org.apache.calcite.rel.RelCollations.java Source code

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Here is the source code for org.apache.calcite.rel.RelCollations.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.apache.calcite.rel;

import org.apache.calcite.rel.type.RelDataType;
import org.apache.calcite.util.ImmutableIntList;

import com.google.common.base.Function;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;

import java.util.Iterator;
import java.util.List;

/**
 * Utilities concerning {@link org.apache.calcite.rel.RelCollation}
 * and {@link org.apache.calcite.rel.RelFieldCollation}.
 */
public class RelCollations {
    /**
     * A collation indicating that a relation is not sorted. Ordering by no
     * columns.
     */
    public static final RelCollation EMPTY = RelCollationTraitDef.INSTANCE
            .canonize(new RelCollationImpl(ImmutableList.<RelFieldCollation>of()));

    /**
     * A collation that cannot be replicated by applying a sort. The only
     * implementation choice is to apply operations that preserve order.
     */
    @Deprecated // to be removed before 2.0
    public static final RelCollation PRESERVE = RelCollationTraitDef.INSTANCE
            .canonize(new RelCollationImpl(ImmutableList.of(new RelFieldCollation(-1))) {
                public String toString() {
                    return "PRESERVE";
                }
            });

    private RelCollations() {
    }

    public static RelCollation of(RelFieldCollation... fieldCollations) {
        return new RelCollationImpl(ImmutableList.copyOf(fieldCollations));
    }

    public static RelCollation of(List<RelFieldCollation> fieldCollations) {
        return new RelCollationImpl(ImmutableList.copyOf(fieldCollations));
    }

    /**
     * Creates a collation containing one field.
     */
    public static RelCollation of(int fieldIndex) {
        return of(new RelFieldCollation(fieldIndex));
    }

    /**
     * Creates a list containing one collation containing one field.
     */
    public static List<RelCollation> createSingleton(int fieldIndex) {
        return ImmutableList.of(of(fieldIndex));
    }

    /**
     * Checks that a collection of collations is valid.
     *
     * @param rowType       Row type of the relational expression
     * @param collationList List of collations
     * @param fail          Whether to fail if invalid
     * @return Whether valid
     */
    public static boolean isValid(RelDataType rowType, List<RelCollation> collationList, boolean fail) {
        final int fieldCount = rowType.getFieldCount();
        for (RelCollation collation : collationList) {
            for (RelFieldCollation fieldCollation : collation.getFieldCollations()) {
                final int index = fieldCollation.getFieldIndex();
                if (index < 0 || index >= fieldCount) {
                    assert !fail;
                    return false;
                }
            }
        }
        return true;
    }

    public static boolean equal(List<RelCollation> collationList1, List<RelCollation> collationList2) {
        return collationList1.equals(collationList2);
    }

    /** Returns the indexes of the field collations in a given collation. */
    public static List<Integer> ordinals(RelCollation collation) {
        return Lists.transform(collation.getFieldCollations(), new Function<RelFieldCollation, Integer>() {
            public Integer apply(RelFieldCollation input) {
                return input.getFieldIndex();
            }
        });
    }

    /** Returns whether a collation indicates that the collection is sorted on
     * a given list of keys.
     *
     * @param collation Collation
     * @param keys List of keys
     * @return Whether the collection is sorted on the given keys
     */
    public static boolean contains(RelCollation collation, Iterable<Integer> keys) {
        final int n = collation.getFieldCollations().size();
        final Iterator<Integer> iterator = keys.iterator();
        for (int i = 0; i < n; i++) {
            final RelFieldCollation fieldCollation = collation.getFieldCollations().get(i);
            if (!iterator.hasNext()) {
                return true;
            }
            if (fieldCollation.getFieldIndex() != iterator.next()) {
                return false;
            }
        }
        return !iterator.hasNext();
    }

    /** Returns whether one of a list of collations indicates that the collection
     * is sorted on the given list of keys. */
    public static boolean contains(List<RelCollation> collations, ImmutableIntList keys) {
        for (RelCollation collation : collations) {
            if (contains(collation, keys)) {
                return true;
            }
        }
        return false;
    }

    public static RelCollation shift(RelCollation collation, int offset) {
        if (offset == 0) {
            return collation; // save some effort
        }
        final ImmutableList.Builder<RelFieldCollation> fieldCollations = ImmutableList.builder();
        for (RelFieldCollation fc : collation.getFieldCollations()) {
            fieldCollations.add(fc.shift(offset));
        }
        return new RelCollationImpl(fieldCollations.build());
    }
}

// End RelCollations.java