Reviewed by Aditya Kumar · Last reviewed 2026-03-24
**Why transformations matter**: Choice affects Catalyst optimization and performance. **Common**: map, filter, select, withColumn, drop, groupBy, agg, join, union, distinct. Window: row_number, rank, sum over. **Scalability trade-offs**: Narrow (map, filter) = no shuffle; wide...
Why transformations matter: Choice affects Catalyst optimization and performance. Common: map, filter, select, withColumn, drop, groupBy, agg, join, union, distinct. Window: row_number, rank, sum over. Scalability trade-offs: Narrow (map, filter) = no shuffle; wide (groupBy, join) = shuffle. Prefer narrow; minimize wide. Cost implications: UDF breaks optimization; built-ins preferred. Best practice: Prefer built-in; avoid UDF when possible; chain logically.
Red Flag: UDF for filter/select—built-ins exist. Pro-Move: 'We use built-ins; UDF only for custom business logic.'
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