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From Apache Wiki <wikidi...@apache.org>
Subject [Pig Wiki] Update of "LoadStoreMigrationGuide" by PradeepKamath
Date Thu, 11 Feb 2010 22:20:52 GMT
Dear Wiki user,

You have subscribed to a wiki page or wiki category on "Pig Wiki" for change notification.

The "LoadStoreMigrationGuide" page has been changed by PradeepKamath.
http://wiki.apache.org/pig/LoadStoreMigrationGuide?action=diff&rev1=16&rev2=17

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

  || No equivalent method || relToAbsPathForStoreLocation() || !StoreFunc || Pig runtime will
call this method to allow the Storer to convert a relative load 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 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() || 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.||
+ || 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.||
  || 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 close() in !RecordWriter
or commitTask in !OutputCommitter || !RecordWriter or !OutputCommitter || finish() has been
removed from !StoreFunc since the same semantics can be achieved by !RecordWriter.close()
or !OutputCommitter.commitTask() - in the latter case !OutputCommitter.needsTaskCommit() should
return true.||

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