org.apache.hadoop.hbase.io.hfile

Interface HFileBlock.FSReader

All Known Implementing Classes:

HFileBlock.FSReaderImpl

Enclosing class:

HFileBlock

static interface HFileBlock.FSReader

An HFile block reader with iteration ability.

Method Summary

Modifier and Type	Method and Description
HFileBlock.BlockIterator	blockRange(long startOffset, long endOffset) Creates a block iterator over the given portion of the HFile.
void	closeStreams() Closes the backing streams
HFileBlockDecodingContext	getBlockDecodingContext() Get a decoder for BlockType.ENCODED_DATA blocks from this file.
HFileBlockDecodingContext	getDefaultBlockDecodingContext() Get the default decoder for blocks from this file.
HFileBlock	readBlockData(long offset, long onDiskSize, boolean pread, boolean updateMetrics, boolean intoHeap) Reads the block at the given offset in the file with the given on-disk size and uncompressed size.
void	setDataBlockEncoder(HFileDataBlockEncoder encoder)
void	setIncludesMemStoreTS(boolean includesMemstoreTS)
void	unbufferStream() To close the stream's socket.

Method Detail

readBlockData

HFileBlock readBlockData(long offset,
                         long onDiskSize,
                         boolean pread,
                         boolean updateMetrics,
                         boolean intoHeap)
                  throws IOException

Reads the block at the given offset in the file with the given on-disk size and uncompressed size.

Parameters:

offset - of the file to read

onDiskSize - the on-disk size of the entire block, including all applicable headers, or -1 if unknown

pread - true to use pread, otherwise use the stream read.

updateMetrics - update the metrics or not.

intoHeap - allocate the block's ByteBuff by ByteBuffAllocator or JVM heap. For LRUBlockCache, we must ensure that the block to cache is an heap one, because the memory occupation is based on heap now, also for CombinedBlockCache, we use the heap LRUBlockCache as L1 cache to cache small blocks such as IndexBlock or MetaBlock for faster access. So introduce an flag here to decide whether allocate from JVM heap or not so that we can avoid an extra off-heap to heap memory copy when using LRUBlockCache. For most cases, we known what's the expected block type we'll read, while for some special case (Example: HFileReaderImpl#readNextDataBlock()), we cannot pre-decide what's the expected block type, then we can only allocate block's ByteBuff from ByteBuffAllocator firstly, and then when caching it in LruBlockCache we'll check whether the ByteBuff is from heap or not, if not then we'll clone it to an heap one and cache it.

Returns:

the newly read block

Throws:

IOException

blockRange

HFileBlock.BlockIterator blockRange(long startOffset,
                                    long endOffset)

Creates a block iterator over the given portion of the HFile. The iterator returns blocks starting with offset such that offset <= startOffset < endOffset. Returned blocks are always unpacked. Used when no hfile index available; e.g. reading in the hfile index blocks themselves on file open.

Parameters:

startOffset - the offset of the block to start iteration with

endOffset - the offset to end iteration at (exclusive)

Returns:

an iterator of blocks between the two given offsets

closeStreams

void closeStreams()
           throws IOException

Closes the backing streams

Throws:

IOException

getBlockDecodingContext

HFileBlockDecodingContext getBlockDecodingContext()

Get a decoder for BlockType.ENCODED_DATA blocks from this file.

getDefaultBlockDecodingContext

HFileBlockDecodingContext getDefaultBlockDecodingContext()

Get the default decoder for blocks from this file.

setIncludesMemStoreTS

void setIncludesMemStoreTS(boolean includesMemstoreTS)

setDataBlockEncoder

void setDataBlockEncoder(HFileDataBlockEncoder encoder)

unbufferStream

void unbufferStream()

To close the stream's socket. Note: This can be concurrently called from multiple threads and implementation should take care of thread safety.