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.Collections;
022import java.util.List;
023import java.util.Set;
024import org.apache.hadoop.fs.Path;
025import org.apache.hadoop.hbase.ExtendedCell;
026import org.apache.hadoop.hbase.HBaseInterfaceAudience;
027import org.apache.hadoop.hbase.client.RegionInfo;
028import org.apache.yetus.audience.InterfaceAudience;
029import org.apache.yetus.audience.InterfaceStability;
030
031/**
032 * RegionScanner describes iterators over rows in an HRegion.
033 */
034@InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
035@InterfaceStability.Evolving
036public interface RegionScanner extends InternalScanner {
037  /** Returns The RegionInfo for this scanner. */
038  RegionInfo getRegionInfo();
039
040  /**
041   * @return True if a filter indicates that this scanner will return no further rows.
042   * @throws IOException in case of I/O failure on a filter.
043   */
044  boolean isFilterDone() throws IOException;
045
046  /**
047   * Do a reseek to the required row. Should not be used to seek to a key which may come before the
048   * current position. Always seeks to the beginning of a row boundary. if row is null
049   */
050  boolean reseek(byte[] row) throws IOException;
051
052  /**
053   * @return The preferred max buffersize. See
054   *         {@link org.apache.hadoop.hbase.client.Scan#setMaxResultSize(long)}
055   */
056  long getMaxResultSize();
057
058  /** Returns The Scanner's MVCC readPt see {@link MultiVersionConcurrencyControl} */
059  long getMvccReadPoint();
060
061  /**
062   * @return The limit on the number of cells to retrieve on each call to next(). See
063   *         {@link org.apache.hadoop.hbase.client.Scan#setBatch(int)}
064   */
065  int getBatch();
066
067  /**
068   * @return The Scanner's {@link org.apache.hadoop.hbase.client.Scan#ID_ATRIBUTE} value, or null if
069   *         not set.
070   */
071  default String getOperationId() {
072    return null;
073  }
074
075  /**
076   * Grab the next row's worth of values. This is a special internal method to be called from
077   * coprocessor hooks to avoid expensive setup. Caller must set the thread's readpoint, start and
078   * close a region operation, an synchronize on the scanner object. Caller should maintain and
079   * update metrics. See {@link #nextRaw(List, ScannerContext)}
080   * @param result return output array
081   * @return true if more rows exist after this one, false if scanner is done
082   * @throws IOException e
083   */
084  boolean nextRaw(List<? super ExtendedCell> result) throws IOException;
085
086  /**
087   * Grab the next row's worth of values. The {@link ScannerContext} is used to enforce and track
088   * any limits associated with this call. Any progress that exists in the {@link ScannerContext}
089   * prior to calling this method will be LOST if {@link ScannerContext#getKeepProgress()} is false.
090   * Upon returning from this method, the {@link ScannerContext} will contain information about the
091   * progress made towards the limits. This is a special internal method to be called from
092   * coprocessor hooks to avoid expensive setup. Caller must set the thread's readpoint, start and
093   * close a region operation, an synchronize on the scanner object. Example: <code>
094   * HRegion region = ...;
095   * RegionScanner scanner = ...
096   * MultiVersionConcurrencyControl.setThreadReadPoint(scanner.getMvccReadPoint());
097   * region.startRegionOperation();
098   * try {
099   *   synchronized(scanner) {
100   *     ...
101   *     boolean moreRows = scanner.nextRaw(values);
102   *     ...
103   *   }
104   * } finally {
105   *   region.closeRegionOperation();
106   * }
107   * </code>
108   * @param result         return output array
109   * @param scannerContext The {@link ScannerContext} instance encapsulating all limits that should
110   *                       be tracked during calls to this method. The progress towards these limits
111   *                       can be tracked within this instance.
112   * @return true if more rows exist after this one, false if scanner is done
113   * @throws IOException e
114   */
115  boolean nextRaw(List<? super ExtendedCell> result, ScannerContext scannerContext)
116    throws IOException;
117
118  /**
119   * Returns the set of store file paths that were successfully read by this scanner. Typically
120   * populated only after the scanner is closed.
121   */
122  default Set<Path> getFilesRead() {
123    return Collections.emptySet();
124  }
125}