org.apache.hudi.io.hfile

Interface HFileReader

All Superinterfaces:

AutoCloseable, Closeable

All Known Implementing Classes:

CachingHFileReaderImpl, HFileReaderImpl

public interface HFileReader
extends Closeable

HFile reader that supports seeks.

Field Summary

Fields

Modifier and Type	Field and Description
static int	SEEK_TO_BEFORE_BLOCK_FIRST_KEY
static int	SEEK_TO_BEFORE_FILE_FIRST_KEY
static int	SEEK_TO_EOF
static int	SEEK_TO_FOUND
static int	SEEK_TO_IN_RANGE

Method Summary

Modifier and Type	Method and Description
Option<KeyValue>	getKeyValue()
Option<ByteBuffer>	getMetaBlock(String metaBlockName) Gets the content of a meta block from HFile.
Option<byte[]>	getMetaInfo(UTF8StringKey key) Gets info entry from file info block of a HFile.
long	getNumKeyValueEntries()
void	initializeMetadata() Initializes metadata based on a HFile before other read operations.
boolean	isSeeked()
boolean	next() Scans to the next entry in the file.
boolean	seekTo() Positions this reader at the start of the file.
int	seekTo(Key key) seekTo or just before the passed Key.

Methods inherited from interface java.io.Closeable

close

Field Detail

SEEK_TO_BEFORE_BLOCK_FIRST_KEY

static final int SEEK_TO_BEFORE_BLOCK_FIRST_KEY

See Also:

Constant Field Values

SEEK_TO_BEFORE_FILE_FIRST_KEY

static final int SEEK_TO_BEFORE_FILE_FIRST_KEY

See Also:

Constant Field Values

SEEK_TO_FOUND

static final int SEEK_TO_FOUND

See Also:

Constant Field Values

SEEK_TO_IN_RANGE

static final int SEEK_TO_IN_RANGE

See Also:

Constant Field Values

SEEK_TO_EOF

static final int SEEK_TO_EOF

See Also:

Constant Field Values

Method Detail

initializeMetadata

void initializeMetadata()
                 throws IOException

Initializes metadata based on a HFile before other read operations.

Throws:

IOException - upon read errors.

getMetaInfo

Option<byte[]> getMetaInfo(UTF8StringKey key)
                    throws IOException

Gets info entry from file info block of a HFile.

Parameters:

key - meta key.

Returns:

the content in bytes if present.

Throws:

IOException - upon read errors.

getMetaBlock

Option<ByteBuffer> getMetaBlock(String metaBlockName)
                         throws IOException

Gets the content of a meta block from HFile.

Parameters:

metaBlockName - meta block name.

Returns:

the content in bytes if present.

Throws:

IOException - upon read errors.

getNumKeyValueEntries

long getNumKeyValueEntries()

Returns:

total number of key value entries in the HFile.

seekTo

int seekTo(Key key)
    throws IOException

seekTo or just before the passed Key. Examine the return code to figure whether we found the key or not. Consider the key-value pairs in the file, kv[0] .. kv[n-1], where there are n KV pairs in the file.

The position only moves forward so the caller has to make sure the keys are sorted before making multiple calls of this method.

Parameters:

key - Key to seek to.

Returns:

-2 (SEEK_TO_BEFORE_BLOCK_FIRST_KEY), such that block_fake_first_key <= key < block_actual_first_key if there is no exact match, and the reader is left in position at block_actual_first_key; -1 (SEEK_TO_BEFORE_FILE_FIRST_KEY), if key < kv[0], the reader is left in position 0; 0 (SEEK_TO_FOUND), such that kv[i].key = key and the reader is left in position i; 1 (SEEK_TO_IN_RANGE), such that kv[i].key < key if there is no exact match and the key is greater than the actual first of the data block, and the reader is left in position i; 2 (SEEK_TO_EOF), if there is no KV greater than or equal to the input key, and the reader positions itself at the end of the file and next() will return false when it is called.

Throws:

IOException - upon read errors.

seekTo

boolean seekTo()
        throws IOException

Positions this reader at the start of the file.

Returns:

false if empty file; i.e. a call to next would return false and the current key and value are undefined.

Throws:

IOException - upon read errors.

next

boolean next()
      throws IOException

Scans to the next entry in the file.

Returns:

false if the current position is at the end; otherwise true if more in file.

Throws:

IOException - upon read errors.

getKeyValue

Option<KeyValue> getKeyValue()
                      throws IOException

Returns:

The KeyValue instance at current position.

Throws:

IOException

isSeeked

boolean isSeeked()

Returns:

true if the reader has had one of the seek calls invoked; i.e. seekTo() or seekTo(Key). Otherwise, false.