Apache Impala is the open source, native analytic database for Apache Hadoop. Impala is shipped by Cloudera, MapR, Oracle, and Amazon.
Introduction from the whitepaper Impala: A Modern, Open-Source SQL Engine for Hadoop:
INTRODUCTION
Impala is an open-source, fully-integrated, state-of-the-art MPP SQL query engine designed specifically to leverage the flexibility and scalability of Hadoop. Impala’s goal is to combine the familiar SQL support and multi-user performance of a traditional analytic database with the scalability and flexibility of Apache Hadoop and the production-grade security and management extensions of Cloudera Enterprise. Impala’s beta release was in October 2012 and it GA’ed in May 2013. The most recent version, Impala 2.0, was released in October 2014. Impala’s ecosystem momentum continues to accelerate, with nearly one million downloads since its GA.
Unlike other systems (often forks of Postgres), Impala is a brand-new engine, written from the ground up in C++ and Java. It maintains Hadoop’s flexibility by utilizing standard components (HDFS, HBase, Metastore, YARN, Sentry) and is able to read the majority of the widely-used file formats (e.g. Parquet, Avro, RCFile). To reduce latency, such as that incurred from utilizing MapReduce or by reading data remotely, Impala implements a distributed architecture based on daemon processes that are responsible for all aspects of query execution and that run on the same machines as the rest of the Hadoop infrastructure. The result is performance that is on par or exceeds that of commercial MPP analytic DBMSs, depending on the particular workload.
...
Impala is the highest performing SQL-on-Hadoop system, especially under multi-user workloads. As Section 7 shows, for single-user queries, Impala is up to 13x faster than alter- natives, and 6.7x faster on average. For multi-user queries, the gap widens: Impala is up to 27.4x faster than alternatives, and 18x faster on average – or nearly three times faster on average for multi-user queries than for single-user ones.
