1 /** 2 * 3 * Licensed to the Apache Software Foundation (ASF) under one 4 * or more contributor license agreements. See the NOTICE file 5 * distributed with this work for additional information 6 * regarding copyright ownership. The ASF licenses this file 7 * to you under the Apache License, Version 2.0 (the 8 * "License"); you may not use this file except in compliance 9 * with the License. You may obtain a copy of the License at 10 * 11 * http://www.apache.org/licenses/LICENSE-2.0 12 * 13 * Unless required by applicable law or agreed to in writing, software 14 * distributed under the License is distributed on an "AS IS" BASIS, 15 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 16 * See the License for the specific language governing permissions and 17 * limitations under the License. 18 */ 19 package org.apache.hadoop.hbase.regionserver; 20 21 import java.io.IOException; 22 23 import org.apache.hadoop.hbase.classification.InterfaceAudience; 24 import org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode; 25 26 /** 27 * Implementing classes of this interface will be used for the tracking 28 * and enforcement of columns and numbers of versions and timeToLive during 29 * the course of a Get or Scan operation. 30 * <p> 31 * Currently there are two different types of Store/Family-level queries. 32 * <ul><li>{@link ExplicitColumnTracker} is used when the query specifies 33 * one or more column qualifiers to return in the family.</li> 34 * <li>{@link ScanWildcardColumnTracker} is used when no columns are 35 * explicitly specified.</li> 36 * </ul> 37 * <p> 38 * This class is utilized by {@link ScanQueryMatcher} mainly through two methods: 39 * <ul><li>{@link #checkColumn} is called when a Put satisfies all other 40 * conditions of the query.</li> 41 * <li>{@link #getNextRowOrNextColumn} is called whenever ScanQueryMatcher 42 * believes that the current column should be skipped (by timestamp, filter etc.)</li> 43 * </ul> 44 * <p> 45 * These two methods returns a 46 * {@link org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode} 47 * to define what action should be taken. 48 * <p> 49 * This class is NOT thread-safe as queries are never multi-threaded 50 */ 51 @InterfaceAudience.Private 52 public interface ColumnTracker { 53 54 /** 55 * Checks if the column is present in the list of requested columns by returning the match code 56 * instance. It does not check against the number of versions for the columns asked for. To do the 57 * version check, one has to call {@link #checkVersions(byte[], int, int, long, byte, boolean)} 58 * method based on the return type (INCLUDE) of this method. The values that can be returned by 59 * this method are {@link MatchCode#INCLUDE}, {@link MatchCode#SEEK_NEXT_COL} and 60 * {@link MatchCode#SEEK_NEXT_ROW}. 61 * @param bytes 62 * @param offset 63 * @param length 64 * @param type The type of the KeyValue 65 * @return The match code instance. 66 * @throws IOException in case there is an internal consistency problem caused by a data 67 * corruption. 68 */ 69 ScanQueryMatcher.MatchCode checkColumn(byte[] bytes, int offset, int length, byte type) 70 throws IOException; 71 72 /** 73 * Keeps track of the number of versions for the columns asked for. It assumes that the user has 74 * already checked if the keyvalue needs to be included by calling the 75 * {@link #checkColumn(byte[], int, int, byte)} method. The enum values returned by this method 76 * are {@link MatchCode#SKIP}, {@link MatchCode#INCLUDE}, 77 * {@link MatchCode#INCLUDE_AND_SEEK_NEXT_COL} and {@link MatchCode#INCLUDE_AND_SEEK_NEXT_ROW}. 78 * Implementations which include all the columns could just return {@link MatchCode#INCLUDE} in 79 * the {@link #checkColumn(byte[], int, int, byte)} method and perform all the operations in this 80 * checkVersions method. 81 * @param type the type of the key value (Put/Delete) 82 * @param ttl The timeToLive to enforce. 83 * @param ignoreCount indicates if the KV needs to be excluded while counting (used during 84 * compactions. We only count KV's that are older than all the scanners' read points.) 85 * @return the scan query matcher match code instance 86 * @throws IOException in case there is an internal consistency problem caused by a data 87 * corruption. 88 */ 89 ScanQueryMatcher.MatchCode checkVersions(byte[] bytes, int offset, int length, long ttl, 90 byte type, boolean ignoreCount) throws IOException; 91 /** 92 * Resets the Matcher 93 */ 94 void reset(); 95 96 /** 97 * 98 * @return <code>true</code> when done. 99 */ 100 boolean done(); 101 102 /** 103 * Used by matcher and scan/get to get a hint of the next column 104 * to seek to after checkColumn() returns SKIP. Returns the next interesting 105 * column we want, or NULL there is none (wildcard scanner). 106 * 107 * Implementations aren't required to return anything useful unless the most recent 108 * call was to checkColumn() and the return code was SKIP. This is pretty implementation 109 * detail-y, but optimizations are like that. 110 * 111 * @return null, or a ColumnCount that we should seek to 112 */ 113 ColumnCount getColumnHint(); 114 115 /** 116 * Retrieve the MatchCode for the next row or column 117 */ 118 MatchCode getNextRowOrNextColumn( 119 byte[] bytes, int offset, int qualLength 120 ); 121 122 /** 123 * Give the tracker a chance to declare it's done based on only the timestamp 124 * to allow an early out. 125 * 126 * @param timestamp 127 * @return <code>true</code> to early out based on timestamp. 128 */ 129 boolean isDone(long timestamp); 130 }