HFileReaderImpl.HFileScannerImpl (Apache HBase

java.lang.Object
- org.apache.hadoop.hbase.io.hfile.HFileReaderImpl.HFileScannerImpl

All Implemented Interfaces:

Closeable, AutoCloseable, HFileScanner, Shipper

Direct Known Subclasses:

HFileReaderImpl.EncodedScanner

Enclosing class:

HFileReaderImpl
```
protected static class HFileReaderImpl.HFileScannerImpl
extends Object
implements HFileScanner
```

Field Summary

Fields
Modifier and Type	Field and Description
`protected boolean`	`cacheBlocks`
`protected HFileBlock`	`curBlock`
`protected boolean`	`isCompaction`
`protected Cell`	`nextIndexedKey` The next indexed key is to keep track of the indexed key of the next data block.
`protected boolean`	`pread`
`protected ArrayList<HFileBlock>`	`prevBlocks`
`protected HFile.Reader`	`reader`

Constructor Summary

Constructors
Constructor and Description

HFileScannerImpl(HFile.Reader reader, boolean cacheBlocks, boolean pread, boolean isCompaction)

Constructors
Constructor and Description
`HFileScannerImpl(HFile.Reader reader, boolean cacheBlocks, boolean pread, boolean isCompaction)`

Method Summary

All Methods Instance Methods Concrete Methods
Modifier and Type	Method and Description
`protected void`	`assertSeeked()`
`protected int`	`blockSeek(Cell key, boolean seekBefore)` Within a loaded block, seek looking for the last key that is smaller than (or equal to?) the key we are interested in.
`protected boolean`	`checkKeyLen(int v)` Returns True if v <= 0 or v > current block buffer limit.
`protected void`	`checkKeyValueLen()` Check key and value lengths are wholesome.
`protected boolean`	`checkLen(int v)` Returns True if v < 0 or v > current block buffer limit.
`void`	`close()` Close this HFile scanner and do necessary cleanup.
`int`	`compareKey(CellComparator comparator, Cell key)`
`Cell`	`getCell()` Returns Instance of `Cell`.
`DataBlockEncoding`	`getEffectiveDataBlockEncoding()`
`protected Cell`	`getFirstKeyCellInBlock(HFileBlock curBlock)`
`Cell`	`getKey()` Gets the current key in the form of a cell.
`String`	`getKeyString()` Convenience method to get a copy of the key as a string - interpreting the bytes as UTF8.
`Cell`	`getNextIndexedKey()` Returns the next key in the index (the key to seek to the next block)
`HFile.Reader`	`getReader()` Returns Reader that underlies this Scanner instance.
`ByteBuffer`	`getValue()` Gets a buffer view to the current value.
`String`	`getValueString()` Convenience method to get a copy of the value as a string - interpreting the bytes as UTF8.
`boolean`	`isSeeked()`
`protected int`	`loadBlockAndSeekToKey(HFileBlock seekToBlock, Cell nextIndexedKey, boolean rewind, Cell key, boolean seekBefore)`
`boolean`	`next()` Go to the next key/value in the block section.
`protected boolean`	`processFirstDataBlock()`
`protected void`	`readAndUpdateNewBlock(long firstDataBlockOffset)`
`protected void`	`readKeyValueLen()`
`protected void`	`readMvccVersion(int offsetFromPos)` Read mvcc.
`protected HFileBlock`	`readNextDataBlock()` Scans blocks in the "scanned" section of the `HFile` until the next data block is found.
`protected void`	`releaseIfNotCurBlock(HFileBlock block)` The curBlock will be released by shipping or close method, so only need to consider releasing the block, which was read from HFile before and not referenced by curBlock.
`int`	`reseekTo(Cell key)` Reseek to or just before the passed `cell`.
`boolean`	`seekBefore(Cell key)` Consider the cell stream of all the cells in the file, `c[0] ..`
`boolean`	`seekTo()` Positions this scanner at the start of the file.
`int`	`seekTo(Cell key)` SeekTo or just before the passed `cell`.
`int`	`seekTo(Cell key, boolean rewind)` An internal API function.
`protected void`	`setNonSeekedState()`
`void`	`shipped()` Called after a batch of rows scanned and set to be returned to client.
`String`	`toString()`
`protected void`	`updateCurrentBlock(HFileBlock newBlock)` Updates the current block to be the given `HFileBlock`.

