org.apache.pig.backend.datastorage

Interface ElementDescriptor

All Superinterfaces:

Comparable<ElementDescriptor>

All Known Subinterfaces:

ContainerDescriptor

All Known Implementing Classes:

HDirectory, HFile, HPath

public interface ElementDescriptor
extends Comparable<ElementDescriptor>

DataStorageElementDescriptor provides methods necessary to manage an element in a DataStorage.

Field Summary

Fields

Modifier and Type	Field and Description
static String	BLOCK_REPLICATION_KEY Available from getConfiguration as a String and getStatistics as a Short.
static String	BLOCK_SIZE_KEY Available from getConfiguration as a String and getStatistics as a Long.
static String	LENGTH_KEY Available from getStatistics as a Long.
static String	MODIFICATION_TIME_KEY Available from getStatistics as a Long.

Method Summary

Modifier and Type	Method and Description
void	copy(ElementDescriptor dstName, boolean removeSrc)
void	copy(ElementDescriptor dstName, Properties dstConfiguration, boolean removeSrc) Copy entity from an existing one, possibly residing in a different Data Storage.
OutputStream	create()
OutputStream	create(Properties configuration) Opens a stream onto which an entity can be written to.
void	delete() Remove entity from the Data Storage.
boolean	exists() Checks whether the entity exists or not
Properties	getConfiguration() Retrieve configuration information for entity
DataStorage	getDataStorage()
Map<String,Object>	getStatistics() List entity statistics
InputStream	open()
InputStream	open(Properties configuration) Open for read a given entity
void	rename(ElementDescriptor newName) Changes the name of an entity in the Data Storage
SeekableInputStream	sopen()
SeekableInputStream	sopen(Properties configuration) Open an element in the Data Storage with support for random access (seek operations).
boolean	systemElement() Defines whether the element is visible to users or contains system's metadata
void	updateConfiguration(Properties newConfig) Update configuration information for this entity

Methods inherited from interface java.lang.Comparable

compareTo

Field Detail

BLOCK_SIZE_KEY

static final String BLOCK_SIZE_KEY

Available from getConfiguration as a String and getStatistics as a Long.

See Also:

Constant Field Values

BLOCK_REPLICATION_KEY

static final String BLOCK_REPLICATION_KEY

Available from getConfiguration as a String and getStatistics as a Short.

See Also:

Constant Field Values

LENGTH_KEY

static final String LENGTH_KEY

Available from getStatistics as a Long.

See Also:

Constant Field Values

MODIFICATION_TIME_KEY

static final String MODIFICATION_TIME_KEY

Available from getStatistics as a Long.

See Also:

Constant Field Values

Method Detail

getDataStorage

DataStorage getDataStorage()

create

OutputStream create(Properties configuration)
             throws IOException

Opens a stream onto which an entity can be written to.

Parameters:

configuration - information at the object level

Returns:

stream where to write

Throws:

DataStorageException

IOException

create

OutputStream create()
             throws IOException

Throws:

IOException

copy

void copy(ElementDescriptor dstName,
          Properties dstConfiguration,
          boolean removeSrc)
   throws IOException

Copy entity from an existing one, possibly residing in a different Data Storage.

Parameters:

dstName - name of entity to create

dstConfiguration - configuration for the new entity

removeSrc - if src entity needs to be removed after copying it

Throws:

DataStorageException - for instance, configuration information for new entity is not compatible with configuration information at the Data Storage level, user does not have privileges to read from source entity or write to destination storage...

IOException

copy

void copy(ElementDescriptor dstName,
          boolean removeSrc)
   throws IOException

Throws:

IOException

open

InputStream open(Properties configuration)
          throws IOException

Open for read a given entity

Parameters:

configuration -

Returns:

entity to read from

Throws:

DataStorageExecption - e.g. entity does not exist...

IOException

open

InputStream open()
          throws IOException

Throws:

IOException

sopen

SeekableInputStream sopen(Properties configuration)
                   throws IOException

Open an element in the Data Storage with support for random access (seek operations).

Parameters:

configuration -

Returns:

a seekable input stream

Throws:

DataStorageException

IOException

sopen

SeekableInputStream sopen()
                   throws IOException

Throws:

IOException

exists

boolean exists()
        throws IOException

Checks whether the entity exists or not

Returns:

true if entity exists, false otherwise.

Throws:

IOException

rename

void rename(ElementDescriptor newName)
     throws IOException

Changes the name of an entity in the Data Storage

Parameters:

newName - new name of entity

Throws:

DataStorageException

IOException

delete

void delete()
     throws IOException

Remove entity from the Data Storage.

Throws:

DataStorageException

IOException

getConfiguration

Properties getConfiguration()
                     throws IOException

Retrieve configuration information for entity

Returns:

configuration

Throws:

IOException

updateConfiguration

void updateConfiguration(Properties newConfig)
                  throws IOException

Update configuration information for this entity

Parameters:

newConfig - configuration

Throws:

DataStorageException

IOException

systemElement

boolean systemElement()

Defines whether the element is visible to users or contains system's metadata

Returns:

true if this is system file; false otherwise

getStatistics

Map<String,Object> getStatistics()
                          throws IOException

List entity statistics

Returns:

DataStorageProperties

Throws:

IOException