A Small Compiler for Explaining Delta Lake Pruning
How delta-explain turns one predicate and the Delta log into a trustworthy explanation of file pruning, through shared representation, safe rewrites, and conservative measurement.
Data-Engineering
Spark Is Not Just Lazy. Spark Compiles Dataflow.
Why calling Spark ’lazy’ is technically reductive, and how thinking of it as a dataflow compiler changes the way you design pipelines.
Fixing Skewed Nested Joins in Spark with Asymmetric Salting
In large-scale Spark pipelines, skew can occur when a single key carries a disproportionately large nested payload. Asymmetric salting offers a targeted solution: explode, salt, join in parallel, and optionally re-aggregate.
From Dictionary Indices to Integers: Parquet Bit Unpacking Explained
Parquet rarely stores a column’s values directly. Dictionary encoding keeps the distinct values once and represents the column through small bit-packed integer indices. This explainer walks through dictionary encoding, how the indices are bit-packed, and the bit-unpacking step that reconstructs them into an int[] before every dictionary lookup.