001/*
002 * Licensed to the Apache Software Foundation (ASF) under one
003 * or more contributor license agreements.  See the NOTICE file
004 * distributed with this work for additional information
005 * regarding copyright ownership.  The ASF licenses this file
006 * to you under the Apache License, Version 2.0 (the
007 * "License"); you may not use this file except in compliance
008 * with the License.  You may obtain a copy of the License at
009 *
010 *     http://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package org.apache.hadoop.hbase.regionserver.querymatcher;
019
020import java.io.IOException;
021import org.apache.hadoop.hbase.Cell;
022import org.apache.hadoop.hbase.regionserver.ShipperListener;
023import org.apache.hadoop.hbase.regionserver.querymatcher.ScanQueryMatcher.MatchCode;
024import org.apache.yetus.audience.InterfaceAudience;
025
026/**
027 * Implementing classes of this interface will be used for the tracking and enforcement of columns
028 * and numbers of versions and timeToLive during the course of a Get or Scan operation.
029 * <p>
030 * Currently there are two different types of Store/Family-level queries.
031 * <ul>
032 * <li>{@link ExplicitColumnTracker} is used when the query specifies one or more column qualifiers
033 * to return in the family.</li>
034 * <li>{@link ScanWildcardColumnTracker} is used when no columns are explicitly specified.</li>
035 * </ul>
036 * <p>
037 * This class is utilized by {@link ScanQueryMatcher} mainly through two methods:
038 * <ul>
039 * <li>{@link #checkColumn} is called when a Put satisfies all other conditions of the query.</li>
040 * <li>{@link #getNextRowOrNextColumn} is called whenever ScanQueryMatcher believes that the current
041 * column should be skipped (by timestamp, filter etc.)</li>
042 * </ul>
043 * <p>
044 * These two methods returns a
045 * {@link org.apache.hadoop.hbase.regionserver.querymatcher.ScanQueryMatcher.MatchCode} to define
046 * what action should be taken.
047 * <p>
048 * This class is NOT thread-safe as queries are never multi-threaded
049 */
050@InterfaceAudience.Private
051public interface ColumnTracker extends ShipperListener {
052
053  /**
054   * Checks if the column is present in the list of requested columns by returning the match code
055   * instance. It does not check against the number of versions for the columns asked for. To do the
056   * version check, one has to call {@link #checkVersions(Cell, long, byte, boolean)} method based
057   * on the return type (INCLUDE) of this method. The values that can be returned by this method are
058   * {@link MatchCode#INCLUDE}, {@link MatchCode#SEEK_NEXT_COL} and {@link MatchCode#SEEK_NEXT_ROW}.
059   * @param cell a cell with the column to match against
060   * @param type The type of the Cell
061   * @return The match code instance.
062   * @throws IOException in case there is an internal consistency problem caused by a data
063   *                     corruption.
064   */
065  ScanQueryMatcher.MatchCode checkColumn(Cell cell, byte type) throws IOException;
066
067  /**
068   * Keeps track of the number of versions for the columns asked for. It assumes that the user has
069   * already checked if the cell needs to be included by calling the
070   * {@link #checkColumn(Cell, byte)} method. The enum values returned by this method are
071   * {@link MatchCode#SKIP}, {@link MatchCode#INCLUDE}, {@link MatchCode#INCLUDE_AND_SEEK_NEXT_COL}
072   * and {@link MatchCode#INCLUDE_AND_SEEK_NEXT_ROW}. Implementations which include all the columns
073   * could just return {@link MatchCode#INCLUDE} in the {@link #checkColumn(Cell, byte)} method and
074   * perform all the operations in this checkVersions method.
075   * @param cell        a cell with the column to match against
076   * @param timestamp   The timestamp of the cell.
077   * @param type        the type of the key value (Put/Delete)
078   * @param ignoreCount indicates if the KV needs to be excluded while counting (used during
079   *                    compactions. We only count KV's that are older than all the scanners' read
080   *                    points.)
081   * @return the scan query matcher match code instance
082   * @throws IOException in case there is an internal consistency problem caused by a data
083   *                     corruption.
084   */
085  ScanQueryMatcher.MatchCode checkVersions(Cell cell, long timestamp, byte type,
086    boolean ignoreCount) throws IOException;
087
088  /**
089   * Resets the Matcher
090   */
091  void reset();
092
093  /** Returns <code>true</code> when done. */
094  boolean done();
095
096  /**
097   * Used by matcher and scan/get to get a hint of the next column to seek to after checkColumn()
098   * returns SKIP. Returns the next interesting column we want, or NULL there is none (wildcard
099   * scanner). Implementations aren't required to return anything useful unless the most recent call
100   * was to checkColumn() and the return code was SKIP. This is pretty implementation detail-y, but
101   * optimizations are like that.
102   * @return null, or a ColumnCount that we should seek to
103   */
104  ColumnCount getColumnHint();
105
106  /**
107   * Retrieve the MatchCode for the next row or column
108   */
109  MatchCode getNextRowOrNextColumn(Cell cell);
110
111  /**
112   * Give the tracker a chance to declare it's done based on only the timestamp to allow an early
113   * out.
114   * @return <code>true</code> to early out based on timestamp.
115   */
116  boolean isDone(long timestamp);
117
118  /**
119   * This method is used to inform the column tracker that we are done with this column. We may get
120   * this information from external filters or timestamp range and we then need to indicate this
121   * information to tracker. It is currently implemented for ExplicitColumnTracker.
122   */
123  default void doneWithColumn(Cell cell) {
124  }
125}