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The "LoadStoreMigrationGuide" page has been changed by PradeepKamath.
http://wiki.apache.org/pig/LoadStoreMigrationGuide?action=diff&rev1=26&rev2=27

--------------------------------------------------

  This page describes how to migrate from the old !LoadFunc and !StoreFunc 
interface (Pig 0.1.0 through Pig 0.6.0) to the new interfaces proposed in 
http://wiki.apache.org/pig/LoadStoreRedesignProposal and planned to be released 
in Pig 0.7.0. Besides the example in this page, users can also look at 
!LoadFunc and !StoreFunc implementation in the piggybank codebase 
(contrib/piggybank/java/src/main/java/org/apache/pig/piggybank/storage) for 
examples of migration. For example, !MultiStorage implements a custom 
!OutputFormat.
  
- '''A general note applicable to both !LoadFunc and !StoreFunc implementations 
is that the implementation should use the new Hadoop 20 API based classes 
(!InputFormat/OutputFormat and related classes) in org.apache.hadoop.mapreduce 
package instead of the old org.apache.hadoop.mapred package.'''
+ '''A general note applicable to both !LoadFunc and !StoreFunc implementations 
is that the implementation should use the new Hadoop 20 API based classes 
(!InputFormat/OutputFormat and related classes) under the 
org.apache.hadoop.mapreduce package instead of the old org.apache.hadoop.mapred 
package.'''
  
  The main motivation for these changes is to move closer to using Hadoop's 
!InputFormat and !OutputFormat classes. This way pig users/developers can 
create new !LoadFunc and !StoreFunc implementation based on existing Hadoop 
!InputFormat and !OutputFormat classes with minimal code. The complexity of 
reading the data and creating a record will now lie in the !InputFormat and 
likewise on the writing end, the complexity of writing will lie in the 
!OutputFormat. This enables !Pig to easily read/write data in new storage 
formats as and when an Hadoop !InputFormat and !OutputFormat is available for 
them.
  
@@ -21, +21 @@

  ||No equivalent method ||relativeToAbsolutePath() ||!LoadFunc ||Pig runtime 
will call this method to allow the Loader to convert a relative load location 
to an absolute location. The default implementation provided in !LoadFunc 
handles this for hdfs files and directories. If the load source is something 
else, loader implementation may choose to override this. ||
  ||determineSchema() ||getSchema() ||!LoadMetadata ||determineSchema() was 
used by old code to ask the loader to provide a schema for the data returned by 
it - the same semantics are now achieved through getSchema() of the 
!LoadMetadata interface. !LoadMetadata is an optional interface for loaders to 
implement - if a loader does not implement it, this will indicate to the pig 
runtime that the loader cannot return a schema for the data ||
  ||fieldsToRead() ||pushProject() ||!LoadPushDown ||fieldsToRead() was used by 
old code to convey to the loader the exact fields required by the pig script 
-the same semantics are now achieved through pushProject() of the !LoadPushDown 
interface. !LoadPushDown is an optional interface for loaders to implement - if 
a loader does not implement it, this will indicate to the pig runtime that the 
loader is not capable of returning just the required fields and will return all 
fields in the data. If a loader implementation is able to efficiently return 
only required fields, it should implement !LoadPushDown to improve query 
performance ||
- ||No equivalent method ||getInputFormat() ||!LoadFunc ||This method will be 
called by Pig to get the !InputFormat used by the loader. The methods in the 
!InputFormat (and underlying !RecordReader) will be called by pig in the same 
manner (and in the same context) as by Hadoop in a map-reduce java program. 
'''If the !InputFormat is a hadoop packaged one, the implementation should use 
the new API based one in org.apache.hadoop.mapreduce. If it is a custom 
!InputFormat, it should be implemented using the new API in 
org.apache.hadoop.mapreduce'''||
+ ||No equivalent method ||getInputFormat() ||!LoadFunc ||This method will be 
called by Pig to get the !InputFormat used by the loader. The methods in the 
!InputFormat (and underlying !RecordReader) will be called by pig in the same 
manner (and in the same context) as by Hadoop in a map-reduce java program. 
'''If the !InputFormat is a hadoop packaged one, the implementation should use 
the new API based one under org.apache.hadoop.mapreduce. If it is a custom 
!InputFormat, it should be implemented using the new API in 
org.apache.hadoop.mapreduce'''||
  ||No equivalent method ||setLocation() ||!LoadFunc ||This method is called by 
Pig to communicate the load location to the loader. The loader should use this 
method to communicate the same information to the underlying !InputFormat. This 
method is called multiple times by pig - implementations should bear in mind 
that this method is called multiple times and should ensure there are no 
inconsistent side effects due to the multiple calls. ||
  ||bindTo() ||prepareToRead() ||!LoadFunc ||bindTo() was the old method which 
would provide an !InputStream among other things to the !LoadFunc. The 
!LoadFunc implementation would then read from the !InputStream in getNext(). In 
the new API, reading of the data is through the !InputFormat provided by the 
!LoadFunc. So the equivalent call is prepareToRead() wherein the !RecordReader 
associated with the !InputFormat provided by the !LoadFunc is passed to the 
!LoadFunc. The !RecordReader can then be used by the implementation in 
getNext() to return a tuple representing a record of data back to pig. ||
  ||getNext() ||getNext() ||!LoadFunc ||The meaning of getNext() has not 
changed and is called by Pig runtime to get the next tuple in the data - in the 
new API, this is the method wherein the implementation will use the the 
underlying !RecordReader and construct a tuple ||
@@ -39, +39 @@

