GH-35806: [R] Improve error message for null type inference with sparse CSV data#49338
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thisisnic wants to merge 4 commits intoapache:mainfrom
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GH-35806: [R] Improve error message for null type inference with sparse CSV data#49338thisisnic wants to merge 4 commits intoapache:mainfrom
thisisnic wants to merge 4 commits intoapache:mainfrom
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…h sparse CSV data When a CSV column contains only missing values in the first block of data, Arrow infers the type as null. If a non-null value appears later, the conversion fails with an unhelpful error suggesting `skip = 1`. This change adds a specific check for "conversion error to null" and provides a more helpful message explaining the cause (type inference from sparse data) and the solution (specify column types explicitly). Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>
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I'm not totally happy with the error message, will rewrite before marking ready for review |
thisisnic
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Feb 23, 2026
thisisnic
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I like the improved message, though I'm not totally sure I follow why we can assert the reason for why null was inferred? And also wouldn't this similarly error if someone specified null manually and then there was data(??)
| msg <- c( | ||
| msg, | ||
| i = paste( | ||
| "Column type was inferred as null because the first block of data", |
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Suggested change
| "Column type was inferred as null because the first block of data", | |
| "Column type was inferred as `null` because the first block of data", |
or maybe even NULL?
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Rationale for this change
When reading a CSV with sparse data (many missing values followed by actual values), Arrow can infer a column type as
nullbased on the first block of data. When non-null values appear later, the error message incorrectly suggests usingskip = 1for header rows, which is misleading.What changes are included in this PR?
Adds a specific check for "conversion error to null" that provides a helpful message explaining the cause (type inference from sparse data) and the solution (change the block size to use for inference).
Are these changes tested?
Yes, added a test in
test-dataset-csv.R.Are there any user-facing changes?
Yes, improved error message when CSV type inference fails due to sparse data.
This PR was authored by Claude (Opus 4.5) and reviewed by @thisisnic.
🤖 Generated with Claude Code