Methods inherited from class java.lang.Object
clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

- Field Detail
  - cacheBlocks
```
protected final boolean cacheBlocks
```
  - pread
```
protected final boolean pread
```
  - isCompaction
```
protected final boolean isCompaction
```
  - reader
```
protected final HFile.Reader reader
```
  - nextIndexedKey
```
protected Cell nextIndexedKey
```
    The next indexed key is to keep track of the indexed key of the next data block. If the nextIndexedKey is HConstants.NO_NEXT_INDEXED_KEY, it means that the current data block is the last data block. If the nextIndexedKey is null, it means the nextIndexedKey has not been loaded yet.
  - curBlock
```
protected HFileBlock curBlock
```
  - prevBlocks
```
protected final ArrayList<HFileBlock> prevBlocks
```
- Constructor Detail
  - HFileScannerImpl
```
public HFileScannerImpl(HFile.Reader reader,
                        boolean cacheBlocks,
                        boolean pread,
                        boolean isCompaction)
```
- Method Detail
  - isSeeked
```
public boolean isSeeked()
```
    Specified by:
    
    isSeeked in interface HFileScanner
    
    Returns:
    
    True is scanner has had one of the seek calls invoked; i.e. HFileScanner.seekBefore(Cell) or HFileScanner.seekTo() or HFileScanner.seekTo(Cell). Otherwise returns false.
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - assertSeeked
```
protected void assertSeeked()
```
  - getReader
```
public HFile.Reader getReader()
```
    Description copied from interface: HFileScanner
    
    Returns Reader that underlies this Scanner instance.
    
    Specified by:
    
    getReader in interface HFileScanner
  - close
```
public void close()
```
    Description copied from interface: HFileScanner
    
    Close this HFile scanner and do necessary cleanup.
    
    Specified by:
    
    close in interface Closeable
    
    Specified by:
    
    close in interface AutoCloseable
    
    Specified by:
    
    close in interface HFileScanner
  - readKeyValueLen
```
protected void readKeyValueLen()
```
  - readMvccVersion
```
protected void readMvccVersion(int offsetFromPos)
```
    Read mvcc. Does checks to see if we even need to read the mvcc at all.
  - blockSeek
```
protected int blockSeek(Cell key,
                        boolean seekBefore)
```
    Within a loaded block, seek looking for the last key that is smaller than (or equal to?) the key we are interested in. A note on the seekBefore: if you have seekBefore = true, AND the first key in the block = key, then you'll get thrown exceptions. The caller has to check for that case and load the previous block as appropriate. the key to find find the key before the given key in case of exact match.
    
    Returns:
    
    0 in case of an exact key match, 1 in case of an inexact match, -2 in case of an inexact match and furthermore, the input key less than the first key of current block(e.g. using a faked index key)
  - getNextIndexedKey
```
public Cell getNextIndexedKey()
```
    Description copied from interface: HFileScanner
    
    Returns the next key in the index (the key to seek to the next block)
    
    Specified by:
    
    getNextIndexedKey in interface HFileScanner
  - seekTo
```
public int seekTo(Cell key)
           throws IOException
```
    Description copied from interface: HFileScanner
    
    SeekTo or just before the passed cell. Examine the return code to figure whether we found the cell or not. Consider the cell stream of all the cells in the file, c[0] .. c[n], where there are n cells in the file.
    
    Specified by:
    
    seekTo in interface HFileScanner
    
    Returns:
    
    -1, if cell < c[0], no position; 0, such that c[i] = cell and scanner is left in position i; and 1, such that c[i] < cell, and scanner is left in position i. The scanner will position itself between c[i] and c[i+1] where c[i] < cell <= c[i+1]. If there is no cell c[i+1] greater than or equal to the input cell, then the scanner will position itself at the end of the file and next() will return false when it is called.
    
