Apache Calcite
Apache Calcite is an open source framework for
building databases and data management systems.
It includes a SQL parser,
an API for building expressions in relational algebra,
and a query planning engine.
As a framework, Calcite does not store its own data or metadata,
but instead allows external data and metadata to be accessed by means of plug-ins.
Several other Apache projects use Calcite.
Hive uses Calcite for cost-based query optimization;
Drill and Kylin use Calcite for SQL parsing and optimization;
Samza and Storm use Calcite for streaming SQL.
, Apex, Phoenix and Flink have projects under development that use Calcite. Since 2019, LeanXcale query engine is based on Apache Calcite.
