org.apache.hadoop.hbase

Interface Cell

All Superinterfaces:

HeapSize

All Known Subinterfaces:

ExtendedCell, RawCell

All Known Implementing Classes:

BufferedDataBlockEncoder.OffheapDecodedExtendedCell, BufferedDataBlockEncoder.OnheapDecodedCell, ByteBufferChunkKeyValue, ByteBufferExtendedCell, ByteBufferKeyOnlyKeyValue, ByteBufferKeyValue, IndividualBytesFieldCell, KeyOnlyFilter.KeyOnlyByteBufferExtendedCell, KeyOnlyFilter.KeyOnlyCell, KeyValue, KeyValue.KeyOnlyKeyValue, MapReduceExtendedCell, Mutation.CellWrapper, NoTagByteBufferChunkKeyValue, NoTagsByteBufferKeyValue, NoTagsKeyValue, PrivateCellUtil.EmptyByteBufferExtendedCell, PrivateCellUtil.EmptyCell, PrivateCellUtil.FirstOnRowByteBufferExtendedCell, PrivateCellUtil.FirstOnRowCell, PrivateCellUtil.FirstOnRowColByteBufferExtendedCell, PrivateCellUtil.FirstOnRowColCell, PrivateCellUtil.FirstOnRowColTSByteBufferExtendedCell, PrivateCellUtil.FirstOnRowColTSCell, PrivateCellUtil.FirstOnRowDeleteFamilyCell, PrivateCellUtil.LastOnRowByteBufferExtendedCell, PrivateCellUtil.LastOnRowCell, PrivateCellUtil.LastOnRowColByteBufferExtendedCell, PrivateCellUtil.LastOnRowColCell, PrivateCellUtil.TagRewriteByteBufferExtendedCell, PrivateCellUtil.TagRewriteCell, PrivateCellUtil.ValueAndTagRewriteByteBufferExtendedCell, PrivateCellUtil.ValueAndTagRewriteCell, SizeCachedKeyValue, SizeCachedNoTagsKeyValue

@InterfaceAudience.Public
public interface Cell
extends HeapSize

The unit of storage in HBase consisting of the following fields:

 1) row
 2) column family
 3) column qualifier
 4) timestamp
 5) type
 6) MVCC version
 7) value
 

Uniqueness is determined by the combination of row, column family, column qualifier, timestamp, and type.

The natural comparator will perform a bitwise comparison on row, column family, and column qualifier. Less intuitively, it will then treat the greater timestamp as the lesser value with the goal of sorting newer cells first.

Cell implements Comparable<Cell> which is only meaningful when comparing to other keys in the same table. It uses CellComparator which does not work on the -ROOT- and hbase:meta tables.

In the future, we may consider adding a boolean isOnHeap() method and a getValueBuffer() method that can be used to pass a value directly from an off-heap ByteBuffer to the network without copying into an on-heap byte[].

Historic note: the original Cell implementation (KeyValue) requires that all fields be encoded as consecutive bytes in the same byte[], whereas this interface allows fields to reside in separate byte[]'s.

Nested Class Summary

Nested Classes

Modifier and Type	Interface and Description
static class	Cell.Type The valid types for user to build the cell.

Method Summary

Modifier and Type	Method and Description
byte[]	getFamilyArray() Contiguous bytes composed of legal HDFS filename characters which may start at any index in the containing array.
byte	getFamilyLength()
int	getFamilyOffset()
byte[]	getQualifierArray() Contiguous raw bytes that may start at any index in the containing array.
int	getQualifierLength()
int	getQualifierOffset()
byte[]	getRowArray() Contiguous raw bytes that may start at any index in the containing array.
short	getRowLength()
int	getRowOffset()
long	getSequenceId() Deprecated. As of HBase-2.0. Will be removed in HBase-3.0.
int	getSerializedSize()
byte[]	getTagsArray() Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Tags are are now internal.
int	getTagsLength() Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Tags are are now internal.
int	getTagsOffset() Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Tags are are now internal.
long	getTimestamp()
default Cell.Type	getType() Returns the type of cell in a human readable format using Cell.Type.
byte	getTypeByte() Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Use getType().
byte[]	getValueArray() Contiguous raw bytes that may start at any index in the containing array.
int	getValueLength()
int	getValueOffset()

Methods inherited from interface org.apache.hadoop.hbase.io.HeapSize

heapSize

Method Detail

getRowArray

byte[] getRowArray()

Contiguous raw bytes that may start at any index in the containing array. Max length is Short.MAX_VALUE which is 32,767 bytes.

