| /* |
| * Copyright 2009-2010 by The Regents of the University of California |
| * Licensed 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 from |
| * |
| * 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, |
| * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| * See the License for the specific language governing permissions and |
| * limitations under the License. |
| */ |
| package edu.uci.ics.hyracks.algebricks.core.algebra.operators.logical; |
| |
| import java.util.ArrayList; |
| import java.util.List; |
| |
| import edu.uci.ics.hyracks.algebricks.common.exceptions.AlgebricksException; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.ILogicalExpression; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalOperatorTag; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.base.LogicalVariable; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.properties.VariablePropagationPolicy; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.typing.ITypingContext; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.visitors.ILogicalExpressionReferenceTransform; |
| import edu.uci.ics.hyracks.algebricks.core.algebra.visitors.ILogicalOperatorVisitor; |
| |
| public class EmptyTupleSourceOperator extends AbstractLogicalOperator { |
| |
| // public final static EmptyTupleSourceOperator INSTANCE = new |
| // EmptyTupleSourceOperator(); |
| |
| public EmptyTupleSourceOperator() { |
| } |
| |
| @Override |
| public LogicalOperatorTag getOperatorTag() { |
| return LogicalOperatorTag.EMPTYTUPLESOURCE; |
| } |
| |
| @Override |
| public VariablePropagationPolicy getVariablePropagationPolicy() { |
| return VariablePropagationPolicy.NONE; |
| } |
| |
| @Override |
| public boolean acceptExpressionTransform(ILogicalExpressionReferenceTransform visitor) { |
| // do nothing |
| return false; |
| } |
| |
| @Override |
| public <R, T> R accept(ILogicalOperatorVisitor<R, T> visitor, T arg) throws AlgebricksException { |
| return visitor.visitEmptyTupleSourceOperator(this, arg); |
| } |
| |
| @Override |
| public void recomputeSchema() { |
| schema = new ArrayList<LogicalVariable>(); |
| } |
| |
| @Override |
| public boolean isMap() { |
| return false; |
| } |
| |
| @Override |
| public IVariableTypeEnvironment computeOutputTypeEnvironment(final ITypingContext ctx) throws AlgebricksException { |
| return new IVariableTypeEnvironment() { |
| |
| @Override |
| public void setVarType(LogicalVariable var, Object type) { |
| throw new IllegalStateException(); |
| } |
| |
| @Override |
| public Object getVarType(LogicalVariable var) throws AlgebricksException { |
| return null; |
| } |
| |
| @Override |
| public Object getType(ILogicalExpression expr) throws AlgebricksException { |
| return ctx.getExpressionTypeComputer().getType(expr, ctx.getMetadataProvider(), this); |
| } |
| |
| @Override |
| public Object getVarType(LogicalVariable var, List<LogicalVariable> nonNullVariables) |
| throws AlgebricksException { |
| return null; |
| } |
| |
| @Override |
| public boolean substituteProducedVariable(LogicalVariable v1, LogicalVariable v2) |
| throws AlgebricksException { |
| return false; |
| } |
| }; |
| } |
| |
| } |