LazyFrame.forEachBatch

Consumes the deferred frame batch-by-batch without accumulating the output: each pulled batch (the row-wise prefix applied, the limit bound honored) is handed to consumer; returning false stops pulling (the early-exit rule). When nothing ever arrives, the consumer sees one empty schema-carrying batch (a sink still writes its header). Blocking plans materialise through collect() first - disclosed by streamMode() - and are then iterated in batchSize batches.