org.apache.hadoop.hbase.regionserver

Class StoreFileScanner

java.lang.Object

org.apache.hadoop.hbase.regionserver.StoreFileScanner

All Implemented Interfaces:

KeyValueScanner

@InterfaceAudience.LimitedPrivate(value="Coprocessor")
public class StoreFileScanner
extends Object
implements KeyValueScanner

KeyValueScanner adaptor over the Reader. It also provides hooks into bloom filter things.

Constructor Summary

Constructors

Constructor and Description
StoreFileScanner(StoreFile.Reader reader, HFileScanner hfs, boolean useMVCC, boolean hasMVCC, long readPt) Implements a KeyValueScanner on top of the specified HFileScanner

Method Summary

Methods

Modifier and Type	Method and Description
boolean	backwardSeek(KeyValue key) Seek the scanner at or before the row of specified KeyValue, it firstly tries to seek the scanner at or after the specified KeyValue, return if peek KeyValue of scanner has the same row with specified KeyValue, otherwise seek the scanner at the first KeyValue of the row which is the previous row of specified KeyValue
void	close() Close the KeyValue scanner.
void	enforceSeek() Does the real seek operation in case it was skipped by seekToRowCol(KeyValue, boolean) (TODO: Whats this?).
static List<StoreFileScanner>	getScannersForStoreFiles(Collection<StoreFile> files, boolean cacheBlocks, boolean usePread, boolean isCompaction, long readPt) Return an array of scanners corresponding to the given set of store files.
static List<StoreFileScanner>	getScannersForStoreFiles(Collection<StoreFile> files, boolean cacheBlocks, boolean usePread, boolean isCompaction, ScanQueryMatcher matcher, long readPt) Return an array of scanners corresponding to the given set of store files, And set the ScanQueryMatcher for each store file scanner for further optimization
static List<StoreFileScanner>	getScannersForStoreFiles(Collection<StoreFile> files, boolean cacheBlocks, boolean usePread, long readPt) Return an array of scanners corresponding to the given set of store files.
long	getSequenceID() Get the sequence id associated with this KeyValueScanner.
boolean	isFileScanner()
KeyValue	next() Return the next KeyValue in this scanner, iterating the scanner
KeyValue	peek() Look at the next KeyValue in this scanner, but do not iterate scanner.
boolean	realSeekDone() We optimize our store scanners by checking the most recent store file first, so we sometimes pretend we have done a seek but delay it until the store scanner bubbles up to the top of the key-value heap.
boolean	requestSeek(KeyValue kv, boolean forward, boolean useBloom) Pretend we have done a seek but don't do it yet, if possible.
boolean	reseek(KeyValue key) Reseek the scanner at or after the specified KeyValue.
boolean	seek(KeyValue key) Seek the scanner at or after the specified KeyValue.
static boolean	seekAtOrAfter(HFileScanner s, KeyValue k)
boolean	seekToLastRow() Seek the scanner at the first KeyValue of last row
boolean	seekToPreviousRow(KeyValue key) Seek the scanner at the first KeyValue of the row which is the previous row of specified key
void	setScanQueryMatcher(ScanQueryMatcher matcher)
boolean	shouldUseScanner(Scan scan, SortedSet<byte[]> columns, long oldestUnexpiredTS) Allows to filter out scanners (both StoreFile and memstore) that we don't want to use based on criteria such as Bloom filters and timestamp ranges.
protected boolean	skipKVsNewerThanReadpoint()
String	toString()

Methods inherited from class java.lang.Object

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

Constructor Detail

StoreFileScanner

public StoreFileScanner(StoreFile.Reader reader,
                HFileScanner hfs,
                boolean useMVCC,
                boolean hasMVCC,
                long readPt)

Implements a KeyValueScanner on top of the specified HFileScanner

Parameters:

hfs - HFile scanner

Method Detail

getScannersForStoreFiles

public static List<StoreFileScanner> getScannersForStoreFiles(Collection<StoreFile> files,
                                              boolean cacheBlocks,
                                              boolean usePread,
                                              long readPt)
                                                       throws IOException

Return an array of scanners corresponding to the given set of store files.

Throws:

IOException

getScannersForStoreFiles

public static List<StoreFileScanner> getScannersForStoreFiles(Collection<StoreFile> files,
                                              boolean cacheBlocks,
                                              boolean usePread,
                                              boolean isCompaction,
                                              long readPt)
                                                       throws IOException

Return an array of scanners corresponding to the given set of store files.

Throws:

IOException

getScannersForStoreFiles

public static List<StoreFileScanner> getScannersForStoreFiles(Collection<StoreFile> files,
                                              boolean cacheBlocks,
                                              boolean usePread,
                                              boolean isCompaction,
                                              ScanQueryMatcher matcher,
                                              long readPt)
                                                       throws IOException

Return an array of scanners corresponding to the given set of store files, And set the ScanQueryMatcher for each store file scanner for further optimization

Throws:

IOException

toString

public String toString()

Overrides:

toString in class Object

peek

public KeyValue peek()

Description copied from interface: KeyValueScanner

Look at the next KeyValue in this scanner, but do not iterate scanner.

Specified by:

peek in interface KeyValueScanner

Returns:

the next KeyValue

next

public KeyValue next()
              throws IOException

Description copied from interface: KeyValueScanner

Return the next KeyValue in this scanner, iterating the scanner

Specified by:

next in interface KeyValueScanner

Returns:

the next KeyValue

Throws:

IOException

seek

public boolean seek(KeyValue key)
             throws IOException

Description copied from interface: KeyValueScanner

Seek the scanner at or after the specified KeyValue.

