (Domain) null );
char reifProp = getReificationChar( p );
if ( !subj.equals(Element.ANY) ) {
// optionally do join optimization for reification.
// if the subject is joined with another pattern and
// that subject is already bound, skip the join.
if ( query.qryFullReif && (subj instanceof Free) &&
query.getBinding(((Free)subj).getListing()).isBoundToCol() ) {
alias = (query.getBinding(((Free)subj).getListing())).alias;
newAlias = false;
} else
qual = query.sqlAnd.gen(getQual(query,alias,'N',subj));
}
qual += query.sqlAnd.gen(getQual(query,alias,reifProp,obj));
qual += query.sqlAnd.gen(query.driver.genSQLQualGraphId(alias,query.graphId));
if ( newAlias ) query.newAlias();
} else {
// query over triple table
qual = query.sqlAnd.gen(getQual(query,alias,'S',subj));
qual += query.sqlAnd.gen(getQual(query,alias,'P',pred));
qual += query.sqlAnd.gen(getQual(query,alias,'O',obj));
qual += query.sqlAnd.gen(query.driver.genSQLQualGraphId(alias,query.graphId));
query.newAlias();
}
query.stmt += qual;
}
/**
Answer the character S, P, O, or T which describes this predicate node.
Throw an exception if it's not one of rdf: subject/predicate/object/type.
@param p the predicate node to be tested
@return the (manky) character code
*/
private static char getReificationChar( Node p )
{
if (p.equals( RDF.Nodes.subject) ) return 'S';
else if ( p.equals( RDF.Nodes.predicate ) ) return 'P';
else if ( p.equals( RDF.Nodes.object ) ) return 'O';
else if ( p.equals( RDF.Nodes.type ) ) return 'T';
else throw new JenaException( "Unexpected reifier predicate: " + p );
}
private static String getQual(DBQuery query,int alias,char pred, Element spo) {
String qual = "";
if (spo instanceof Fixed) {
Node obj = ((Fixed) spo).asNodeMatch((Domain) null);
if ( query.isReifier )
qual = query.driver.genSQLReifQualConst(alias,pred,obj);
else
qual = query.driver.genSQLQualConst(alias,pred,obj);
} else if (spo instanceof Free){
Free v = (Free) spo;
VarDesc bind = query.getBinding(v.getListing());
// only bind to argument value for first use of variable.
// subsequent references should join to first binding.
if ( v.isArg() && !bind.isBoundToCol ) {
query.argCnt++;
query.argType += pred;
query.argIndex.add(new Integer(v.getMapping()));
qual = query.driver.genSQLQualParam(alias, pred);
bind.bindToCol(alias, pred);
} else {
if (bind.isBoundToCol()) {
qual =
query.driver.genSQLJoin( bind.alias, bind.column,
alias, pred);
} else {
// nothing to compare. just binding the var to the column
bind.bindToCol(alias, pred);
qual = "";
}
}
} else if ( spo != Element.ANY )
throw new JenaException("Invalid Element in qualifier");
return qual;
}
/**
compile the constraints.
*/
private static void compileConstraints ( DBQueryStageCompiler compiler, DBQuery query, ExpressionSet constraints )
{
Iterator it = constraints.iterator();
while (it.hasNext())
{
Expression e = it.next();
VarDesc bind = query.findBinding( e.getArg(0).getName() );
if ( bind == null ) throw new JenaException( "Unbound variable in constraint" );
String strMat = ((Expression.Fixed) e.getArg(1)).toString();
query.stmt += query.sqlAnd.gen
( query.driver.genSQLStringMatch( bind.alias, bind.column, e.getFun(), strMat ) );
}
}
/**
compile the final form of the query statement.
*/
private static void compileQuery( DBQueryStageCompiler compiler, DBQuery query )
{
// create result list
int resCnt = query.vars.length - query.argCnt;
query.resList = new int[resCnt];
query.stmt = query.driver.genSQLSelectStmt(
query.driver.genSQLResList(query.resList,query.vars),
query.driver.genSQLFromList(query.aliasCnt,query.table),
query.stmt);
}
}
/*
* (c) Copyright 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Hewlett-Packard Development Company, LP
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions
* are met:
* 1. Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* 2. Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* 3. The name of the author may not be used to endorse or promote products
* derived from this software without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
* IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
* IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
* INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
* NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
* THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/