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From Apache Wiki <wikidi...@apache.org>
Subject [Hadoop Wiki] Update of "Avro/Glossary" by JeffHammerbacher
Date Wed, 02 Dec 2009 02:38:53 GMT
Dear Wiki user,

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The "Avro/Glossary" page has been changed by JeffHammerbacher.


   * '''block''': Array and Maps are encoded as a series of blocks, with a "count" long at
the beginning of each block (and optionally "size"). Used for reading and writing data structures
that don't fit into memory (maybe; not implemented yet). May also refer to the "blocks" in
a file object container.
   * '''!DatumReader'''/'''!DatumWriter'''
   * '''!DataFileReader'''/'''!DataFileWriter'''
+  * '''Projection''': The ability to select a subset of data from an Avro schema by specifying
an "expected" schema with the objects you'd like to read. Can possibly avoid the overhead
of deserialization of all columns when you only want a few.
  === IPC ===
   * '''requestor'''
@@ -13, +14 @@

   * '''transceiver'''
  === Other ===
-  * '''specific'''
+  * '''specific''': take advantage of language-specific features when implementing a schema
(e.g. code generation of Java classes in the Java implementation).
   * '''generic'''
-  * '''reflect'''
+  * '''reflect''': generate an Avro schema by looking
  Most Avro terms of art are defined in the [[http://hadoop.apache.org/avro/docs/current/spec.html|specification]].

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