Specified by:

seek in interface KeyValueScanner

Parameters:

key - seek value

Returns:

true if scanner has values left, false if end of scanner

Throws:

IOException

reseek

public boolean reseek(KeyValue key)
               throws IOException

Description copied from interface: KeyValueScanner

Reseek the scanner at or after the specified KeyValue. This method is guaranteed to seek at or after the required key only if the key comes after the current position of the scanner. Should not be used to seek to a key which may come before the current position.

Specified by:

reseek in interface KeyValueScanner

Parameters:

key - seek value (should be non-null)

Returns:

true if scanner has values left, false if end of scanner

Throws:

IOException

skipKVsNewerThanReadpoint

protected boolean skipKVsNewerThanReadpoint()
                                     throws IOException

Throws:

IOException

close

public void close()

Description copied from interface: KeyValueScanner

Close the KeyValue scanner.

Specified by:

close in interface KeyValueScanner

seekAtOrAfter

public static boolean seekAtOrAfter(HFileScanner s,
                    KeyValue k)
                             throws IOException

Parameters:

s -

k -

Returns:

false if not found or if k is after the end.

Throws:

IOException

getSequenceID

public long getSequenceID()

Description copied from interface: KeyValueScanner

Get the sequence id associated with this KeyValueScanner. This is required for comparing multiple files to find out which one has the latest data. The default implementation for this would be to return 0. A file having lower sequence id will be considered to be the older one.

Specified by:

getSequenceID in interface KeyValueScanner

requestSeek

public boolean requestSeek(KeyValue kv,
                  boolean forward,
                  boolean useBloom)
                    throws IOException

Pretend we have done a seek but don't do it yet, if possible. The hope is that we find requested columns in more recent files and won't have to seek in older files. Creates a fake key/value with the given row/column and the highest (most recent) possible timestamp we might get from this file. When users of such "lazy scanner" need to know the next KV precisely (e.g. when this scanner is at the top of the heap), they run enforceSeek().

Note that this function does guarantee that the current KV of this scanner will be advanced to at least the given KV. Because of this, it does have to do a real seek in cases when the seek timestamp is older than the highest timestamp of the file, e.g. when we are trying to seek to the next row/column and use OLDEST_TIMESTAMP in the seek key.

Specified by:

requestSeek in interface KeyValueScanner

forward - do a forward-only "reseek" instead of a random-access seek

useBloom - whether to enable multi-column Bloom filter optimization

Throws:

IOException

realSeekDone

public boolean realSeekDone()

Description copied from interface: KeyValueScanner

We optimize our store scanners by checking the most recent store file first, so we sometimes pretend we have done a seek but delay it until the store scanner bubbles up to the top of the key-value heap. This method is then used to ensure the top store file scanner has done a seek operation.

Specified by:

realSeekDone in interface KeyValueScanner

enforceSeek

public void enforceSeek()
                 throws IOException

Description copied from interface: KeyValueScanner

Does the real seek operation in case it was skipped by seekToRowCol(KeyValue, boolean) (TODO: Whats this?). Note that this function should be never called on scanners that always do real seek operations (i.e. most of the scanners). The easiest way to achieve this is to call KeyValueScanner.realSeekDone() first.

Specified by:

enforceSeek in interface KeyValueScanner

Throws:

IOException

setScanQueryMatcher

public void setScanQueryMatcher(ScanQueryMatcher matcher)

isFileScanner

public boolean isFileScanner()

Specified by:

isFileScanner in interface KeyValueScanner

Returns:

true if this is a file scanner. Otherwise a memory scanner is assumed.

shouldUseScanner

public boolean shouldUseScanner(Scan scan,
                       SortedSet<byte[]> columns,
                       long oldestUnexpiredTS)

Description copied from interface: KeyValueScanner

Allows to filter out scanners (both StoreFile and memstore) that we don't want to use based on criteria such as Bloom filters and timestamp ranges.

Specified by:

shouldUseScanner in interface KeyValueScanner

Parameters:

scan - the scan that we are selecting scanners for

columns - the set of columns in the current column family, or null if not specified by the scan

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

Returns:

true if the scanner should be included in the query

seekToPreviousRow

public boolean seekToPreviousRow(KeyValue key)
                          throws IOException

Description copied from interface: KeyValueScanner

Seek the scanner at the first KeyValue of the row which is the previous row of specified key

Specified by:

seekToPreviousRow in interface KeyValueScanner

Parameters:

key - seek value

Returns:

true if the scanner at the first valid KeyValue of previous row, false if not existing such KeyValue

Throws:

IOException

seekToLastRow

public boolean seekToLastRow()
                      throws IOException

Description copied from interface: KeyValueScanner

Seek the scanner at the first KeyValue of last row

Specified by:

seekToLastRow in interface KeyValueScanner

Returns:

true if scanner has values left, false if the underlying data is empty

Throws:

IOException

backwardSeek

public boolean backwardSeek(KeyValue key)
                     throws IOException

Description copied from interface: KeyValueScanner

Seek the scanner at or before the row of specified KeyValue, it firstly tries to seek the scanner at or after the specified KeyValue, return if peek KeyValue of scanner has the same row with specified KeyValue, otherwise seek the scanner at the first KeyValue of the row which is the previous row of specified KeyValue

Specified by:

backwardSeek in interface KeyValueScanner

Parameters:

key - seek KeyValue

Returns:

true if the scanner is at the valid KeyValue, false if such KeyValue does not exist

Throws:

IOException