Apache Kylin is an open source analytics solution from eBay Inc. that enables SQL based multidimensional analysis (OLAP) on very large datasets. Kylin is intended to be a Hadoop based hybrid OLAP (HOLAP) solution that will eventually support both MOLAP and ROLAP style multidimensional analysis. With Kylin you can define cubes using a Cube Designer and initiate an offline process that builds these cubes. The offline process performs a pre-join step to join facts and dimension tables into a flattened out structure. This is followed by a pre-aggregation phase where individual cuboids are built using Map Reduce jobs. The results are stored in HDFS sequence files and are later loaded into HBase. The data requests can originate from SQL submitted using a SQL-based tool. The query engine (based on Apache Calcite ), determines if the target dataset exists in HBase. If so, the engine directly accesses the target data from HBase and returns the result with sub-second latency. If not, the engine routes the queries to Hive (or any other SQL on Hadoop solution enabled on the cluster).
