HFileBlockIndex.BlockIndexReader (Apache HBase 1.4.11 API)

java.lang.Object
- org.apache.hadoop.hbase.io.hfile.HFileBlockIndex.BlockIndexReader

All Implemented Interfaces:

HeapSize

Enclosing class:

HFileBlockIndex
```
public static class HFileBlockIndex.BlockIndexReader
extends Object
implements HeapSize
```
The reader will always hold the root level index in the memory. Index blocks at all other levels will be cached in the LRU cache in practice, although this API does not enforce that.
All non-root (leaf and intermediate) index blocks contain what we call a "secondary index": an array of offsets to the entries within the block. This allows us to do binary search for the entry corresponding to the given key without having to deserialize the block.

Constructor Summary

Constructors
Constructor and Description
`HFileBlockIndex.BlockIndexReader(KeyValue.KVComparator c, int treeLevel)`
`HFileBlockIndex.BlockIndexReader(KeyValue.KVComparator c, int treeLevel, HFile.CachingBlockReader cachingBlockReader)`

Method Summary

Methods
Modifier and Type	Method and Description
`void`	`ensureNonEmpty()` Verifies that the block index is non-empty and throws an `IllegalStateException` otherwise.
`int`	`getRootBlockCount()`
`int`	`getRootBlockDataSize(int i)`
`byte[]`	`getRootBlockKey(int i)`
`long`	`getRootBlockOffset(int i)`
`long`	`heapSize()`
`boolean`	`isEmpty()`
`BlockWithScanInfo`	`loadDataBlockWithScanInfo(Cell key, HFileBlock currentBlock, boolean cacheBlocks, boolean pread, boolean isCompaction, DataBlockEncoding expectedDataBlockEncoding)` Return the BlockWithScanInfo, a data structure which contains the Data HFileBlock with other scan info such as the key that starts the next HFileBlock.
`byte[]`	`midkey()` An approximation to the `HFile`'s mid-key.
`void`	`readMultiLevelIndexRoot(HFileBlock blk, int numEntries)` Read the root-level metadata of a multi-level block index.
`void`	`readRootIndex(DataInput in, int numEntries)` Read in the root-level index from the given input stream.
`DataInputStream`	`readRootIndex(HFileBlock blk, int numEntries)` Read in the root-level index from the given input stream.
`int`	`rootBlockContainingKey(byte[] key, int offset, int length)` Finds the root-level index block containing the given key.
`int`	`rootBlockContainingKey(Cell key)` Finds the root-level index block containing the given key.
`HFileBlock`	`seekToDataBlock(Cell key, HFileBlock currentBlock, boolean cacheBlocks, boolean pread, boolean isCompaction, DataBlockEncoding expectedDataBlockEncoding)` Return the data block which contains this key.
`String`	`toString()`

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

- Constructor Detail
  - HFileBlockIndex.BlockIndexReader
```
public HFileBlockIndex.BlockIndexReader(KeyValue.KVComparator c,
                                int treeLevel,
                                HFile.CachingBlockReader cachingBlockReader)
```
  - HFileBlockIndex.BlockIndexReader
```
public HFileBlockIndex.BlockIndexReader(KeyValue.KVComparator c,
                                int treeLevel)
```
- Method Detail
  - isEmpty
```
public boolean isEmpty()
```
    Returns:
    true if the block index is empty.
  - ensureNonEmpty
```
public void ensureNonEmpty()
```
    Verifies that the block index is non-empty and throws an IllegalStateException otherwise.
  - seekToDataBlock
```
public HFileBlock seekToDataBlock(Cell key,
                         HFileBlock currentBlock,
                         boolean cacheBlocks,
                         boolean pread,
                         boolean isCompaction,
                         DataBlockEncoding expectedDataBlockEncoding)
                           throws IOException
```
    Return the data block which contains this key. This function will only be called when the HFile version is larger than 1.
    
    Parameters:
    key - the key we are looking for
    currentBlock - the current block, to avoid re-reading the same block
    cacheBlocks -
    pread -
    isCompaction -
    expectedDataBlockEncoding - the data block encoding the caller is expecting the data block to be in, or null to not perform this check and return the block irrespective of the encoding
    
    Returns:
    reader a basic way to load blocks
    
    Throws:
    
    IOException
  - loadDataBlockWithScanInfo
```
public BlockWithScanInfo loadDataBlockWithScanInfo(Cell key,
                                          HFileBlock currentBlock,
                                          boolean cacheBlocks,
                                          boolean pread,
                                          boolean isCompaction,
                                          DataBlockEncoding expectedDataBlockEncoding)
                                            throws IOException
```
    Return the BlockWithScanInfo, a data structure which contains the Data HFileBlock with other scan info such as the key that starts the next HFileBlock. This function will only be called when the HFile version is larger than 1.
    
