What is SQL Server columnstore batch mode execution pipeline and how does vectorization work internally?

Batch mode processes multiple rows at once using vectorized execution to reduce CPU overhead.

Batch mode execution is a core optimization in columnstore indexes where SQL Server processes data in batches (often 64–900 rows) instead of row-by-row. Instead of interpreting operators per row, SQL Server applies SIMD-style vectorized operations on compressed column segments. This reduces CPU instruction overhead, improves cache locality, and enables higher throughput. Batch mode is tightly coupled with columnstore storage but can also be used in some rowstore scenarios via adaptive execution plans.