Fix csv quoted value inference by merterbak · Pull Request #25015 · NVIDIA/cudf

merterbak · 2026-11-02T22:18:12Z

Description

CSV reader always read quoted values as strings, so a value like "-1" could not be merged with an integer column. This PR strips the enclosing quotes before detecting the type, while a value with an unmatched quote. Such as 5", stays a string.

Checklist

I am familiar with the Contributing Guidelines.
New or existing tests cover these changes.
The documentation is up to date with these changes.

copy-pr-bot · 2026-11-02T22:18:16Z

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coderabbitai · 2026-11-02T22:20:31Z

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Summary

Summary by CodeRabbit

Bug Fixes
- Improved CSV type inference for quoted and unquoted numbers, booleans, and infinity values.
- Quote characters that do not enclose a field are preserved as text during type inference.
- CSV columns containing quoted integers retain integer types in supported merge workflows.
- Added coverage for CSV quoting options and mixed quoted and unquoted values.
New Features
- The string-transform example reads country and area codes as text, preserving their formatting.

CSV type inference now applies quote and whitespace handling when detecting values such as numbers, booleans, and infinities. C++ and Python tests cover quoted values and quoted-integer merges. The string-transforms example reads two columns as strings.

Changes: CSV quoted-value inference

Layer / File(s)	Summary
Inference rules and validation `cpp/src/io/csv/csv_gpu.cu`, `cpp/tests/io/csv_test.cpp`, `python/cudf/cudf/tests/input_output/test_csv.py`, `python/cudf/cudf_pandas_tests/test_cudf_pandas_no_fallback.py`	Inference checks boolean and infinity tokens against quote-trimmed fields. It trims whitespace first and removes quotes only under specified conditions. Tests cover quoted values, unmatched quotes, cuDF and pandas inference, and right merges with quoted integer values.

String-transforms example configuration

Layer / File(s)	Summary
String column types `cpp/examples/string_transforms/common.hpp`	The example maps `"Country Code"` and `"Area Code"` to string types when it reads the CSV.

Estimated code review effort: 3 (Moderate) | ~20 minutes

Change: Bug fix · Severity of issue fixed: Medium

Possibly related PRs

NVIDIA/cudf#24823: It changes how data_type_detection finds CSV field boundaries, which affects the field processed by this PR's quote handling.

Suggested labels: bug, non-breaking

Merge Risk: Moderate · up to cf6df

Some quoted CSV inputs can still produce incorrect inferred dtypes, so these edge cases should be addressed before merge.

Pre-merge checks: 5

Check name	Status	Explanation
Title check		The title "Fix csv quoted value inference" matches the main change. The PR makes the CSV reader strip enclosing quotes before type detection, so quoted values such as "-1" infer as integers. The title…
Description check		The description states the problem: the CSV reader always read quoted values as strings, so "-1" could not merge with an integer column. It states the fix: enclosing quotes are stripped before type de…
Linked Issues check		Issue `#24833` requirements are met. In `cpp/src/io/csv/csv_gpu.cu`, type detection removes enclosing quotes before numeric inference and keeps an unpaired quote such as `5"` in the field. The test `tes…
Out of Scope Changes check		The changed files support issue `#24833`. The CUDA change implements quoted-value type inference. The C++ and Python tests verify the inference and file-based merge behavior. The string-transform exampl…
Docstring Coverage		Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentat…

Full details: Title check

Explanation

The title "Fix csv quoted value inference" matches the main change. The PR makes the CSV reader strip enclosing quotes before type detection, so quoted values such as "-1" infer as integers. The title is short, specific, and describes the primary fix. It does not name the cudf scope, but that detail is not required.

Full details: Description check

Explanation

The description states the problem: the CSV reader always read quoted values as strings, so "-1" could not merge with an integer column. It states the fix: enclosing quotes are stripped before type detection, and values with an unmatched quote stay strings. It references issue #24833 and includes the checklist. The description is directly related to the changeset.

Full details: Linked Issues check

Explanation

Issue #24833 requirements are met. In cpp/src/io/csv/csv_gpu.cu, type detection removes enclosing quotes before numeric inference and keeps an unpaired quote such as 5" in the field. The test test_no_fallback_in_merge_quoted_csv_integer writes a CSV file, verifies int64 inference for "-1", "0", and "42", and verifies the one-row right merge with the expected integer value. C++ and CSV reader tests cover quoted numeric, boolean, infinity, mixed, and malformed-quote values.

Full details: Out of Scope Changes check

Explanation

The changed files support issue #24833. The CUDA change implements quoted-value type inference. The C++ and Python tests verify the inference and file-based merge behavior. The string-transform example preserves string types for code columns that can be affected by changed inference. No unrelated implementation or test change is established.

Full details: Docstring Coverage

Explanation

Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff with cyclomatic complexity of at least 2. Documentation-only edits and deletions within surviving functions are included; unchanged diff context and fully deleted functions are excluded. Analyzed 2 functions across 5 files.

