Dynamic Speculative Optimizations for SQL Compilation in Apache Spark

Big-data systems have gained significant momentum, and Apache Spark is becoming a de-facto standard for modern data analytics. Spark relies on SQL query compilation to optimize the execution performance of analytical workloads on a variety of data sources. Despite its scalable architecture, Spark's SQL code generation suffers from significant runtime overheads related to data access and de-serialization. Such performance penalty can be significant, especially when applications operate on human-readable data formats such as CSV or JSON. In this paper we present a new approach to query compilation that overcomes these limitations by relying on run-time profiling and dynamic code generation. Our new SQL compiler for Spark produces highly-efficient machine code, leading to speedups of up to 4.4x on the TPC-H benchmark with textual-form data formats such as CSV or JSON.