    Parameters:
    key - the key we are looking for
    currentBlock - the current block, to avoid re-reading the same block
    cacheBlocks -
    pread -
    isCompaction -
    expectedDataBlockEncoding - the data block encoding the caller is expecting the data block to be in, or null to not perform this check and return the block irrespective of the encoding.
    
    Returns:
    the BlockWithScanInfo which contains the DataBlock with other scan info such as nextIndexedKey.
    
    Throws:
    
    IOException
  - midkey
```
public byte[] midkey()
              throws IOException
```
    An approximation to the HFile's mid-key. Operates on block boundaries, and does not go inside blocks. In other words, returns the first key of the middle block of the file.
    
    Returns:
    the first key of the middle block
    
    Throws:
    
    IOException
  - getRootBlockKey
```
public byte[] getRootBlockKey(int i)
```
    Parameters:
    i - from 0 to - 1
  - getRootBlockOffset
```
public long getRootBlockOffset(int i)
```
    Parameters:
    i - from 0 to - 1
  - getRootBlockDataSize
```
public int getRootBlockDataSize(int i)
```
    Parameters:
    i - zero-based index of a root-level block
    
    Returns:
    the on-disk size of the root-level block for version 2, or the uncompressed size for version 1
  - getRootBlockCount
```
public int getRootBlockCount()
```
    Returns:
    the number of root-level blocks in this block index
  - rootBlockContainingKey
```
public int rootBlockContainingKey(byte[] key,
                         int offset,
                         int length)
```
    Finds the root-level index block containing the given key.
    
    Parameters:
    key - Key to find
    
    Returns:
    Offset of block containing key (between 0 and the number of blocks - 1) or -1 if this file does not contain the request.
  - rootBlockContainingKey
```
public int rootBlockContainingKey(Cell key)
```
    Finds the root-level index block containing the given key.
    
    Parameters:
    key - Key to find
  - readRootIndex
```
public void readRootIndex(DataInput in,
                 int numEntries)
                   throws IOException
```
    Read in the root-level index from the given input stream. Must match what was written into the root level by HFileBlockIndex.BlockIndexWriter.writeIndexBlocks(FSDataOutputStream) at the offset that function returned.
    
    Parameters:
    in - the buffered input stream or wrapped byte input stream
    numEntries - the number of root-level index entries
    
    Throws:
    
    IOException
  - readRootIndex
```
public DataInputStream readRootIndex(HFileBlock blk,
                            int numEntries)
                              throws IOException
```
    Read in the root-level index from the given input stream. Must match what was written into the root level by HFileBlockIndex.BlockIndexWriter.writeIndexBlocks(FSDataOutputStream) at the offset that function returned.
    
    Parameters:
    blk - the HFile block
    numEntries - the number of root-level index entries
    
    Returns:
    the buffered input stream or wrapped byte input stream
    
    Throws:
    
    IOException
  - readMultiLevelIndexRoot
```
public void readMultiLevelIndexRoot(HFileBlock blk,
                           int numEntries)
                             throws IOException
```
    Read the root-level metadata of a multi-level block index. Based on readRootIndex(DataInput, int), but also reads metadata necessary to compute the mid-key in a multi-level index.
    
    Parameters:
    blk - the HFile block
    numEntries - the number of root-level index entries
    
    Throws:
    
    IOException
  - toString
```
public String toString()
```
    Overrides:
    
    toString in class Object
  - heapSize
```
public long heapSize()
```
    Specified by:
    
    heapSize in interface HeapSize
    
    Returns:
    Approximate 'exclusive deep size' of implementing object. Includes count of payload and hosting object sizings.

Class HFileBlockIndex.BlockIndexReader

Constructor Summary

Method Summary

Methods inherited from class java.lang.Object

Constructor Detail

HFileBlockIndex.BlockIndexReader

HFileBlockIndex.BlockIndexReader

Method Detail

isEmpty

ensureNonEmpty

seekToDataBlock

loadDataBlockWithScanInfo

midkey

getRootBlockKey

getRootBlockOffset

getRootBlockDataSize

getRootBlockCount

rootBlockContainingKey

rootBlockContainingKey

readRootIndex

readRootIndex

readMultiLevelIndexRoot

toString

heapSize