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| <body> |
| <h2>org.apache.hadoop.mapred.lib.db Package</h2> |
| <p> |
| This package contains a library to read records from a database as an |
| input to a mapreduce job, and write the output records to the database. |
| </p> |
| <p> |
| The Database to access can be configured using the static methods in the |
| DBConfiguration class. Jobs reading input from a database should use |
| DBInputFormat#setInput() to set the configuration. And jobs writing |
| its output to the database should use DBOutputFormat#setOutput(). |
| </p> |
| <p> |
| Tuples from/to the database are converted to/from Java objects using |
| DBWritable methods. Typically, for each table in the db, a class extending |
| DBWritable is defined, which holds the fields of the tuple. The fields |
| of a record are read from the database using DBWritable#readFields(ResultSet), |
| and written to the database using DBWritable#write(PreparedStatament |
| statement). |
| </p> |
| <p> |
| An example program using both DBInputFormat and DBOutputFormat can be found |
| at src/examples/org/apache/hadoop/examples/DBCountPageview.java. |
| </p> |
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