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.rows; import java.io.IOException; import java.nio.ByteBuffer; import java.util.Comparator; import org.apache.cassandra.config.*; import org.apache.cassandra.db.*; import org.apache.cassandra.io.util.DataOutputPlus; import org.apache.cassandra.io.util.DataInputPlus; import org.apache.cassandra.schema.ColumnMetadata; import org.apache.cassandra.utils.ByteBufferUtil; import org.apache.cassandra.utils.memory.AbstractAllocator; /** * A cell is our atomic unit for a single value of a single column. * <p> * A cell always holds at least a timestamp that gives us how the cell reconcile. We then * have 3 main types of cells: * 1) live regular cells: those will also have a value and, if for a complex column, a path. * 2) expiring cells: on top of regular cells, those have a ttl and a local deletion time (when they are expired). * 3) tombstone cells: those won't have value, but they have a local deletion time (when the tombstone was created). */ public abstract class Cell extends ColumnData { public static final int NO_TTL = 0; public static final int NO_DELETION_TIME = Integer.MAX_VALUE; public static final int MAX_DELETION_TIME = Integer.MAX_VALUE - 1; public final static Comparator<Cell> comparator = (c1, c2) -> { int cmp = c1.column().compareTo(c2.column()); if (cmp != 0) return cmp; Comparator<CellPath> pathComparator = c1.column().cellPathComparator(); return pathComparator == null ? 0 : pathComparator.compare(c1.path(), c2.path()); }; public static final Serializer serializer = new BufferCell.Serializer(); protected Cell(ColumnMetadata column) { super(column); } /** * Whether the cell is a counter cell or not. * * @return whether the cell is a counter cell or not. */ public abstract boolean isCounterCell(); /** * The cell value. * * @return the cell value. */ public abstract ByteBuffer value(); /** * The cell timestamp. * <p> * @return the cell timestamp. */ public abstract long timestamp(); /** * The cell ttl. * * @return the cell ttl, or {@code NO_TTL} if the cell isn't an expiring one. */ public abstract int ttl(); /** * The cell local deletion time. * * @return the cell local deletion time, or {@code NO_DELETION_TIME} if the cell is neither * a tombstone nor an expiring one. */ public abstract int localDeletionTime(); /** * Whether the cell is a tombstone or not. * * @return whether the cell is a tombstone or not. */ public abstract boolean isTombstone(); /** * Whether the cell is an expiring one or not. * <p> * Note that this only correspond to whether the cell liveness info * have a TTL or not, but doesn't tells whether the cell is already expired * or not. You should use {@link #isLive} for that latter information. * * @return whether the cell is an expiring one or not. */ public abstract boolean isExpiring(); /** * Whether the cell is live or not given the current time. * * @param nowInSec the current time in seconds. This is used to * decide if an expiring cell is expired or live. * @return whether the cell is live or not at {@code nowInSec}. */ public abstract boolean isLive(int nowInSec); /** * For cells belonging to complex types (non-frozen collection and UDT), the * path to the cell. * * @return the cell path for cells of complex column, and {@code null} for other cells. */ public abstract CellPath path(); public abstract Cell withUpdatedColumn(ColumnMetadata newColumn); public abstract Cell withUpdatedValue(ByteBuffer newValue); public abstract Cell withUpdatedTimestampAndLocalDeletionTime(long newTimestamp, int newLocalDeletionTime); public abstract Cell copy(AbstractAllocator allocator); @Override // Overrides super type to provide a more precise return type. public abstract Cell markCounterLocalToBeCleared(); @Override // Overrides super type to provide a more precise return type. public abstract Cell purge(DeletionPurger purger, int nowInSec); /** * The serialization format for cell is: * [ flags ][ timestamp ][ deletion time ][ ttl ][ path size ][ path ][ value size ][ value ] * [ 1b ][ 8b (vint) ][ 4b (vint) ][ 4b (vint) ][ 4b (vint) ][ arb ][ 4b (vint) ][ arb ] * * where not all field are always present (in fact, only the [ flags ] are guaranteed to be present). The fields have the following * meaning: * - [ flags ] is the cell flags. It is a byte for which each bit represents a flag whose meaning is explained below (*_MASK constants) * - [ timestamp ] is the cell timestamp. Present unless the cell has the USE_TIMESTAMP_MASK. * - [ deletion time]: the local deletion time for the cell. Present if either the cell is deleted (IS_DELETED_MASK) * or it is expiring (IS_EXPIRING_MASK) but doesn't have the USE_ROW_TTL_MASK. * - [ ttl ]: the ttl for the cell. Present if the row is expiring (IS_EXPIRING_MASK) but doesn't have the * USE_ROW_TTL_MASK. * - [ value size ] is the size of the [ value ] field. It's present unless either the cell has the HAS_EMPTY_VALUE_MASK, or the value * for columns of this type have a fixed length. * - [ path size ] is the size of the [ path ] field. Present iff this is the cell of a complex column. * - [ value ]: the cell value, unless it