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`get_dataframe_report()` raises TypeError when a step has `columns_subset` (rows_distinct, rows_complete)

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  • #446 by @manan28025 — closed without merging

Assessment

Difficulty
2/5
Estimated time
1-3 hours
Newbie friendliness
76/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
python
Domain
data

Research direction

Start in get_dataframe_report() and inspect the pl_schema definition for the column field, then trace how rows_distinct() and rows_complete() with columns_subset= populate validation_info[i].column. Reproduce with the supplied example and check the report’s column values for both subset steps after the change; the report should build without a TypeError and retain the selected column names.

Written by the indexing model from the issue text.

Description

Description

Validate.get_dataframe_report() fails with a Polars TypeError as soon as the plan contains a step whose column is a list, i.e. rows_distinct() or rows_complete() with columns_subset=. The whole report is lost, not just that step.

Reproducer

import polars as pl
import pointblank as pb

df = pl.DataFrame({"a": [1, 2, 2], "b": ["x", "y", None]})

pb.Validate(df).rows_distinct().interrogate().get_dataframe_report()            # OK
pb.Validate(df).rows_distinct(columns_subset=["a"]).interrogate().get_dataframe_report()

Error:

TypeError: unexpected value while building Series of type String; found value of type List(String): ["a"]

Hint: Try setting `strict=False` to allow passing data with mixed types.

Same result with rows_distinct(columns_subset=["a", "b"]) and rows_complete(columns_subset=["a", "b"]). Steps where columns= is a list (e.g. col_vals_gt(columns=["a"])) are fine, since they are expanded into one step per column.

Reproduced on 0.24.0 (where the method was added in #341), 0.27.0 and 1.0.1.

Cause

In get_dataframe_report(), the Polars schema declares the column field as a string (line 21497 on main at 4510729):

pl_schema = pl.Schema(
    {
        ...
        "column": pl.String,
        ...
    }
)

For rows_distinct() / rows_complete() with columns_subset=, validation_info[i].column is a list of names, so pl.DataFrame(data=final_report, schema=pl_schema) fails.

Possible fix

Normalize list values before building the frame, e.g. join them into a string ("a, b"), which keeps columns a String column for every step. Alternatively declare it as pl.List(pl.String) and wrap single names in a list, though that changes the column type for all users.

Environment

  • pointblank 1.0.1
  • polars 1.38.1
  • Python 3.12.7
  • Linux

Found while using pointblank in fauxdata.

Dominant language
Python
Stars
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Forks
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Avg merge
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Merged PRs (30d)
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