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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
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* 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.querymatcher;
import java.io.IOException;
import org.apache.hadoop.hbase.Cell;
import org.apache.hadoop.hbase.regionserver.ShipperListener;
import org.apache.hadoop.hbase.regionserver.querymatcher.ScanQueryMatcher.MatchCode;
import org.apache.yetus.audience.InterfaceAudience;
/**
* 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.querymatcher.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 extends ShipperListener {
/**
* 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(Cell, 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 cell a cell with the column to match against
* @param type The type of the Cell
* @return The match code instance.
* @throws IOException in case there is an internal consistency problem caused by a data
* corruption.
*/
ScanQueryMatcher.MatchCode checkColumn(Cell cell, 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 cell needs to be included by calling the
* {@link #checkColumn(Cell, 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(Cell, byte)} method and
* perform all the operations in this checkVersions method.
* @param cell a cell with the column to match against
* @param timestamp The timestamp of the cell.
* @param type the type of the key value (Put/Delete)
* @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(Cell cell, long timestamp, byte type,
boolean ignoreCount) throws IOException;
/**
* Resets the Matcher
*/
void reset();
/** Returns 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(Cell cell);
/**
* Give the tracker a chance to declare it's done based on only the timestamp to allow an early
* out.
* @return true to early out based on timestamp.
*/
boolean isDone(long timestamp);
/**
* This method is used to inform the column tracker that we are done with this column. We may get
* this information from external filters or timestamp range and we then need to indicate this
* information to tracker. It is currently implemented for ExplicitColumnTracker.
*/
default void doneWithColumn(Cell cell) {
}
}