1 /** 2 * Copyright 2009 The Apache Software Foundation 3 * 4 * Licensed to the Apache Software Foundation (ASF) under one 5 * or more contributor license agreements. See the NOTICE file 6 * distributed with this work for additional information 7 * regarding copyright ownership. The ASF licenses this file 8 * to you under the Apache License, Version 2.0 (the 9 * "License"); you may not use this file except in compliance 10 * with the License. You may obtain a copy of the License at 11 * 12 * http://www.apache.org/licenses/LICENSE-2.0 13 * 14 * Unless required by applicable law or agreed to in writing, software 15 * distributed under the License is distributed on an "AS IS" BASIS, 16 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 17 * See the License for the specific language governing permissions and 18 * limitations under the License. 19 */ 20 package org.apache.hadoop.hbase.regionserver; 21 22 import java.io.IOException; 23 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 * <p> 35 * This class is utilized by {@link ScanQueryMatcher} through two methods: 36 * <ul><li>{@link #checkColumn} is called when a Put satisfies all other 37 * conditions of the query. This method returns a {@link org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode} to define 38 * what action should be taken. 39 * <li>{@link #update} is called at the end of every StoreFile or memstore. 40 * <p> 41 * This class is NOT thread-safe as queries are never multi-threaded 42 */ 43 public interface ColumnTracker { 44 /** 45 * Keeps track of the number of versions for the columns asked for 46 * @param bytes 47 * @param offset 48 * @param length 49 * @param ttl The timeToLive to enforce. 50 * @param type The type of the KeyValue 51 * @param ignoreCount indicates if the KV needs to be excluded while counting 52 * (used during compactions. We only count KV's that are older than all the 53 * scanners' read points.) 54 * @return The match code instance. 55 * @throws IOException in case there is an internal consistency problem 56 * caused by a data corruption. 57 */ 58 public ScanQueryMatcher.MatchCode checkColumn(byte[] bytes, int offset, 59 int length, long ttl, byte type, boolean ignoreCount) 60 throws IOException; 61 62 /** 63 * Updates internal variables in between files 64 */ 65 public void update(); 66 67 /** 68 * Resets the Matcher 69 */ 70 public void reset(); 71 72 /** 73 * 74 * @return <code>true</code> when done. 75 */ 76 public boolean done(); 77 78 /** 79 * Used by matcher and scan/get to get a hint of the next column 80 * to seek to after checkColumn() returns SKIP. Returns the next interesting 81 * column we want, or NULL there is none (wildcard scanner). 82 * 83 * Implementations aren't required to return anything useful unless the most recent 84 * call was to checkColumn() and the return code was SKIP. This is pretty implementation 85 * detail-y, but optimizations are like that. 86 * 87 * @return null, or a ColumnCount that we should seek to 88 */ 89 public ColumnCount getColumnHint(); 90 91 /** 92 * Retrieve the MatchCode for the next row or column 93 */ 94 public MatchCode getNextRowOrNextColumn(byte[] bytes, int offset, 95 int qualLength); 96 97 /** 98 * Give the tracker a chance to declare it's done based on only the timestamp 99 * to allow an early out. 100 * 101 * @param timestamp 102 * @return <code>true</code> to early out based on timestamp. 103 */ 104 public boolean isDone(long timestamp); 105 }