Checks <input type="c

In the former case, the plan is: <div class="snippet-clipboard-content notranslate

`scan_parquet` + `with_row_index` causing `pl.len()` to return 0 about polars HOT 1 CLOSED

cmdlineluser commented on June 25, 2024

`scan_parquet` + `with_row_index` causing `pl.len()` to return 0

from polars.

Comments (1)

wence- commented on June 25, 2024 3

In the former case, the plan is:

                 0
   ┌─────────────────────────
   │
   │     ╭───────────────╮
 0 │     │ FAST COUNT(*) │
   │     ╰───────┬───────╯
   │             │
   │             │
   │             │
   │  ╭──────────┴──────────╮
   │  │ DF []               │
 1 │  │ PROJECT */0 COLUMNS │
   │  ╰─────────────────────╯

In the latter, it is:

             0                                  1
   ┌───────────────────────────────────────────────────────────────────────
   │
   │     ╭────────╮
 0 │     │ SELECT │
   │     ╰───┬┬───╯
   │         ││
   │         │╰─────────────────────────────────╮
   │         │                                  │
   │         │         ╭────────────────────────┴─────────────────────────╮
   │  ╭──────┴──────╮  │ FROM:                                            │
   │  │ expression: │  │  SELECT [len()] FROM                             │
 1 │  │ len()       │  │                                                  │
   │  ╰─────────────╯  │     Parquet SCAN /tmp/tmppxstkd22/polars.parquet │
   │                   │     PROJECT */3 COLUMNS                          │
   │                   ╰──────────────────────────────────────────────────╯

In the latter case, column projection produces an IR scanning the parquet file projecting out all columns (the with_columns option is the empty list). And then (presumably) len of an empty table produces zero.

from polars.

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