The Drillbit daemon plays a crucial role in Apache Drill’s distributed query execution. It runs on each node of the cluster, enabling parallel processing and efficient data locality. When a client submits a query, the Foreman (a designated Drillbit) coordinates the planning and distribution of tasks among available Drillbits.
Drillbit manages query execution through two primary components: the optimizer and the execution engine. The optimizer generates an optimal physical plan based on cost estimation and rule-based transformations. This plan is then divided into fragments, which are assigned to Drillbits for parallel execution.
During execution, Drillbits communicate with each other to exchange intermediate results and perform operations like filtering, aggregation, or join. They also leverage local storage systems such as HDFS or MapR-FS to read and write data efficiently. Upon completion, final results are sent back to the client.
