Java tutorial
/* * 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.cassandra.db; import java.io.IOException; import java.nio.ByteBuffer; import java.util.*; import org.apache.cassandra.db.marshal.AbstractType; import org.apache.cassandra.io.util.DataInputPlus; import org.apache.cassandra.io.util.DataOutputPlus; import org.apache.cassandra.utils.ByteBufferUtil; /** * A slice represents the selection of a range of rows. * <p> * A slice has a start and an end bound that are both (potentially full) clustering prefixes. * A slice selects every rows whose clustering is bigger than the slice start prefix but smaller * than the end prefix. Both start and end can be either inclusive or exclusive. */ public class Slice { public static final Serializer serializer = new Serializer(); /** The slice selecting all rows (of a given partition) */ public static final Slice ALL = new Slice(ClusteringBound.BOTTOM, ClusteringBound.TOP) { @Override public boolean includes(ClusteringComparator comparator, ClusteringPrefix clustering) { return true; } @Override public boolean intersects(ClusteringComparator comparator, List<ByteBuffer> minClusteringValues, List<ByteBuffer> maxClusteringValues) { return true; } @Override public String toString(ClusteringComparator comparator) { return "ALL"; } }; private final ClusteringBound start; private final ClusteringBound end; private Slice(ClusteringBound start, ClusteringBound end) { assert start.isStart() && end.isEnd(); this.start = start; this.end = end; } public static Slice make(ClusteringBound start, ClusteringBound end) { if (start == ClusteringBound.BOTTOM && end == ClusteringBound.TOP) return ALL; return new Slice(start, end); } public static Slice make(ClusteringComparator comparator, Object... values) { CBuilder builder = CBuilder.create(comparator); for (Object val : values) { if (val instanceof ByteBuffer) builder.add((ByteBuffer) val); else builder.add(val); } return new Slice(builder.buildBound(true, true), builder.buildBound(false, true)); } public static Slice make(Clustering clustering) { // This doesn't give us what we want with the clustering prefix assert clustering != Clustering.STATIC_CLUSTERING; ByteBuffer[] values = extractValues(clustering); return new Slice(ClusteringBound.inclusiveStartOf(values), ClusteringBound.inclusiveEndOf(values)); } public static Slice make(Clustering start, Clustering end) { // This doesn't give us what we want with the clustering prefix assert start != Clustering.STATIC_CLUSTERING && end != Clustering.STATIC_CLUSTERING; ByteBuffer[] startValues = extractValues(start); ByteBuffer[] endValues = extractValues(end); return new Slice(ClusteringBound.inclusiveStartOf(startValues), ClusteringBound.inclusiveEndOf(endValues)); } private static ByteBuffer[] extractValues(ClusteringPrefix clustering) { ByteBuffer[] values = new ByteBuffer[clustering.size()]; for (int i = 0; i < clustering.size(); i++) values[i] = clustering.get(i); return values; } public ClusteringBound start() { return start; } public ClusteringBound end() { return end; } public ClusteringBound open(boolean reversed) { return reversed ? end : start; } public ClusteringBound close(boolean reversed) { return reversed ? start : end; } /** * Return whether the slice is empty. * * @param comparator the comparator to compare the bounds. * @return whether the slice formed is empty or not. */ public boolean isEmpty(ClusteringComparator comparator) { return isEmpty(comparator, start(), end()); } /** * Return whether the slice formed by the two provided bound is empty or not. * * @param comparator the comparator to compare the bounds. * @param start the start for the slice to consider. This must be a start bound. * @param end the end for the slice to consider. This must be an end bound. * @return whether the slice formed by {@code start} and {@code end} is * empty or not. */ public static boolean isEmpty(ClusteringComparator comparator, ClusteringBound start, ClusteringBound end) { assert start.isStart() && end.isEnd(); int cmp = comparator.compare(start, end); if (cmp < 0) return false; else if (cmp > 0) return true; else return start.isExclusive() || end.isExclusive(); } /** * Returns whether a given clustering or bound is included in this slice. * * @param comparator the comparator for the table this is a slice of. * @param bound the bound to test inclusion of. * * @return whether {@code bound} is within the bounds of this slice. */ public boolean includes(ClusteringComparator