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.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. 34 * <ul><li>{@link ScanWildcardColumnTracker} is used when no columns are 35 * explicitly specified. 36 * <p> 37 * This class is utilized by {@link ScanQueryMatcher} mainly through two methods: 38 * <ul><li>{@link #checkColumn} is called when a Put satisfies all other 39 * conditions of the query. 40 * <ul><li>{@link #getNextRowOrNextColumn} is called whenever ScanQueryMatcher 41 * believes that the current column should be skipped (by timestamp, filter etc.) 42 * <p> 43 * These two methods returns a 44 * {@link org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode} 45 * to define what action should be taken. 46 * <p> 47 * This class is NOT thread-safe as queries are never multi-threaded 48 */ 49 @InterfaceAudience.Private 50 public interface ColumnTracker { 51 /** 52 * Keeps track of the number of versions for the columns asked for 53 * @param bytes 54 * @param offset 55 * @param length 56 * @param ttl The timeToLive to enforce. 57 * @param type The type of the KeyValue 58 * @param ignoreCount indicates if the KV needs to be excluded while counting 59 * (used during compactions. We only count KV's that are older than all the 60 * scanners' read points.) 61 * @return The match code instance. 62 * @throws IOException in case there is an internal consistency problem 63 * caused by a data corruption. 64 */ 65 public ScanQueryMatcher.MatchCode checkColumn(byte[] bytes, int offset, 66 int length, long ttl, byte type, boolean ignoreCount) 67 throws IOException; 68 69 /** 70 * Resets the Matcher 71 */ 72 public void reset(); 73 74 /** 75 * 76 * @return <code>true</code> when done. 77 */ 78 public boolean done(); 79 80 /** 81 * Used by matcher and scan/get to get a hint of the next column 82 * to seek to after checkColumn() returns SKIP. Returns the next interesting 83 * column we want, or NULL there is none (wildcard scanner). 84 * 85 * Implementations aren't required to return anything useful unless the most recent 86 * call was to checkColumn() and the return code was SKIP. This is pretty implementation 87 * detail-y, but optimizations are like that. 88 * 89 * @return null, or a ColumnCount that we should seek to 90 */ 91 public ColumnCount getColumnHint(); 92 93 /** 94 * Retrieve the MatchCode for the next row or column 95 */ 96 public MatchCode getNextRowOrNextColumn(byte[] bytes, int offset, 97 int qualLength); 98 99 /** 100 * Give the tracker a chance to declare it's done based on only the timestamp 101 * to allow an early out. 102 * 103 * @param timestamp 104 * @return <code>true</code> to early out based on timestamp. 105 */ 106 public boolean isDone(long timestamp); 107 }