has the HAS_EMPTY_VALUE_MASK. * - [ path ]: the cell path if the column this is a cell of is complex. */ static class Serializer { private final static int IS_DELETED_MASK = 0x01; // Whether the cell is a tombstone or not. private final static int IS_EXPIRING_MASK = 0x02; // Whether the cell is expiring. private final static int HAS_EMPTY_VALUE_MASK = 0x04; // Wether the cell has an empty value. This will be the case for tombstone in particular. private final static int USE_ROW_TIMESTAMP_MASK = 0x08; // Wether the cell has the same timestamp than the row this is a cell of. private final static int USE_ROW_TTL_MASK = 0x10; // Wether the cell has the same ttl than the row this is a cell of. public void serialize(Cell cell, ColumnMetadata column, DataOutputPlus out, LivenessInfo rowLiveness, SerializationHeader header) throws IOException { assert cell != null; boolean hasValue = cell.value().hasRemaining(); boolean isDeleted = cell.isTombstone(); boolean isExpiring = cell.isExpiring(); boolean useRowTimestamp = !rowLiveness.isEmpty() && cell.timestamp() == rowLiveness.timestamp(); boolean useRowTTL = isExpiring && rowLiveness.isExpiring() && cell.ttl() == rowLiveness.ttl() && cell.localDeletionTime() == rowLiveness.localExpirationTime(); int flags = 0; if (!hasValue) flags |= HAS_EMPTY_VALUE_MASK; if (isDeleted) flags |= IS_DELETED_MASK; else if (isExpiring) flags |= IS_EXPIRING_MASK; if (useRowTimestamp) flags |= USE_ROW_TIMESTAMP_MASK; if (useRowTTL) flags |= USE_ROW_TTL_MASK; out.writeByte((byte) flags); if (!useRowTimestamp) header.writeTimestamp(cell.timestamp(), out); if ((isDeleted || isExpiring) && !useRowTTL) header.writeLocalDeletionTime(cell.localDeletionTime(), out); if (isExpiring && !useRowTTL) header.writeTTL(cell.ttl(), out); if (column.isComplex()) column.cellPathSerializer().serialize(cell.path(), out); if (hasValue) header.getType(column).writeValue(cell.value(), out); } public Cell deserialize(DataInputPlus in, LivenessInfo rowLiveness, ColumnMetadata column, SerializationHeader header, SerializationHelper helper) throws IOException { int flags = in.readUnsignedByte(); boolean hasValue = (flags & HAS_EMPTY_VALUE_MASK) == 0; boolean isDeleted = (flags & IS_DELETED_MASK) != 0; boolean isExpiring = (flags & IS_EXPIRING_MASK) != 0; boolean useRowTimestamp = (flags & USE_ROW_TIMESTAMP_MASK) != 0; boolean useRowTTL = (flags & USE_ROW_TTL_MASK) != 0; long timestamp = useRowTimestamp ? rowLiveness.timestamp() : header.readTimestamp(in); int localDeletionTime = useRowTTL ? rowLiveness.localExpirationTime() : (isDeleted || isExpiring ? header.readLocalDeletionTime(in) : NO_DELETION_TIME); int ttl = useRowTTL ? rowLiveness.ttl() : (isExpiring ? header.readTTL(in) : NO_TTL); CellPath path = column.isComplex() ? column.cellPathSerializer().deserialize(in) : null; ByteBuffer value = ByteBufferUtil.EMPTY_BYTE_BUFFER; if (hasValue) { if (helper.canSkipValue(column) || (path != null && helper.canSkipValue(path))) { header.getType(column).skipValue(in); } else { boolean isCounter = localDeletionTime == NO_DELETION_TIME && column.type.isCounter(); value = header.getType(column).readValue(in, DatabaseDescriptor.getMaxValueSize()); if (isCounter) value = helper.maybeClearCounterValue(value); } } return new BufferCell(column, timestamp, ttl, localDeletionTime, value, path); } public long serializedSize(Cell cell, ColumnMetadata column, LivenessInfo rowLiveness, SerializationHeader header) { long size = 1; // flags boolean hasValue = cell.value().hasRemaining(); boolean isDeleted = cell.isTombstone(); boolean isExpiring = cell.isExpiring(); boolean useRowTimestamp = !rowLiveness.isEmpty() && cell.timestamp() == rowLiveness.timestamp(); boolean useRowTTL = isExpiring && rowLiveness.isExpiring() && cell.ttl() == rowLiveness.ttl() && cell.localDeletionTime() == rowLiveness.localExpirationTime(); if (!useRowTimestamp) size += header.timestampSerializedSize(cell.timestamp()); if ((isDeleted || isExpiring) && !useRowTTL) size += header.localDeletionTimeSerializedSize(cell.localDeletionTime()); if (isExpiring && !useRowTTL) size += header.ttlSerializedSize(cell.ttl()); if (column.isComplex()) size += column.cellPathSerializer().serializedSize(cell.path()); if (hasValue) size += header.getType(column).writtenLength(cell.value()); return size; } // Returns if the skipped cell was an actual cell (i.e. it had its presence flag). public boolean skip(DataInputPlus in, ColumnMetadata column, SerializationHeader header) throws IOException { int flags = in.readUnsignedByte(); boolean hasValue = (flags & HAS_EMPTY_VALUE_MASK) == 0; boolean isDeleted = (flags & IS_DELETED_MASK) != 0; boolean isExpiring = (flags & IS_EXPIRING_MASK) != 0; boolean useRowTimestamp = (flags & USE_ROW_TIMESTAMP_MASK) != 0; boolean useRowTTL = (flags & USE_ROW_TTL_MASK) != 0; if (!useRowTimestamp) header.skipTimestamp(in); if (!useRowTTL && (isDeleted || isExpiring)) header.skipLocalDeletionTime(in); if (!useRowTTL && isExpiring) header.skipTTL(in); if (column.isComplex()) column.cellPathSerializer().skip(in); if (hasValue) header.getType(column).skipValue(in); return true; } } }