001/* 002 * Licensed to the Apache Software Foundation (ASF) under one 003 * or more contributor license agreements. See the NOTICE file 004 * distributed with this work for additional information 005 * regarding copyright ownership. The ASF licenses this file 006 * to you under the Apache License, Version 2.0 (the 007 * "License"); you may not use this file except in compliance 008 * with the License. You may obtain a copy of the License at 009 * 010 * http://www.apache.org/licenses/LICENSE-2.0 011 * 012 * Unless required by applicable law or agreed to in writing, software 013 * distributed under the License is distributed on an "AS IS" BASIS, 014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 015 * See the License for the specific language governing permissions and 016 * limitations under the License. 017 */ 018package org.apache.hadoop.hbase.regionserver; 019 020import java.io.IOException; 021import java.util.List; 022import org.apache.hadoop.hbase.Cell; 023import org.apache.hadoop.hbase.HBaseInterfaceAudience; 024import org.apache.hadoop.hbase.client.RegionInfo; 025import org.apache.yetus.audience.InterfaceAudience; 026import org.apache.yetus.audience.InterfaceStability; 027 028/** 029 * RegionScanner describes iterators over rows in an HRegion. 030 */ 031@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC) 032@InterfaceStability.Evolving 033public interface RegionScanner extends InternalScanner { 034 /** Returns The RegionInfo for this scanner. */ 035 RegionInfo getRegionInfo(); 036 037 /** 038 * @return True if a filter indicates that this scanner will return no further rows. 039 * @throws IOException in case of I/O failure on a filter. 040 */ 041 boolean isFilterDone() throws IOException; 042 043 /** 044 * Do a reseek to the required row. Should not be used to seek to a key which may come before the 045 * current position. Always seeks to the beginning of a row boundary. nn * if row is null 046 */ 047 boolean reseek(byte[] row) throws IOException; 048 049 /** 050 * @return The preferred max buffersize. See 051 * {@link org.apache.hadoop.hbase.client.Scan#setMaxResultSize(long)} 052 */ 053 long getMaxResultSize(); 054 055 /** Returns The Scanner's MVCC readPt see {@link MultiVersionConcurrencyControl} */ 056 long getMvccReadPoint(); 057 058 /** 059 * @return The limit on the number of cells to retrieve on each call to next(). See 060 * {@link org.apache.hadoop.hbase.client.Scan#setBatch(int)} 061 */ 062 int getBatch(); 063 064 /** 065 * @return The Scanner's {@link org.apache.hadoop.hbase.client.Scan#ID_ATRIBUTE} value, or null if 066 * not set. 067 */ 068 default String getOperationId() { 069 return null; 070 } 071 072 /** 073 * Grab the next row's worth of values. This is a special internal method to be called from 074 * coprocessor hooks to avoid expensive setup. Caller must set the thread's readpoint, start and 075 * close a region operation, an synchronize on the scanner object. Caller should maintain and 076 * update metrics. See {@link #nextRaw(List, ScannerContext)} 077 * @param result return output array 078 * @return true if more rows exist after this one, false if scanner is done 079 * @throws IOException e 080 */ 081 boolean nextRaw(List<Cell> result) throws IOException; 082 083 /** 084 * Grab the next row's worth of values. The {@link ScannerContext} is used to enforce and track 085 * any limits associated with this call. Any progress that exists in the {@link ScannerContext} 086 * prior to calling this method will be LOST if {@link ScannerContext#getKeepProgress()} is false. 087 * Upon returning from this method, the {@link ScannerContext} will contain information about the 088 * progress made towards the limits. This is a special internal method to be called from 089 * coprocessor hooks to avoid expensive setup. Caller must set the thread's readpoint, start and 090 * close a region operation, an synchronize on the scanner object. Example: <code> 091 * HRegion region = ...; 092 * RegionScanner scanner = ... 093 * MultiVersionConcurrencyControl.setThreadReadPoint(scanner.getMvccReadPoint()); 094 * region.startRegionOperation(); 095 * try { 096 * synchronized(scanner) { 097 * ... 098 * boolean moreRows = scanner.nextRaw(values); 099 * ... 100 * } 101 * } finally { 102 * region.closeRegionOperation(); 103 * } 104 * </code> 105 * @param result return output array 106 * @param scannerContext The {@link ScannerContext} instance encapsulating all limits that should 107 * be tracked during calls to this method. The progress towards these limits 108 * can be tracked within this instance. 109 * @return true if more rows exist after this one, false if scanner is done 110 * @throws IOException e 111 */ 112 boolean nextRaw(List<Cell> result, ScannerContext scannerContext) throws IOException; 113}