org.apache.druid.query.select.PagingSpec.java Source code

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Here is the source code for org.apache.druid.query.select.PagingSpec.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.druid.query.select;

import com.fasterxml.jackson.annotation.JacksonInject;
import com.fasterxml.jackson.annotation.JsonCreator;
import com.fasterxml.jackson.annotation.JsonProperty;
import com.google.common.collect.Maps;
import org.apache.druid.java.util.common.StringUtils;

import java.nio.ByteBuffer;
import java.util.Map;

/**
 */
public class PagingSpec {
    public static PagingSpec newSpec(int threshold) {
        return new PagingSpec(null, threshold);
    }

    public static Map<String, Integer> merge(Iterable<Map<String, Integer>> cursors) {
        Map<String, Integer> next = Maps.newHashMap();
        for (Map<String, Integer> cursor : cursors) {
            for (Map.Entry<String, Integer> entry : cursor.entrySet()) {
                next.put(entry.getKey(), entry.getValue());
            }
        }
        return next;
    }

    public static Map<String, Integer> next(Map<String, Integer> cursor, boolean descending) {
        for (Map.Entry<String, Integer> entry : cursor.entrySet()) {
            entry.setValue(descending ? entry.getValue() - 1 : entry.getValue() + 1);
        }
        return cursor;
    }

    private final Map<String, Integer> pagingIdentifiers;
    private final int threshold;
    private final boolean fromNext;

    @JsonCreator
    public PagingSpec(@JsonProperty("pagingIdentifiers") Map<String, Integer> pagingIdentifiers,
            @JsonProperty("threshold") int threshold, @JsonProperty("fromNext") Boolean fromNext,
            @JacksonInject SelectQueryConfig config) {
        this.pagingIdentifiers = pagingIdentifiers == null ? Maps.newHashMap() : pagingIdentifiers;
        this.threshold = threshold;

        boolean defaultFromNext = config.getEnableFromNextDefault();
        this.fromNext = fromNext == null ? defaultFromNext : fromNext;
    }

    public PagingSpec(Map<String, Integer> pagingIdentifiers, int threshold) {
        this(pagingIdentifiers, threshold, null, new SelectQueryConfig(true));
    }

    public PagingSpec(Map<String, Integer> pagingIdentifiers, int threshold, Boolean fromNext) {
        this(pagingIdentifiers, threshold, fromNext, new SelectQueryConfig(true));
    }

    @JsonProperty
    public Map<String, Integer> getPagingIdentifiers() {
        return pagingIdentifiers;
    }

    @JsonProperty
    public int getThreshold() {
        return threshold;
    }

    @JsonProperty
    public boolean isFromNext() {
        return fromNext;
    }

    public byte[] getCacheKey() {
        final byte[][] pagingKeys = new byte[pagingIdentifiers.size()][];
        final byte[][] pagingValues = new byte[pagingIdentifiers.size()][];

        int index = 0;
        int pagingKeysSize = 0;
        int pagingValuesSize = 0;
        for (Map.Entry<String, Integer> entry : pagingIdentifiers.entrySet()) {
            pagingKeys[index] = StringUtils.toUtf8(entry.getKey());
            pagingValues[index] = ByteBuffer.allocate(Integer.BYTES).putInt(entry.getValue()).array();
            pagingKeysSize += pagingKeys[index].length;
            pagingValuesSize += Integer.BYTES;
            index++;
        }

        final byte[] thresholdBytes = ByteBuffer.allocate(Integer.BYTES).putInt(threshold).array();

        final ByteBuffer queryCacheKey = ByteBuffer
                .allocate(pagingKeysSize + pagingValuesSize + thresholdBytes.length + 1);

        for (byte[] pagingKey : pagingKeys) {
            queryCacheKey.put(pagingKey);
        }

        for (byte[] pagingValue : pagingValues) {
            queryCacheKey.put(pagingValue);
        }

        queryCacheKey.put(thresholdBytes);
        queryCacheKey.put(isFromNext() ? (byte) 0x01 : 0x00);

        return queryCacheKey.array();
    }

    public PagingOffset getOffset(String identifier, boolean descending) {
        Integer offset = pagingIdentifiers.get(identifier);
        if (offset == null) {
            offset = PagingOffset.toOffset(0, descending);
        } else if (fromNext) {
            offset = descending ? offset - 1 : offset + 1;
        }
        return PagingOffset.of(offset, threshold);
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        PagingSpec that = (PagingSpec) o;

        if (fromNext != that.fromNext) {
            return false;
        }
        if (threshold != that.threshold) {
            return false;
        }
        if (!pagingIdentifiers.equals(that.pagingIdentifiers)) {
            return false;
        }

        return true;
    }

    @Override
    public int hashCode() {
        int result = pagingIdentifiers.hashCode();
        result = 31 * result + threshold;
        result = 31 * result + (fromNext ? 1 : 0);
        return result;
    }

    @Override
    public String toString() {
        return "PagingSpec{" + "pagingIdentifiers=" + pagingIdentifiers + ", threshold=" + threshold + ", fromNext="
                + fromNext + '}';
    }
}