Apache Drill’s query planning process involves three main stages: logical plan, physical plan, and execution plan. The logical plan represents the initial SQL query as a tree of relational operators, such as scans, filters, and joins. It is created by parsing and validating the input SQL query.
The physical plan transforms the logical plan into a distributed processing representation, considering factors like data locality and parallelism. This stage uses rule-based optimization techniques to generate an efficient plan for executing the query across multiple nodes in the cluster.
The execution plan further refines the physical plan by generating executable code for each operator in the plan. This code is then compiled and executed on the appropriate nodes within the cluster, with results being streamed back to the client.
