A deep technical exploration of implementing a Miller-like CLI data pipeline tool in Java, achieving high-performance AVX-512 code generation from the JVM's JIT compiler without custom bytecode generation. The author introduces 'manual reification' — a technique using annotation processors and runtime class generation (via Cojen Maker) to hoist runtime values into static final fields, enabling the JIT to fully inline, devirtualize, and vectorize code that would otherwise suffer from polymorphic dispatch. Key techniques include: using Object[] register files with constant indices for scalar replacement on GraalVM, cache-fitted batch sizing using L1d topology, runtime speculative specialization for low-cardinality grouped reductions, and whole-pipeline stage fusion. The post benchmarks against Miller (Go) and Polars, showing the warmed-up JVM implementation can surpass both for large datasets, while also honestly discussing JVM startup overhead and the fragility of the fused pipeline approach.
