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From Apache Wiki <wikidi...@apache.org>
Subject [Pig Wiki] Update of "LoadStoreMigrationGuide" by PradeepKamath
Date Wed, 10 Feb 2010 20:26:17 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=7&rev2=8

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

  || getNext() || getNext() || !LoadFunc || The meaning of getNext() has not changed and is
called by Pig runtime to get the next tuple in the data ||
  || bytesToInteger(),...bytesToBag() ||  bytesToInteger(),...bytesToBag() || !LoadCaster
|| The meaning of these methods has not changed and is called by Pig runtime to cast a !DataByteArray
fields to the right type when needed. In the new API, a !LoadFunc implementation should give
a !LoadCaster object back to pig as the return value of getLoadCaster() method so that it
can be used for casting. If a null is returned then casting from !DataByteArray to any other
type (implicitly or explicitly) in the pig script will not be possible ||
  || 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||
- || 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 || 
+ || 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 ||
  
  == Old Implementation ==
  {{{

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