hbase-server/src/main/java/org/apache/hadoop/hbase/regionserver/InternalScanner.java

   1 /**
   2  *
   3  * Licensed to the Apache Software Foundation (ASF) under one
   4  * or more contributor license agreements.  See the NOTICE file
   5  * distributed with this work for additional information
   6  * regarding copyright ownership.  The ASF licenses this file
   7  * to you under the Apache License, Version 2.0 (the
   8  * "License"); you may not use this file except in compliance
   9  * with the License.  You may obtain a copy of the License at
  10  *
  11  *     http://www.apache.org/licenses/LICENSE-2.0
  12  *
  13  * Unless required by applicable law or agreed to in writing, software
  14  * distributed under the License is distributed on an "AS IS" BASIS,
  15  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  16  * See the License for the specific language governing permissions and
  17  * limitations under the License.
  18  */
  19 package org.apache.hadoop.hbase.regionserver;
  20
  21 import java.io.Closeable;
  22 import java.io.IOException;
  23 import java.util.List;
  24
  25 import org.apache.hadoop.hbase.Cell;
  26 import org.apache.hadoop.hbase.HBaseInterfaceAudience;
  27 import org.apache.yetus.audience.InterfaceAudience;
  28 import org.apache.yetus.audience.InterfaceStability;
  29
  30 /**
  31  * Internal scanners differ from client-side scanners in that they operate on
  32  * HStoreKeys and byte[] instead of RowResults. This is because they are
  33  * actually close to how the data is physically stored, and therefore it is more
  34  * convenient to interact with them that way. It is also much easier to merge
  35  * the results across SortedMaps than RowResults.
  36  *
  37  * <p>Additionally, we need to be able to determine if the scanner is doing
  38  * wildcard column matches (when only a column family is specified or if a
  39  * column regex is specified) or if multiple members of the same column family
  40  * were specified. If so, we need to ignore the timestamp to ensure that we get
  41  * all the family members, as they may have been last updated at different
  42  * times.
  43  */
  44 @InterfaceAudience.LimitedPrivate(HBaseInterfaceAudience.COPROC)
  45 @InterfaceStability.Evolving
  46 public interface InternalScanner extends Closeable {
  47   /**
  48    * Grab the next row's worth of values.
  49    * @param result return output array
  50    * @return true if more rows exist after this one, false if scanner is done
  51    * @throws IOException e
  52    */
  53   default boolean next(List<Cell> result) throws IOException {
  54     return next(result, NoLimitScannerContext.getInstance());
  55   }
  56
  57   /**
  58    * Grab the next row's worth of values.
  59    * @param result return output array
  60    * @param scannerContext
  61    * @return true if more rows exist after this one, false if scanner is done
  62    * @throws IOException e
  63    */
  64   boolean next(List<Cell> result, ScannerContext scannerContext) throws IOException;
  65
  66   /**
  67    * Closes the scanner and releases any resources it has allocated
  68    * @throws IOException
  69    */
  70   @Override
  71   void close() throws IOException;
  72 }