hivesterix/src/main/java/edu/uci/ics/hivesterix/logical/plan/visitor/LimitVisitor.java

package edu.uci.ics.hivesterix.logical.plan.visitor;

import java.util.List;

import org.apache.commons.lang3.mutable.Mutable;
import org.apache.commons.lang3.mutable.MutableObject;
import org.apache.hadoop.hive.ql.exec.LimitOperator;
import org.apache.hadoop.hive.ql.plan.LimitDesc;

import edu.uci.ics.hivesterix.logical.expression.HivesterixConstantValue;
import edu.uci.ics.hivesterix.logical.expression.Schema;
import edu.uci.ics.hivesterix.logical.plan.visitor.base.DefaultVisitor;
import edu.uci.ics.hivesterix.logical.plan.visitor.base.Translator;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalExpression;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalOperator;
import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalVariable;
import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.ConstantExpression;

public class LimitVisitor extends DefaultVisitor {

	@Override
	public Mutable<ILogicalOperator> visit(LimitOperator operator,
			Mutable<ILogicalOperator> AlgebricksParentOperatorRef, Translator t) {
		Schema currentSchema = t.generateInputSchema(operator
				.getParentOperators().get(0));

		LimitDesc desc = (LimitDesc) operator.getConf();
		int limit = desc.getLimit();
		Integer limitValue = new Integer(limit);

		ILogicalExpression expr = new ConstantExpression(
				new HivesterixConstantValue(limitValue));
		ILogicalOperator currentOperator = new edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical.LimitOperator(
				expr, true);
		currentOperator.getInputs().add(AlgebricksParentOperatorRef);

		operator.setSchema(operator.getParentOperators().get(0).getSchema());
		List<LogicalVariable> latestOutputSchema = t
				.getVariablesFromSchema(currentSchema);
		t.rewriteOperatorOutputSchema(latestOutputSchema, operator);
		return new MutableObject<ILogicalOperator>(currentOperator);
	}

}