The Photon Engine
/tldr: The native vectorized query engine written in C++ that powers high-performance data processing on Databricks.
1. Defining Photon
Photon is a second-generation query engine designed to dramatically accelerate Apache Spark 3.0+ workloads. It is **compatible with the Spark API** but completely re-engineered under the hood to maximize performance on modern cloud hardware.
The Problem Photon Solves
Traditional Spark engines (written primarily in Scala/Java) can suffer from overhead due to JVM object instantiation, garbage collection, and interpreting bytecode. Photon bypasses these issues, delivering performance typical of dedicated C++ data warehouses.
2. Mechanisms for Acceleration
Vectorized Query Processing
Instead of processing data row-by-row, Photon processes data in large batches (vectors). This technique drastically reduces the overhead of function calls and control flow logic.
C++ Native Implementation
Writing the core execution engine in C++ allows for direct memory management and tight coupling with CPU instructions, specifically leveraging **SIMD** (Single Instruction, Multiple Data) instructions for parallel execution.
Just-In-Time (JIT) Compilation
Photon compiles query fragments down to optimized native machine code during runtime. This maximizes CPU efficiency by ensuring the code executed is perfectly tailored for the specific data types and operations of the query.
Optimized Delta Lake I/O
It is deeply integrated with Delta Lake, providing accelerated data scanning, pruning, and predicate pushdown. This minimizes the data read from cloud storage, especially for large tables.
3. Deployment and Availability
Photon is available across the Databricks platform wherever high-performance Spark execution is needed.
Databricks SQL Warehouses (DB SQL)
Default Engine: Photon is the foundational execution engine for all Databricks SQL Warehouses (Classic, Pro, and Serverless). This is where its performance difference is most noticeable for BI and analytical queries.
Data Engineering Workloads
In Databricks Runtime (DBR) 9.1 LTS and newer, Photon can be enabled for standard Databricks Clusters running notebook and job tasks. It accelerates ETL/ELT transformations written in Python, Scala, or SQL.
Delta Live Tables (DLT)
DLT pipelines automatically leverage Photon for high-speed processing and stream/batch unification, ensuring fast, cost-effective data ingestion and transformation.
In short, Photon transforms the open-source Lakehouse architecture into a high-performance Data Warehouse competitor.