Let's take a look at what is not supported in Impala so you can make informed decisions when choosing Impala as your distributed data-processing framework on Hadoop:
- Only HDFS is supported for data storage with Impala, and any other data storage framework or RDBMS is not currently supported.
- Impala does not support dropping or deleting a row in a table. The alternative is to either drop the table or migrate the required data to other tables and then delete the entire original table.
- Transforms and window functions are not supported.
- Performing queries on streaming data is not supported.
- Hive UDF and Hive Index are not supported up to Impala 1.1.x; however, at the time of writing this book, Impala 1.2 Beta was available, which has support for Scalar UDF and user-defined aggregate (UDA) functions.
- During query processing, unencrypted data is sometimes transmitted between Impala daemons.
- At the time of writing this book, Hadoop 2.0 achieved the GA milestone; however, Hadoop-2.0-based YARN is not integrated with Impala.
- Custom Hive SerDes classes are not supported and only native file formats are supported using the built-in SerDes.
Tip
Please visit this URL to learn about the new feature set available in Impala 1.2.x: http://www.cloudera.com/content/cloudera-content/cloudera-docs/Impala/latest/Cloudera-Impala-Release-Notes/cirn_new_features.html?scroll=new_features_121_unique_1.
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