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From: Apache Wiki <wikidiffs@apache.org>
To: Apache Wiki <wikidiffs@apache.org>
Date: Thu, 11 Feb 2010 22:20:52 -0000
Message-ID: <20100211222052.9961.44442@eos.apache.org>
Subject: 
 =?utf-8?q?=5BPig_Wiki=5D_Update_of_=22LoadStoreMigrationGuide=22_by_Prade?=
 =?utf-8?q?epKamath?=

Dear Wiki user,

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

The "LoadStoreMigrationGuide" page has been changed by PradeepKamath.
http://wiki.apache.org/pig/LoadStoreMigrationGuide?action=3Ddiff&rev1=3D16&=
rev2=3D17

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

  || No equivalent method || relToAbsPathForStoreLocation() || !StoreFunc |=
| Pig runtime will call this method to allow the Storer to convert a relati=
ve load location to an absolute location. An implementation is provided in =
!LoadFunc (as a static method) which handles this for hdfs files and direct=
ories.||
  || No equivalent method || checkSchema() || !StoreFunc || A Store functio=
n should implement this function to check that a given schema is acceptable=
 to it ||
  || No equivalent method || setStoreLocation() || !StoreFunc || This metho=
d is called by Pig to communicate the store location to the storer. The sto=
rer should use this method to communicate the same information to the under=
lying !OutputFormat. This method is called multiple times by pig - implemen=
tations should bear in mind that this method is called multiple times and s=
hould ensure there are no inconsistent side effects due to the multiple cal=
ls.||
- || getStorePreparationClass() || getOutputFormat() || In the old API, get=
StorePreparationClass() was the means by which the implementation could com=
municate 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 c=
alled 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 implementat=
ion could communicate to Pig the !OutputFormat to use for writing - this is=
 now achieved through getOutputFormat(). getOutputFormat() is NOT an option=
al method and implementation SHOULD provide an !OutputFormat to use. The me=
thods in the !OutputFormat (and underlying !RecordWriter and !OutputCommitt=
er) will be called by pig in the same manner (and in the same context) as b=
y Hadoop in a map-reduce java program.||
  || bindTo() || prepareToWrite() || !StoreFunc || bindTo() was the old met=
hod which would provide an !OutputStream among other things to the !StoreFu=
nc. 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() whe=
rein the !RecordWriter associated with the !OutputFormat provided by the !S=
toreFunc 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 n=
ot changed and is called by Pig runtime to write the next tuple of data - i=
n the new API, this is the method wherein the implementation will use the t=
he underlying !RecordWriter to write the Tuple out ||
  || finish() || no equivalent method in !StoreFunc - implementations can u=
se close() in !RecordWriter or commitTask in !OutputCommitter || !RecordWri=
ter or !OutputCommitter || finish() has been removed from !StoreFunc since =
the same semantics can be achieved by !RecordWriter.close() or !OutputCommi=
tter.commitTask() - in the latter case !OutputCommitter.needsTaskCommit() s=
hould return true.||