org.apache.hadoop.hbase.regionserver.querymatcher

类 ExplicitColumnTracker

java.lang.Object

org.apache.hadoop.hbase.regionserver.querymatcher.ExplicitColumnTracker

所有已实现的接口:

ColumnTracker

@InterfaceAudience.Private
public class ExplicitColumnTracker
extends Object
implements ColumnTracker

This class is used for the tracking and enforcement of columns and numbers of versions during the course of a Get or Scan operation, when explicit column qualifiers have been asked for in the query. With a little magic (see ScanQueryMatcher), we can use this matcher for both scans and gets. The main difference is 'next' and 'done' collapse for the scan case (since we see all columns in order), and we only reset between rows.

This class is utilized by ScanQueryMatcher mainly through two methods:

• checkColumn(byte[], int, int, byte) is called when a Put satisfies all other conditions of the query.
• getNextRowOrNextColumn(byte[], int, int) is called whenever ScanQueryMatcher believes that the current column should be skipped (by timestamp, filter etc.)

These two methods returns a ScanQueryMatcher.MatchCode to define what action should be taken.

This class is NOT thread-safe as queries are never multi-threaded

构造器概要

构造器

构造器和说明
ExplicitColumnTracker(NavigableSet<byte[]> columns, int minVersions, int maxVersions, long oldestUnexpiredTS) Default constructor.

方法概要

方法

限定符和类型	方法和说明
ScanQueryMatcher.MatchCode	checkColumn(byte[] bytes, int offset, int length, byte type) Checks if the column is present in the list of requested columns by returning the match code instance.
ScanQueryMatcher.MatchCode	checkVersions(byte[] bytes, int offset, int length, long timestamp, byte type, boolean ignoreCount) Keeps track of the number of versions for the columns asked for.
boolean	done() Done when there are no more columns to match against.
void	doneWithColumn(byte[] bytes, int offset, int length) This method is used to inform the column tracker that we are done with this column.
org.apache.hadoop.hbase.regionserver.querymatcher.ColumnCount	getColumnHint() Used by matcher and scan/get to get a hint of the next column to seek to after checkColumn() returns SKIP.
ScanQueryMatcher.MatchCode	getNextRowOrNextColumn(byte[] bytes, int offset, int qualLength) Retrieve the MatchCode for the next row or column
boolean	isDone(long timestamp) Give the tracker a chance to declare it's done based on only the timestamp to allow an early out.
void	reset() Resets the Matcher

从类继承的方法 java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

构造器详细资料

ExplicitColumnTracker

public ExplicitColumnTracker(NavigableSet<byte[]> columns,
                     int minVersions,
                     int maxVersions,
                     long oldestUnexpiredTS)

Default constructor.

参数:

columns - columns specified user in query

minVersions - minimum number of versions to keep

maxVersions - maximum versions to return per column

oldestUnexpiredTS - the oldest timestamp we are interested in, based on TTL

方法详细资料

done

public boolean done()

Done when there are no more columns to match against.

指定者:

done 在接口中 ColumnTracker

返回:

true when done.

getColumnHint

public org.apache.hadoop.hbase.regionserver.querymatcher.ColumnCount getColumnHint()

从接口复制的说明: ColumnTracker

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.

指定者:

getColumnHint 在接口中 ColumnTracker

返回:

null, or a ColumnCount that we should seek to

checkColumn

public ScanQueryMatcher.MatchCode checkColumn(byte[] bytes,
                                     int offset,
                                     int length,
                                     byte type)

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 ColumnTracker.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 ScanQueryMatcher.MatchCode.INCLUDE, ScanQueryMatcher.MatchCode.SEEK_NEXT_COL and ScanQueryMatcher.MatchCode.SEEK_NEXT_ROW.

指定者:

checkColumn 在接口中 ColumnTracker

type - The type of the KeyValue

返回:

The match code instance.

checkVersions

public ScanQueryMatcher.MatchCode checkVersions(byte[] bytes,
                                       int offset,
                                       int length,
                                       long timestamp,
                                       byte type,
                                       boolean ignoreCount)
                                         throws IOException

从接口复制的说明: ColumnTracker

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 ColumnTracker.checkColumn(byte[], int, int, byte) method. The enum values returned by this method are ScanQueryMatcher.MatchCode.SKIP, ScanQueryMatcher.MatchCode.INCLUDE, ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_COL and ScanQueryMatcher.MatchCode.INCLUDE_AND_SEEK_NEXT_ROW. Implementations which include all the columns could just return ScanQueryMatcher.MatchCode.INCLUDE in the ColumnTracker.checkColumn(byte[], int, int, byte) method and perform all the operations in this checkVersions method.

指定者:

checkVersions 在接口中 ColumnTracker

timestamp - The timeToLive to enforce.

type - the type of the key value (Put/Delete)

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.)

返回:

the scan query matcher match code instance

抛出:

IOException - in case there is an internal consistency problem caused by a data corruption.

reset

public void reset()

从接口复制的说明: ColumnTracker

Resets the Matcher

指定者:

reset 在接口中 ColumnTracker

doneWithColumn

public void doneWithColumn(byte[] bytes,
                  int offset,
                  int length)

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 required only in case of ExplicitColumnTracker.

参数:

bytes -

offset -

length -

getNextRowOrNextColumn

public ScanQueryMatcher.MatchCode getNextRowOrNextColumn(byte[] bytes,
                                                int offset,
                                                int qualLength)

从接口复制的说明: ColumnTracker

Retrieve the MatchCode for the next row or column

指定者:

getNextRowOrNextColumn 在接口中 ColumnTracker

isDone

public boolean isDone(long timestamp)

从接口复制的说明: ColumnTracker

Give the tracker a chance to declare it's done based on only the timestamp to allow an early out.

指定者:

isDone 在接口中 ColumnTracker

返回:

true to early out based on timestamp.