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 /** 23 * Implementing classes of this interface will be used for the tracking 24 * and enforcement of columns and numbers of versions during the course of a 25 * Get or Scan operation. 26 * <p> 27 * Currently there are two different types of Store/Family-level queries. 28 * <ul><li>{@link ExplicitColumnTracker} is used when the query specifies 29 * one or more column qualifiers to return in the family. 30 * <p> 31 * This class is utilized by {@link ScanQueryMatcher} through two methods: 32 * <ul><li>{@link #checkColumn} is called when a Put satisfies all other 33 * conditions of the query. This method returns a {@link org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode} to define 34 * what action should be taken. 35 * <li>{@link #update} is called at the end of every StoreFile or memstore. 36 * <p> 37 * This class is NOT thread-safe as queries are never multi-threaded 38 */ 39 public interface ColumnTracker { 40 /** 41 * Keeps track of the number of versions for the columns asked for 42 * @param bytes 43 * @param offset 44 * @param length 45 * @param timestamp 46 * @return The match code instance. 47 */ 48 public ScanQueryMatcher.MatchCode checkColumn(byte [] bytes, int offset, 49 int length, long timestamp); 50 51 /** 52 * Updates internal variables in between files 53 */ 54 public void update(); 55 56 /** 57 * Resets the Matcher 58 */ 59 public void reset(); 60 61 /** 62 * 63 * @return <code>true</code> when done. 64 */ 65 public boolean done(); 66 67 /** 68 * Used by matcher and scan/get to get a hint of the next column 69 * to seek to after checkColumn() returns SKIP. Returns the next interesting 70 * column we want, or NULL there is none (wildcard scanner). 71 * 72 * Implementations aren't required to return anything useful unless the most recent 73 * call was to checkColumn() and the return code was SKIP. This is pretty implementation 74 * detail-y, but optimizations are like that. 75 * 76 * @return null, or a ColumnCount that we should seek to 77 */ 78 public ColumnCount getColumnHint(); 79 }