comparator, ClusteringPrefix bound) { return comparator.compare(start, bound) <= 0 && comparator.compare(bound, end) <= 0; } /** * Returns a slice for continuing paging from the last returned clustering prefix. * * @param comparator the comparator for the table this is a filter for. * @param lastReturned the last clustering that was returned for the query we are paging for. The * resulting slices will be such that only results coming stricly after {@code lastReturned} are returned * (where coming after means "greater than" if {@code !reversed} and "lesser than" otherwise). * @param inclusive whether or not we want to include the {@code lastReturned} in the newly returned page of results. * @param reversed whether the query we're paging for is reversed or not. * * @return a new slice that selects results coming after {@code lastReturned}, or {@code null} if paging * the resulting slice selects nothing (i.e. if it originally selects nothing coming after {@code lastReturned}). */ public Slice forPaging(ClusteringComparator comparator, Clustering lastReturned, boolean inclusive, boolean reversed) { if (lastReturned == null) return this; if (reversed) { int cmp = comparator.compare(lastReturned, start); if (cmp < 0 || (!inclusive && cmp == 0)) return null; cmp = comparator.compare(end, lastReturned); if (cmp < 0 || (inclusive && cmp == 0)) return this; ByteBuffer[] values = extractValues(lastReturned); return new Slice(start, inclusive ? ClusteringBound.inclusiveEndOf(values) : ClusteringBound.exclusiveEndOf(values)); } else { int cmp = comparator.compare(end, lastReturned); if (cmp < 0 || (!inclusive && cmp == 0)) return null; cmp = comparator.compare(lastReturned, start); if (cmp < 0 || (inclusive && cmp == 0)) return this; ByteBuffer[] values = extractValues(lastReturned); return new Slice( inclusive ? ClusteringBound.inclusiveStartOf(values) : ClusteringBound.exclusiveStartOf(values), end); } } /** * Given the per-clustering column minimum and maximum value a sstable contains, whether or not this slice potentially * intersects that sstable or not. * * @param comparator the comparator for the table this is a slice of. * @param minClusteringValues the smallest values for each clustering column that a sstable contains. * @param maxClusteringValues the biggest values for each clustering column that a sstable contains. * * @return whether the slice might intersects with the sstable having {@code minClusteringValues} and * {@code maxClusteringValues}. */ public boolean intersects(ClusteringComparator comparator, List<ByteBuffer> minClusteringValues, List<ByteBuffer> maxClusteringValues) { // If this slice starts after max clustering or ends before min clustering, it can't intersect return start.compareTo(comparator, maxClusteringValues) <= 0 && end.compareTo(comparator, minClusteringValues) >= 0; } public String toString(ClusteringComparator comparator) { StringBuilder sb = new StringBuilder(); sb.append(start.isInclusive() ? "[" : "("); for (int i = 0; i < start.size(); i++) { if (i > 0) sb.append(':'); sb.append(comparator.subtype(i).getString(start.get(i))); } sb.append(", "); for (int i = 0; i < end.size(); i++) { if (i > 0) sb.append(':'); sb.append(comparator.subtype(i).getString(end.get(i))); } sb.append(end.isInclusive() ? "]" : ")"); return sb.toString(); } @Override public boolean equals(Object other) { if (!(other instanceof Slice)) return false; Slice that = (Slice) other; return this.start().equals(that.start()) && this.end().equals(that.end()); } @Override public int hashCode() { return Objects.hash(start(), end()); } public static class Serializer { public void serialize(Slice slice, DataOutputPlus out, int version, List<AbstractType<?>> types) throws IOException { ClusteringBound.serializer.serialize(slice.start, out, version, types); ClusteringBound.serializer.serialize(slice.end, out, version, types); } public long serializedSize(Slice slice, int version, List<AbstractType<?>> types) { return ClusteringBound.serializer.serializedSize(slice.start, version, types) + ClusteringBound.serializer.serializedSize(slice.end, version, types); } public Slice deserialize(DataInputPlus in, int version, List<AbstractType<?>> types) throws IOException { ClusteringBound start = (ClusteringBound) ClusteringBound.serializer.deserialize(in, version, types); ClusteringBound end = (ClusteringBound) ClusteringBound.serializer.deserialize(in, version, types); return new Slice(start, end); } } }