andygrove commented on issue #3457:
URL: 
https://github.com/apache/datafusion-comet/issues/3457#issuecomment-5034646880

   Closing this in favour of #4988, which carries the investigation forward 
with measurements.
   
   Most of what this issue asked for already shipped in #4722: 
`COMET_RESPECT_PARQUET_FILTER_PUSHDOWN` is gone, and format-level pruning (row 
group statistics, page index, bloom filters) now runs by default whenever 
Spark's `spark.sql.parquet.filterPushdown` is enabled. The chart in the 
description predates that change and the DataFusion 54 upgrade, so it no longer 
describes current behaviour.
   
   What remains is narrower than the original title: row-level `RowFilter` 
evaluation plus late materialization, behind 
`spark.comet.parquet.rowFilterPushdown.enabled` (default `false`). I 
benchmarked that flag on TPC-H SF100 Q1 and Q6. Q1 is roughly neutral, Q6 
regresses 47-81% depending on cache state, and scan metrics show why: bytes 
scanned is byte-for-byte identical with the flag on, while decode time is 2.5x 
higher, because Q6's predicate is uncorrelated with physical row order so late 
materialization can never eliminate a page.
   
   Details, per-iteration scan metrics, and proposed work items are in #4988.


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