org.apache.hadoop.hbase
Class HColumnDescriptor

java.lang.Object
  org.apache.hadoop.hbase.HColumnDescriptor

All Implemented Interfaces:

Comparable, Writable, WritableComparable

public class HColumnDescriptor
extends Object
implements WritableComparable

An HColumnDescriptor contains information about a column family such as the number of versions, compression settings, etc. It is used as input when creating a table or adding a column. Once set, the parameters that specify a column cannot be changed without deleting the column and recreating it. If there is data stored in the column, it will be deleted when the column is deleted.

Nested Class Summary

static class

HColumnDescriptor.CompressionType The type of compression.

Field Summary

static BloomFilterDescriptor	DEFAULT_BLOOM_FILTER_DESCRIPTOR Default bloom filter description.
static HColumnDescriptor.CompressionType	DEFAULT_COMPRESSION_TYPE Default compression type.
static boolean	DEFAULT_IN_MEMORY Default setting for whether to serve from memory or not.
static int	DEFAULT_MAX_VALUE_LENGTH Default maximum length of cell contents.
static int	DEFAULT_N_VERSIONS Default number of versions of a record to keep.
static Pattern	LEGAL_FAMILY_NAME Legal family names can only contain 'word characters' and end in a colon.

Constructor Summary

HColumnDescriptor()
Default constructor.

HColumnDescriptor(String columnName)
Construct a column descriptor specifying only the family name The other attributes are defaulted.

HColumnDescriptor(Text name, int maxVersions, HColumnDescriptor.CompressionType compression, boolean inMemory, int maxValueLength, BloomFilterDescriptor bloomFilter)
Constructor Specify all parameters.

Method Summary

int	compareTo(Object o)
boolean	equals(Object obj)
BloomFilterDescriptor	getBloomFilter()
HColumnDescriptor.CompressionType	getCompression()
HColumnDescriptor.CompressionType	getCompressionType()
Text	getFamilyName()
int	getMaxValueLength()
int	getMaxVersions()
Text	getName()
int	hashCode()
boolean	isInMemory()
void	readFields(DataInput in) Deserialize the fields of this object from in.
String	toString()
void	write(DataOutput out) Serialize the fields of this object to out.

Methods inherited from class java.lang.Object

clone, finalize, getClass, notify, notifyAll, wait, wait, wait

Field Detail

LEGAL_FAMILY_NAME

public static final Pattern LEGAL_FAMILY_NAME

Legal family names can only contain 'word characters' and end in a colon.

DEFAULT_COMPRESSION_TYPE

public static final HColumnDescriptor.CompressionType DEFAULT_COMPRESSION_TYPE

Default compression type.

DEFAULT_N_VERSIONS

public static final int DEFAULT_N_VERSIONS

Default number of versions of a record to keep.

See Also:

Constant Field Values

DEFAULT_IN_MEMORY

public static final boolean DEFAULT_IN_MEMORY

Default setting for whether to serve from memory or not.

See Also:

Constant Field Values

DEFAULT_MAX_VALUE_LENGTH

public static final int DEFAULT_MAX_VALUE_LENGTH

Default maximum length of cell contents.

See Also:

Constant Field Values

DEFAULT_BLOOM_FILTER_DESCRIPTOR

public static final BloomFilterDescriptor DEFAULT_BLOOM_FILTER_DESCRIPTOR

Default bloom filter description.

Constructor Detail

HColumnDescriptor

public HColumnDescriptor()

Default constructor. Must be present for Writable.

HColumnDescriptor

public HColumnDescriptor(String columnName)

Construct a column descriptor specifying only the family name The other attributes are defaulted.

Parameters:

columnName - - column family name

HColumnDescriptor

public HColumnDescriptor(Text name,
                         int maxVersions,
                         HColumnDescriptor.CompressionType compression,
                         boolean inMemory,
                         int maxValueLength,
                         BloomFilterDescriptor bloomFilter)

Constructor Specify all parameters.

Parameters:

name - Column family name

maxVersions - Maximum number of versions to keep

compression - Compression type

inMemory - If true, column data should be kept in an HRegionServer's cache

maxValueLength - Restrict values to <= this value

bloomFilter - Enable the specified bloom filter for this column

Throws:

IllegalArgumentException - if passed a family name that is made of other than 'word' characters: i.e. [a-zA-Z_0-9] and does not end in a :

IllegalArgumentException - if the number of versions is <= 0

Method Detail

getName

public Text getName()

Returns:

name of column family

getFamilyName

public Text getFamilyName()

Returns:

name of column family without trailing ':'

getCompression

public HColumnDescriptor.CompressionType getCompression()

Returns:

compression type being used for the column family

getMaxVersions

public int getMaxVersions()

Returns:

maximum number of versions

getCompressionType

public HColumnDescriptor.CompressionType getCompressionType()

Returns:

Compression type setting.

isInMemory

public boolean isInMemory()

Returns:

True if we are to keep all in use HRegionServer cache.

getMaxValueLength

public int getMaxValueLength()

Returns:

Maximum value length.

getBloomFilter

public BloomFilterDescriptor getBloomFilter()

Returns:

Bloom filter descriptor or null if none set.

toString

public String toString()

Overrides:

toString in class Object

equals

public boolean equals(Object obj)

Overrides:

equals in class Object

hashCode

public int hashCode()

Overrides:

hashCode in class Object

readFields

public void readFields(DataInput in)
                throws IOException

Deserialize the fields of this object from in.

For efficiency, implementations should attempt to re-use storage in the existing object where possible.

Specified by:

readFields in interface Writable

Parameters:

in - DataInput to deseriablize this object from.

Throws:

IOException

write

public void write(DataOutput out)
           throws IOException

Serialize the fields of this object to out.

Specified by:

write in interface Writable

Parameters:

out - DataOuput to serialize this object into.

Throws:

IOException

compareTo

public int compareTo(Object o)

Specified by:

compareTo in interface Comparable