Returns:

The array containing the row bytes.

getRowOffset

int getRowOffset()

Returns:

Array index of first row byte

getRowLength

short getRowLength()

Returns:

Number of row bytes. Must be < rowArray.length - offset.

getFamilyArray

byte[] getFamilyArray()

Contiguous bytes composed of legal HDFS filename characters which may start at any index in the containing array. Max length is Byte.MAX_VALUE, which is 127 bytes.

Returns:

the array containing the family bytes.

getFamilyOffset

int getFamilyOffset()

Returns:

Array index of first family byte

getFamilyLength

byte getFamilyLength()

Returns:

Number of family bytes. Must be < familyArray.length - offset.

getQualifierArray

byte[] getQualifierArray()

Contiguous raw bytes that may start at any index in the containing array.

Returns:

The array containing the qualifier bytes.

getQualifierOffset

int getQualifierOffset()

Returns:

Array index of first qualifier byte

getQualifierLength

int getQualifierLength()

Returns:

Number of qualifier bytes. Must be < qualifierArray.length - offset.

getTimestamp

long getTimestamp()

Returns:

Long value representing time at which this cell was "Put" into the row. Typically represents the time of insertion, but can be any value from 0 to Long.MAX_VALUE.

getTypeByte

@Deprecated
byte getTypeByte()

Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Use getType().

Returns:

The byte representation of the KeyValue.TYPE of this cell: one of Put, Delete, etc

getSequenceId

@Deprecated
long getSequenceId()

Deprecated. As of HBase-2.0. Will be removed in HBase-3.0.

A region-specific unique monotonically increasing sequence ID given to each Cell. It always exists for cells in the memstore but is not retained forever. It will be kept for HConstants.KEEP_SEQID_PERIOD days, but generally becomes irrelevant after the cell's row is no longer involved in any operations that require strict consistency.

Returns:

seqId (always > 0 if exists), or 0 if it no longer exists

getValueArray

byte[] getValueArray()

Contiguous raw bytes that may start at any index in the containing array. Max length is Integer.MAX_VALUE which is 2,147,483,647 bytes.

Returns:

The array containing the value bytes.

getValueOffset

int getValueOffset()

Returns:

Array index of first value byte

getValueLength

int getValueLength()

Returns:

Number of value bytes. Must be < valueArray.length - offset.

getSerializedSize

int getSerializedSize()

Returns:

Serialized size (defaults to include tag length if has some tags).

getTagsArray

@Deprecated
byte[] getTagsArray()

Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Tags are are now internal.

Contiguous raw bytes representing tags that may start at any index in the containing array.

Returns:

the tags byte array

getTagsOffset

@Deprecated
int getTagsOffset()

Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Tags are are now internal.

Returns:

the first offset where the tags start in the Cell

getTagsLength

@Deprecated
int getTagsLength()

Deprecated. As of HBase-2.0. Will be removed in HBase-3.0. Tags are are now internal.

HBase internally uses 2 bytes to store tags length in Cell. As the tags length is always a non-negative number, to make good use of the sign bit, the max of tags length is defined 2 * Short.MAX_VALUE + 1 = 65535. As a result, the return type is int, because a short is not capable of handling that. Please note that even if the return type is int, the max tags length is far less than Integer.MAX_VALUE.

Returns:

the total length of the tags in the Cell.

getType

default Cell.Type getType()

Returns the type of cell in a human readable format using Cell.Type. Note : This does not expose the internal types of Cells like KeyValue.Type.Maximum and KeyValue.Type.Minimum

Returns:

The data type this cell: one of Put, Delete, etc