Hadoop Essentials by Achari Shiva

Author:Achari, Shiva
Language: eng
Format: epub
Publisher: Packt Publishing
Published: 2015-04-29T04:00:00+00:00

ILLUSTRATE

The ILLUSTRATE command is perhaps the most important development aid. ILLUSTRATE on a relation samples the data and applies the query on it. This can save a lot of time during the debugging process. The sample is significantly smaller than the data making the code, test, and, debug cycle very fast. In many situations, JOIN or FILTER operators may not yield any output on a sample of the data. In such cases, ILLUSTRATE manufactures records that pass through these operators and inserts them into the sample dataset:

grunt> illustrate grouped; ----------------------------------------------------------- | owners | owner:chararray | animal:chararray | ----------------------------------------------------------- | | steve | dog | | | adam | dog | ----------------------------------------------------------- -------------------------------------------------------- | pets | name:chararray | animal:chararray | -------------------------------------------------------- | | fido | dog | | | rex | dog | -------------------------------------------------------- -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | grouped | group:chararray | owners:bag{:tuple(owner:chararray,animal:chararray)} | pets:bag{:tuple(name:chararray,animal:chararray)} | -------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- | | dog | {(steve, dog), (adam, dog)} | {(fido, dog), (rex, dog)} | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------

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