org.eigenbase.rex.RexPermuteInputsShuttle.java Source code

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Here is the source code for org.eigenbase.rex.RexPermuteInputsShuttle.java

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/*
 * 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.
 */
package org.eigenbase.rex;

import java.util.List;

import org.eigenbase.rel.RelNode;
import org.eigenbase.reltype.RelDataTypeField;
import org.eigenbase.util.mapping.Mappings;

import com.google.common.collect.ImmutableList;

/**
 * Shuttle which applies a permutation to its input fields.
 *
 * @see RexPermutationShuttle
 * @see RexUtil#apply(org.eigenbase.util.mapping.Mappings.TargetMapping, RexNode)
 */
public class RexPermuteInputsShuttle extends RexShuttle {
    //~ Instance fields --------------------------------------------------------

    private final Mappings.TargetMapping mapping;
    private final ImmutableList<RelDataTypeField> fields;

    //~ Constructors -----------------------------------------------------------

    /**
     * Creates a RexPermuteInputsShuttle.
     *
     * <p>The mapping provides at most one target for every source. If a source
     * has no targets and is referenced in the expression,
     * {@link org.eigenbase.util.mapping.Mappings.TargetMapping#getTarget(int)}
     * will give an error. Otherwise the mapping gives a unique target.
     *
     * @param mapping Mapping
     * @param inputs  Input relational expressions
     */
    public RexPermuteInputsShuttle(Mappings.TargetMapping mapping, RelNode... inputs) {
        this(mapping, fields(inputs));
    }

    private RexPermuteInputsShuttle(Mappings.TargetMapping mapping, ImmutableList<RelDataTypeField> fields) {
        this.mapping = mapping;
        this.fields = fields;
    }

    /** Creates a shuttle with an empty field list. It cannot handle GET calls but
     * otherwise works OK. */
    public static RexPermuteInputsShuttle of(Mappings.TargetMapping mapping) {
        return new RexPermuteInputsShuttle(mapping, ImmutableList.<RelDataTypeField>of());
    }

    //~ Methods ----------------------------------------------------------------

    private static ImmutableList<RelDataTypeField> fields(RelNode[] inputs) {
        final ImmutableList.Builder<RelDataTypeField> fields = ImmutableList.builder();
        for (RelNode input : inputs) {
            fields.addAll(input.getRowType().getFieldList());
        }
        return fields.build();
    }

    @Override
    public RexNode visitInputRef(RexInputRef local) {
        final int index = local.getIndex();
        int target = mapping.getTarget(index);
        return new RexInputRef(target, local.getType());
    }

    @Override
    public RexNode visitCall(RexCall call) {
        if (call.getOperator() == RexBuilder.GET_OPERATOR) {
            final String name = (String) ((RexLiteral) call.getOperands().get(1)).getValue2();
            final int i = lookup(fields, name);
            if (i >= 0) {
                return RexInputRef.of(i, fields);
            }
        }
        return super.visitCall(call);
    }

    private static int lookup(List<RelDataTypeField> fields, String name) {
        for (int i = 0; i < fields.size(); i++) {
            final RelDataTypeField field = fields.get(i);
            if (field.getName().equals(name)) {
                return i;
            }
        }
        return -1;
    }
}

// End RexPermuteInputsShuttle.java