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 * <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 public interface ColumnTracker { 50 /** 51 * Keeps track of the number of versions for the columns asked for 52 * @param bytes 53 * @param offset 54 * @param length 55 * @param ttl The timeToLive to enforce. 56 * @param type The type of the KeyValue 57 * @param ignoreCount indicates if the KV needs to be excluded while counting 58 * (used during compactions. We only count KV's that are older than all the 59 * scanners' read points.) 60 * @return The match code instance. 61 * @throws IOException in case there is an internal consistency problem 62 * caused by a data corruption. 63 */ 64 public ScanQueryMatcher.MatchCode checkColumn(byte[] bytes, int offset, 65 int length, long ttl, byte type, boolean ignoreCount) 66 throws IOException; 67 68 /** 69 * Resets the Matcher 70 */ 71 public void reset(); 72 73 /** 74 * 75 * @return <code>true</code> when done. 76 */ 77 public boolean done(); 78 79 /** 80 * Used by matcher and scan/get to get a hint of the next column 81 * to seek to after checkColumn() returns SKIP. Returns the next interesting 82 * column we want, or NULL there is none (wildcard scanner). 83 * 84 * Implementations aren't required to return anything useful unless the most recent 85 * call was to checkColumn() and the return code was SKIP. This is pretty implementation 86 * detail-y, but optimizations are like that. 87 * 88 * @return null, or a ColumnCount that we should seek to 89 */ 90 public ColumnCount getColumnHint(); 91 92 /** 93 * Retrieve the MatchCode for the next row or column 94 */ 95 public MatchCode getNextRowOrNextColumn(byte[] bytes, int offset, 96 int qualLength); 97 98 /** 99 * Give the tracker a chance to declare it's done based on only the timestamp 100 * to allow an early out. 101 * 102 * @param timestamp 103 * @return <code>true</code> to early out based on timestamp. 104 */ 105 public boolean isDone(long timestamp); 106 }