    Throws:
    
    IOException
  - reseekTo
```
public int reseekTo(Cell key)
             throws IOException
```
    Description copied from interface: HFileScanner
    
    Reseek to or just before the passed cell. Similar to seekTo except that this can be called even if the scanner is not at the beginning of a file. This can be used to seek only to cells which come after the current position of the scanner. Consider the cell stream of all the cells in the file, c[0] .. c[n], where there are n cellc in the file after current position of HFileScanner. The scanner will position itself between c[i] and c[i+1] where c[i] < cell <= c[i+1]. If there is no cell c[i+1] greater than or equal to the input cell, then the scanner will position itself at the end of the file and next() will return false when it is called.
    
    Specified by:
    
    reseekTo in interface HFileScanner
    
    Parameters:
    
    key - Cell to find (should be non-null)
    
    Returns:
    
    -1, if cell < c[0], no position; 0, such that c[i] = cell and scanner is left in position i; and 1, such that c[i] < cell, and scanner is left in position i.
    
    Throws:
    
    IOException
  - seekTo
```
public int seekTo(Cell key,
                  boolean rewind)
           throws IOException
```
    An internal API function. Seek to the given key, optionally rewinding to the first key of the block before doing the seek.
    
    Parameters:
    
    key - - a cell representing the key that we need to fetch
    
    rewind - whether to rewind to the first key of the block before doing the seek. If this is false, we are assuming we never go back, otherwise the result is undefined.
    
    Returns:
    
    -1 if the key is earlier than the first key of the file, 0 if we are at the given key, 1 if we are past the given key -2 if the key is earlier than the first key of the file while using a faked index key
    
    Throws:
    
    IOException
  - seekBefore
```
public boolean seekBefore(Cell key)
                   throws IOException
```
    Description copied from interface: HFileScanner
    
    Consider the cell stream of all the cells in the file, c[0] .. c[n], where there are n cells in the file.
    
    Specified by:
    
    seekBefore in interface HFileScanner
    
    Parameters:
    
    key - Cell to find
    
    Returns:
    
    false if cell <= c[0] or true with scanner in position 'i' such that: c[i] < cell. Furthermore: there may be a c[i+1], such that c[i] < cell <= c[i+1] but there may also NOT be a c[i+1], and next() will return false (EOF).
    
    Throws:
    
    IOException
  - releaseIfNotCurBlock
```
protected void releaseIfNotCurBlock(HFileBlock block)
```
    The curBlock will be released by shipping or close method, so only need to consider releasing the block, which was read from HFile before and not referenced by curBlock.
  - readNextDataBlock
```
protected HFileBlock readNextDataBlock()
                                throws IOException
```
    Scans blocks in the "scanned" section of the HFile until the next data block is found.
    
    Returns:
    
    the next block, or null if there are no more data blocks
    
    Throws:
    
    IOException
  - getEffectiveDataBlockEncoding
```
public DataBlockEncoding getEffectiveDataBlockEncoding()
```
  - getCell
```
public Cell getCell()
```
    Description copied from interface: HFileScanner
    
    Returns Instance of Cell.
    
    Specified by:
    
    getCell in interface HFileScanner
  - getKey
```
public Cell getKey()
```
    Description copied from interface: HFileScanner
    
    Gets the current key in the form of a cell. You must call HFileScanner.seekTo(Cell) before this method.
    
    Specified by:
    
    getKey in interface HFileScanner
    
    Returns:
    
    gets the current key as a Cell.
  - getValue
```
public ByteBuffer getValue()
```
    Description copied from interface: HFileScanner
    
    Gets a buffer view to the current value. You must call HFileScanner.seekTo(Cell) before this method.
    
    Specified by:
    
    getValue in interface HFileScanner
    
    Returns:
    
    byte buffer for the value. The limit is set to the value size, and the position is 0, the start of the buffer view.
  - setNonSeekedState
```
protected void setNonSeekedState()
```
  - next
```
public boolean next()
             throws IOException
```
    Go to the next key/value in the block section. Loads the next block if necessary. If successful, getKey() and getValue() can be called.
    
