LogicalOlapQueryPlan.java

// (c) 2005 Andreas Harth
package org.olap4j.driver.olap4ld.linkeddata;

import org.olap4j.driver.olap4ld.helper.GraphVizVisualisationVisitor;

/**
 * A query plan. How to encode the plan is not yet clear is a plan constructed
 * out of a program or a rule? What happens to the program that is the answer to
 * a query and what to the program that is the "background knowledge"?
 * 
 * @author aharth
 */
public class LogicalOlapQueryPlan {
	// root of the plan (might be arraylist in case there's a forrest/union/cart
	// product)
	LogicalOlapOp _root = null;

	/**
	 * Constructor.
	 */
	public LogicalOlapQueryPlan(LogicalOlapOp root) {
		_root = root;
	}

	public String toString() {
		if (_root != null)
			return _root.toString();

		return null;
	}

	/**
	 * Generate the query plan (cascading iterators) based on the plan and the
	 * Lexicon and the QuadIndex.
	 * 
	 * Return a list of variable bindings in clear text. Maybe should have
	 * something to return a list of statements as well (need to find out why
	 * conjunctions are not allowed in the head).
	 */
	/*
	 * public ValuesIterator generateIterator(Lexicon lex, QuadIndex quads)
	 * throws IOException { return new ValuesIterator(lex, _root.iterator(lex,
	 * quads)); }
	 */

	public String toXML() throws QueryException {
		// LogicalOlapQueryPlan2Xml rel2xml = new LogicalOlapQueryPlan2Xml();
		// _root.accept(rel2xml);
		//
		// return (String)rel2xml.getNewRoot();
		return null;
	}
	
	public String toDOT() throws QueryException {
		// Store dot notation
		GraphVizVisualisationVisitor graphvizvisitor = new GraphVizVisualisationVisitor();
		_root.accept(graphvizvisitor);
		
		return (String) graphvizvisitor.getNewRoot();
		
	}

	/**
	 * Entry method that visits all nodes recursively and returns the root of
	 * the transformed tree.
	 */
	public Object visitAll(LogicalOlapOperatorQueryPlanVisitor v)
			throws QueryException {
		_root.accept(v);

		return v.getNewRoot();
	}
}