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a column file format
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Trevni is a column-oriented file-format. The Trevni specification is published at: http://cutting.github.com/trevni/spec.html Java Implementation Currently only a Java implementation exists. Other implementations are encouraged. The Java implementation has a low-level API in the trevni-core module, with classes in the package org.apache.trevni. A higher-level API based on Avro is included in the trevni-avro module, with classes in the package org.apache.trevni.avro. This includes a Hadoop OutputFormat and InputFormat. One may write data for an Avro schema to a Trevni file using the output format in a MapReduce job. Then one may efficiently read a subset of that Schema in subsequent MapReduce jobs. For example, if one has a large schema with many complex fields, but has a job that only requires access to a few of those fields, one can delete everything but the desired fields from the schema and use that subset schema to read the data. Avro also supports subsetting, but it must scan through the skipped fields, while, as a column format, Trevni will only read data from disk for the fields that are desired. Some command-line tools for dumping Trevni files as JSON are provided in the trevni-tools module. Requirements - Java 6 or higher, Java 7 preferred - Maven - Git To get the code: git clone git://github.com/cutting/trevni.git To build the javadoc: cd trevni mvn test -DskipTests javadoc:aggregate firefox target/site/apidocs/index.html To build and run the command-line tools: cd trevni mvn -DskipTests package java -jar java/tool/target/trevni-tools-0.1-SNAPSHOT.jar The tests provide some examples of uses.