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/**
*
* Licensed to the Apache Software Foundation (ASF) under one
* or more contributor license agreements. See the NOTICE file
* distributed with this work for additional information
* regarding copyright ownership. The ASF licenses this file
* to you under the Apache License, Version 2.0 (the
* "License"); you may not use this file except in compliance
* with the License. You may obtain a copy of the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*/
package org.apache.hadoop.hbase.regionserver;
import java.io.IOException;
import org.apache.hadoop.hbase.classification.InterfaceAudience;
import org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode;
/**
* Implementing classes of this interface will be used for the tracking
* and enforcement of columns and numbers of versions and timeToLive during
* the course of a Get or Scan operation.
*
* Currently there are two different types of Store/Family-level queries.
*
- {@link ExplicitColumnTracker} is used when the query specifies
* one or more column qualifiers to return in the family.
*
- {@link ScanWildcardColumnTracker} is used when no columns are
* explicitly specified.
*
* This class is utilized by {@link ScanQueryMatcher} mainly through two methods:
*
- {@link #checkColumn} is called when a Put satisfies all other
* conditions of the query.
*
- {@link #getNextRowOrNextColumn} is called whenever ScanQueryMatcher
* believes that the current column should be skipped (by timestamp, filter etc.)
*
* These two methods returns a
* {@link org.apache.hadoop.hbase.regionserver.ScanQueryMatcher.MatchCode}
* to define what action should be taken.
*
* This class is NOT thread-safe as queries are never multi-threaded
*/
@InterfaceAudience.Private
public interface ColumnTracker {
/**
* Checks if the column is present in the list of requested columns by returning the match code
* instance. It does not check against the number of versions for the columns asked for. To do the
* version check, one has to call {@link #checkVersions(byte[], int, int, long, byte, boolean)}
* method based on the return type (INCLUDE) of this method. The values that can be returned by
* this method are {@link MatchCode#INCLUDE}, {@link MatchCode#SEEK_NEXT_COL} and
* {@link MatchCode#SEEK_NEXT_ROW}.
* @param bytes
* @param offset
* @param length
* @param type The type of the KeyValue
* @return The match code instance.
* @throws IOException in case there is an internal consistency problem caused by a data
* corruption.
*/
ScanQueryMatcher.MatchCode checkColumn(byte[] bytes, int offset, int length, byte type)
throws IOException;
/**
* Keeps track of the number of versions for the columns asked for. It assumes that the user has
* already checked if the keyvalue needs to be included by calling the
* {@link #checkColumn(byte[], int, int, byte)} method. The enum values returned by this method
* are {@link MatchCode#SKIP}, {@link MatchCode#INCLUDE},
* {@link MatchCode#INCLUDE_AND_SEEK_NEXT_COL} and {@link MatchCode#INCLUDE_AND_SEEK_NEXT_ROW}.
* Implementations which include all the columns could just return {@link MatchCode#INCLUDE} in
* the {@link #checkColumn(byte[], int, int, byte)} method and perform all the operations in this
* checkVersions method.
* @param type the type of the key value (Put/Delete)
* @param ttl The timeToLive to enforce.
* @param ignoreCount indicates if the KV needs to be excluded while counting (used during
* compactions. We only count KV's that are older than all the scanners' read points.)
* @return the scan query matcher match code instance
* @throws IOException in case there is an internal consistency problem caused by a data
* corruption.
*/
ScanQueryMatcher.MatchCode checkVersions(byte[] bytes, int offset, int length, long ttl,
byte type, boolean ignoreCount) throws IOException;
/**
* Resets the Matcher
*/
void reset();
/**
*
* @return true when done.
*/
boolean done();
/**
* Used by matcher and scan/get to get a hint of the next column
* to seek to after checkColumn() returns SKIP. Returns the next interesting
* column we want, or NULL there is none (wildcard scanner).
*
* Implementations aren't required to return anything useful unless the most recent
* call was to checkColumn() and the return code was SKIP. This is pretty implementation
* detail-y, but optimizations are like that.
*
* @return null, or a ColumnCount that we should seek to
*/
ColumnCount getColumnHint();
/**
* Retrieve the MatchCode for the next row or column
*/
MatchCode getNextRowOrNextColumn(
byte[] bytes, int offset, int qualLength
);
/**
* Give the tracker a chance to declare it's done based on only the timestamp
* to allow an early out.
*
* @param timestamp
* @return true to early out based on timestamp.
*/
boolean isDone(long timestamp);
}