src/org/apache/pig/data/package.html - pig - Git at Google

 <html>
 <body>

 <p>
 This package contains implementations of Pig specific data types as well as
 support functions for reading, writing, and using all Pig data types.
 <p>
 Whenever possible, Pig utilizes Java provided data types.  These include
 Integer, Long, Float, Double, Boolean, String, and Map.  Tuple, Bag, and
 DataByteArray are implemented in this package.

 <h2> Design </h2>
 <p>
 The choice was made to utilize Java provided types for two main reasons.  One,
 it minimizes the burden on UDF developers, as they will have full access to
 these types with no need to convert to and from Pig specific types.  Two,
 maintenance costs will be lower as there is no need to implement and maintain
 Pig specific data classes.  The drawback is that the only common parent of all
 these types is Object.  Thus Pig is often required to treat its data objects
 as Objects and then implement static methods to manipulate these Objects,
 rather than being able to define a PigDatum class with common funcitons.
 <p>
 Three data types were implemented as Pig specific classes:
 {@link org.apache.pig.data.DataByteArray}, {@link org.apache.pig.data.Tuple},
 and {@link org.apache.pig.data.DataBag}.
 <p>
 DataByteArray represents an array of bytes, with no interpretation of those
 bytes provided or assumed.  This could have been represented as byte[], but a
 separate class was constructed to provide common functions needed to
 manipulate these objects.
 <p>
 Tuple represents an ordered collection of data elements.  Every field in a
 tuple can contain any Pig data type.  Tuple is presented as an interface to
 allow differing implementations in cases where users have unique
 representations of their data that they wish to preserve in their in memory
 representations.  The {@link org.apache.pig.data.TupleFactory} is an
 abstract class, to enable a user who has defined his own tuples to provide a
 factory that creates those tuples.  Default implementations of Tuple and
 TupleFactory are provided and used by default.
 <p>
 DataBag represents a collection of Tuples.  DataBags can be of default type
 (no extra features), sorted (tuples are sorted according to a provided
 comparator function), or distinct (no duplicate tuples).  As with Tuple,
 DataBag is presented as an interface, and
 {@link org.apache.pig.data.BagFactory} is an abstract class.  Default implementations of DataBag,
 BagFactory, and all three types of bags are provided.

 </body>
 </html>
	<html>
	<body>

	<p>
	This package contains implementations of Pig specific data types as well as
	support functions for reading, writing, and using all Pig data types.
	<p>
	Whenever possible, Pig utilizes Java provided data types. These include
	Integer, Long, Float, Double, Boolean, String, and Map. Tuple, Bag, and
	DataByteArray are implemented in this package.

	<h2> Design </h2>
	<p>
	The choice was made to utilize Java provided types for two main reasons. One,
	it minimizes the burden on UDF developers, as they will have full access to
	these types with no need to convert to and from Pig specific types. Two,
	maintenance costs will be lower as there is no need to implement and maintain
	Pig specific data classes. The drawback is that the only common parent of all
	these types is Object. Thus Pig is often required to treat its data objects
	as Objects and then implement static methods to manipulate these Objects,
	rather than being able to define a PigDatum class with common funcitons.
	<p>
	Three data types were implemented as Pig specific classes:
	{@link org.apache.pig.data.DataByteArray}, {@link org.apache.pig.data.Tuple},
	and {@link org.apache.pig.data.DataBag}.
	<p>
	DataByteArray represents an array of bytes, with no interpretation of those
	bytes provided or assumed. This could have been represented as byte[], but a
	separate class was constructed to provide common functions needed to
	manipulate these objects.
	<p>
	Tuple represents an ordered collection of data elements. Every field in a
	tuple can contain any Pig data type. Tuple is presented as an interface to
	allow differing implementations in cases where users have unique
	representations of their data that they wish to preserve in their in memory
	representations. The {@link org.apache.pig.data.TupleFactory} is an
	abstract class, to enable a user who has defined his own tuples to provide a
	factory that creates those tuples. Default implementations of Tuple and
	TupleFactory are provided and used by default.
	<p>
	DataBag represents a collection of Tuples. DataBags can be of default type
	(no extra features), sorted (tuples are sorted according to a provided
	comparator function), or distinct (no duplicate tuples). As with Tuple,
	DataBag is presented as an interface, and
	{@link org.apache.pig.data.BagFactory} is an abstract class. Default implementations of DataBag,
	BagFactory, and all three types of bags are provided.

	</body>
	</html>