[GitHub] [arrow] jorisvandenbossche commented on issue #34319: [R] v11.0.0.2 extremely slow with parquet files written in v9.0.0

["jorisvandenbossche (via GitHub)" <gi...@apache.org>]

jorisvandenbossche commented on issue #34319:
URL: https://github.com/apache/arrow/issues/34319#issuecomment-1443965628

   I don't directly see a similar issue with pyarrow. Using the low-level reader (and a private method to be able to pass column indices directly instead of column names, to mimic what happens in R):
   
   ```
   In [1]: import pyarrow.parquet as pq
   
   In [2]: %timeit pq.ParquetFile("test_data.parquet").reader.read_all(column_indices=list(range(200)))
   146 ms ± 22 ms per loop (mean ± std. dev. of 7 runs, 10 loops each)
   ```
   
   That's with pyarrow 9.0, and I see basically the same for pyarrow 10.0.
   
   So maybe something changed with how the `col_select` keyword is being used?


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