  ||No equivalent method ||relToAbsPathForStoreLocation() ||!StoreFunc ||Pig 
runtime will call this method to allow the Storer to convert a relative store 
location to an absolute location. An implementation is provided in !LoadFunc 
(as a static method) which handles this for hdfs files and directories. ||
  ||No equivalent method ||checkSchema() ||!StoreFunc ||A Store function should 
implement this function to check that a given schema describing the data to be 
written is acceptable to it ||
  ||No equivalent method ||setStoreLocation() ||!StoreFunc ||This method is 
called by Pig to communicate the store location to the storer. The storer 
should use this method to communicate the same information to the underlying 
!OutputFormat. This method is called multiple times by pig - implementations 
should bear in mind that this method is called multiple times and should ensure 
there are no inconsistent side effects due to the multiple calls. ||
- ||getStorePreparationClass() ||getOutputFormat() ||!StoreFunc ||In the old 
API, getStorePreparationClass() was the means by which the implementation could 
communicate to Pig the !OutputFormat to use for writing - this is now achieved 
through getOutputFormat(). getOutputFormat() is NOT an optional method and 
implementation SHOULD provide an !OutputFormat to use. The methods in the 
!OutputFormat (and underlying !RecordWriter and !OutputCommitter) will be 
called by pig in the same manner (and in the same context) as by Hadoop in a 
map-reduce java program. '''If the !OutputFormat is a hadoop packaged one, the 
implementation should use the new API based one in org.apache.hadoop.mapreduce. 
If it is a custom !OutputFormat, it should be implemented using the new API in 
org.apache.hadoop.mapreduce'''. The checkOutputSpecs() method of the 
!OutputFormat will be called by pig to check the output location up-front. This 
method will also be called as part of the Hadoop call sequence when the job is 
launched. So implementations should ensure that this method can be called 
multiple times without inconsistent side effects. ||
+ ||getStorePreparationClass() ||getOutputFormat() ||!StoreFunc ||In the old 
API, getStorePreparationClass() was the means by which the implementation could 
communicate to Pig the !OutputFormat to use for writing - this is now achieved 
through getOutputFormat(). getOutputFormat() is NOT an optional method and 
implementation SHOULD provide an !OutputFormat to use. The methods in the 
!OutputFormat (and underlying !RecordWriter and !OutputCommitter) will be 
called by pig in the same manner (and in the same context) as by Hadoop in a 
map-reduce java program. '''If the !OutputFormat is a hadoop packaged one, the 
implementation should use the new API based one in org.apache.hadoop.mapreduce. 
If it is a custom !OutputFormat, it should be implemented using the new API 
under org.apache.hadoop.mapreduce'''. The checkOutputSpecs() method of the 
!OutputFormat will be called by pig to check the output location up-front. This 
method will also be called as part of the Hadoop call sequence when the job is 
launched. So implementations should ensure that this method can be called 
multiple times without inconsistent side effects. ||
  ||bindTo() ||prepareToWrite() ||!StoreFunc ||bindTo() was the old method 
which would provide an !OutputStream among other things to the !StoreFunc. The 
!StoreFunc implementation would then write to the !OutputStream in putNext(). 
In the new API, writing of the data is through the !OutputFormat provided by 
the !StoreFunc. So the equivalent call is prepareToWrite() wherein the 
!RecordWriter associated with the !OutputFormat provided by the !StoreFunc is 
passed to the !StoreFunc. The !RecordWriter can then be used by the 
implementation in putNext() to write a tuple representing a record of data in a 
manner expected by the !RecordWriter. ||
  ||putNext() ||putNext() ||!StoreFunc ||The meaning of putNext() has not 
changed and is called by Pig runtime to write the next tuple of data - in the 
new API, this is the method wherein the implementation will use the the 
underlying !RecordWriter to write the Tuple out ||
  ||finish() ||no equivalent method in !StoreFunc - implementations can use 
commitTask() in !OutputCommitter ||!OutputCommitter ||finish() has been removed 
from !StoreFunc since the same semantics can be achieved by 
!OutputCommitter.commitTask() - (!OutputCommitter.needsTaskCommit() should 
return true to be able to use commitTask()). ||

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