algebricks/algebricks-core/src/main/java/org/apache/hyracks/algebricks/core/algebra/properties/TypePropagationPolicy.java

/*
 * 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, 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.
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package org.apache.hyracks.algebricks.core.algebra.properties;

import java.util.List;

import org.apache.hyracks.algebricks.common.exceptions.AlgebricksException;
import org.apache.hyracks.algebricks.core.algebra.base.LogicalVariable;
import org.apache.hyracks.algebricks.core.algebra.expressions.INullableTypeComputer;
import org.apache.hyracks.algebricks.core.algebra.expressions.IVariableTypeEnvironment;
import org.apache.hyracks.algebricks.core.algebra.typing.ITypeEnvPointer;

public abstract class TypePropagationPolicy {
    public static final TypePropagationPolicy ALL = new TypePropagationPolicy() {

        @Override
        public Object getVarType(LogicalVariable var, INullableTypeComputer ntc,
                List<LogicalVariable> nonNullVariableList, List<List<LogicalVariable>> correlatedNullableVariableLists,
                ITypeEnvPointer... typeEnvs) throws AlgebricksException {
            for (ITypeEnvPointer p : typeEnvs) {
                IVariableTypeEnvironment env = p.getTypeEnv();
                if (env == null) {
                    throw new AlgebricksException("Null environment for pointer " + p + " in getVarType for var=" + var);
                }
                Object t = env.getVarType(var, nonNullVariableList, correlatedNullableVariableLists);
                if (t != null) {
                    if (ntc != null && ntc.canBeNull(t)) {
                        for (List<LogicalVariable> list : correlatedNullableVariableLists) {
                            if (list.contains(var)) {
                                for (LogicalVariable v : list) {
                                    if (nonNullVariableList.contains(v)) {
                                        return ntc.getNonOptionalType(t);
                                    }
                                }
                            }
                        }
                    }
                    return t;
                }
            }
            return null;
        }
    };

    public static final TypePropagationPolicy LEFT_OUTER = new TypePropagationPolicy() {

        @Override
        public Object getVarType(LogicalVariable var, INullableTypeComputer ntc,
                List<LogicalVariable> nonNullVariableList, List<List<LogicalVariable>> correlatedNullableVariableLists,
                ITypeEnvPointer... typeEnvs) throws AlgebricksException {
            int n = typeEnvs.length;
            for (int i = 0; i < n; i++) {
                Object t = typeEnvs[i].getTypeEnv().getVarType(var, nonNullVariableList,
                        correlatedNullableVariableLists);
                if (t != null) {
                    if (i == 0) { // inner branch
                        return t;
                    } else { // outer branch
                        boolean nonNullVarIsProduced = false;
                        for (LogicalVariable v : nonNullVariableList) {
                            if (v == var) {
                                nonNullVarIsProduced = true;
                                break;
                            }
                            if (typeEnvs[i].getTypeEnv().getVarType(v) != null) {
                                nonNullVarIsProduced = true;
                                break;
                            }
                        }
                        if (nonNullVarIsProduced) {
                            return t;
                        } else {
                            return ntc.makeNullableType(t);
                        }
                    }
                }
            }
            return null;
        }
    };

    public abstract Object getVarType(LogicalVariable var, INullableTypeComputer ntc,
            List<LogicalVariable> nonNullVariableList, List<List<LogicalVariable>> correlatedNullableVariableLists,
            ITypeEnvPointer... typeEnvs) throws AlgebricksException;
}