    Specified by:
    
    next in interface HFileScanner
    
    Returns:
    
    true if successfully navigated to the next key/value
    
    Throws:
    
    IOException
  - seekTo
```
public boolean seekTo()
               throws IOException
```
    Positions this scanner at the start of the file.
    
    Specified by:
    
    seekTo in interface HFileScanner
    
    Returns:
    
    false if empty file; i.e. a call to next would return false and the current key and value are undefined.
    
    Throws:
    
    IOException
  - processFirstDataBlock
```
protected boolean processFirstDataBlock()
                                 throws IOException
```
    Throws:
    
    IOException
  - readAndUpdateNewBlock
```
protected void readAndUpdateNewBlock(long firstDataBlockOffset)
                              throws IOException
```
    Throws:
    
    IOException
  - loadBlockAndSeekToKey
```
protected int loadBlockAndSeekToKey(HFileBlock seekToBlock,
                                    Cell nextIndexedKey,
                                    boolean rewind,
                                    Cell key,
                                    boolean seekBefore)
                             throws IOException
```
    Throws:
    
    IOException
  - checkKeyLen
```
protected final boolean checkKeyLen(int v)
```
    Returns True if v <= 0 or v > current block buffer limit.
  - checkLen
```
protected final boolean checkLen(int v)
```
    Returns True if v < 0 or v > current block buffer limit.
  - checkKeyValueLen
```
protected final void checkKeyValueLen()
```
    Check key and value lengths are wholesome.
  - updateCurrentBlock
```
protected void updateCurrentBlock(HFileBlock newBlock)
                           throws IOException
```
    Updates the current block to be the given HFileBlock. Seeks to the the first key/value pair.
    
    Parameters:
    
    newBlock - the block read by HFileReaderImpl.readBlock(long, long, boolean, boolean, boolean, boolean, org.apache.hadoop.hbase.io.hfile.BlockType, org.apache.hadoop.hbase.io.encoding.DataBlockEncoding), it's a totally new block with new allocated ByteBuff, so if no further reference to this block, we should release it carefully.
    
    Throws:
    
    IOException
  - getFirstKeyCellInBlock
```
protected Cell getFirstKeyCellInBlock(HFileBlock curBlock)
```
  - getKeyString
```
public String getKeyString()
```
    Description copied from interface: HFileScanner
    
    Convenience method to get a copy of the key as a string - interpreting the bytes as UTF8. You must call HFileScanner.seekTo(Cell) before this method.
    
    Specified by:
    
    getKeyString in interface HFileScanner
    
    Returns:
    
    key as a string
  - getValueString
```
public String getValueString()
```
    Description copied from interface: HFileScanner
    
    Convenience method to get a copy of the value as a string - interpreting the bytes as UTF8. You must call HFileScanner.seekTo(Cell) before this method.
    
    Specified by:
    
    getValueString in interface HFileScanner
    
    Returns:
    
    value as a string
  - compareKey
```
public int compareKey(CellComparator comparator,
                      Cell key)
```
  - shipped
```
public void shipped()
             throws IOException
```
    Description copied from interface: Shipper
    
    Called after a batch of rows scanned and set to be returned to client. Any in between cleanup can be done here.
    
    Specified by:
    
    shipped in interface Shipper
    
    Throws:
    
    IOException

Class HFileReaderImpl.HFileScannerImpl

Field Summary

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Field Detail

cacheBlocks

pread

isCompaction

reader

nextIndexedKey

curBlock

prevBlocks

Constructor Detail

HFileScannerImpl

Method Detail

isSeeked

toString

assertSeeked

getReader

close

readKeyValueLen

readMvccVersion

blockSeek

getNextIndexedKey

seekTo

reseekTo

seekTo

seekBefore

releaseIfNotCurBlock

readNextDataBlock

getEffectiveDataBlockEncoding

getCell

getKey

getValue

setNonSeekedState

next

seekTo

processFirstDataBlock

readAndUpdateNewBlock

loadBlockAndSeekToKey

checkKeyLen

checkLen

checkKeyValueLen

updateCurrentBlock

getFirstKeyCellInBlock

getKeyString

getValueString

compareKey

shipped