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Follow-up Comments

Normalize whitespace before matching quoted boolean and infinity tokens.

200-205: Major · Functional Correctness · Quick win

Normalize whitespace before matching quoted boolean and infinity tokens.

When opts.detect_whitespace_around_quotes is enabled, "true" reaches trim_quotes with whitespace at both ends. unquoted_field therefore still contains the quotes, so the trie check misses true and the later scan classifies the value as STRING. The same issue affects "inf" .

Build unquoted_field from the whitespace-trimmed range, using the same option-dependent quote rule as lines 223-226. Add inference coverage for quoted boolean and infinity values with surrounding whitespace.

As per coding guidelines, logic errors producing wrong results must be flagged.

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Review comment at @cpp/src/io/csv/csv_gpu.cu around lines 200 - 205:
Update the field range used by trim_quotes and the boolean-token trie checks to
trim surrounding whitespace when opts.detect_whitespace_around_quotes is
enabled, applying the same option-dependent quote rule as the existing inference
logic. Ensure quoted boolean and infinity values with surrounding whitespace are
inferred correctly, and add inference coverage for both cases.
Source: Coding guidelines

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Exclude thousands separators from the integer range check.

286-287: Major · Data Integrity & Integration · Quick win

Exclude thousands separators from the integer range check.

The PR now removes the configured quote character before numeric inference, so a quoted value such as "9,999,999,999,999,999,999" reaches infer_integral_field_counter. That helper compares the supplied range without skipping thousands separators, so the value can be classified as an INT64-range value instead of a UINT64 value. The same separator defect already affects unquoted values, but this PR newly exposes it for quoted numeric fields.

Pass the full field range and skip separators during the range comparison.

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Review comment at @cpp/src/io/csv/csv_gpu.cu around lines 286 - 287:
Update the integer inference path around infer_integral_field_counter to compare
the full field range while excluding configured thousands separators from the
range check. Preserve the existing quote-removal behavior, and use the helper’s
supported separator-handling mechanism rather than truncating or otherwise
altering the field range.

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cpp/src/io/csv/csv_gpu.cu

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mhaseeb123 · 2026-11-02T22:35:38Z

+      auto const field_len      = static_cast<size_t>(next_delimiter - field_start);
+      auto const unquoted_field = trim_quotes(field_start, next_delimiter, opts.quotechar);
+      auto const unquoted_len   = static_cast<size_t>(unquoted_field.second - unquoted_field.first);
      if (serialized_trie_contains(opts.trie_na, {field_start, field_len})) {


Quoted NA tokens are missed: "1"\n"NA" infers STRING, pandas gives float64 with a null. is_valid in convert_csv_to_cudf needs the same check.

Suggested change

if (serialized_trie_contains(opts.trie_na, {field_start, field_len})) {

if (serialized_trie_contains(opts.trie_na, {field_start, field_len}) ||

serialized_trie_contains(opts.trie_na, {unquoted_field.first, unquoted_len})) {

mhaseeb123 · 2026-11-02T22:35:38Z

        // Modify field_start & end to ignore whitespace and quotechars
        // This could possibly result in additional empty fields
-        auto const trimmed_field_range = trim_whitespaces_quotes(field_start, next_delimiter);
-        auto const trimmed_field_len   = trimmed_field_range.second - trimmed_field_range.first;
+        // As in seek_field_end, a quote only counts if it opens the field: 5" is not a number
+        auto trimmed_field_range = trim_whitespaces(field_start, next_delimiter);
+        if (trimmed_field_range.first == field_start) {
+          trimmed_field_range =
+            trim_quotes(trimmed_field_range.first, trimmed_field_range.second, opts.quotechar);
+        }
+        auto const trimmed_field_len = trimmed_field_range.second - trimmed_field_range.first;


With the above, no need to re-trim here

Suggested change

// Modify field_start & end to ignore whitespace and quotechars

// This could possibly result in additional empty fields

auto const trimmed_field_range = trim_whitespaces_quotes(field_start, next_delimiter);

auto const trimmed_field_len = trimmed_field_range.second - trimmed_field_range.first;

// As in seek_field_end, a quote only counts if it opens the field: 5" is not a number

auto trimmed_field_range = trim_whitespaces(field_start, next_delimiter);

if (trimmed_field_range.first == field_start) {

trimmed_field_range =

trim_quotes(trimmed_field_range.first, trimmed_field_range.second, opts.quotechar);

}

auto const trimmed_field_len = trimmed_field_range.second - trimmed_field_range.first;

auto const trimmed_field_range = unquoted_field;

auto const trimmed_field_len = unquoted_field.second - unquoted_field.first;

mhaseeb123 · 2026-11-02T22:35:38Z

+  auto const string_type = cudf::data_type{cudf::type_id::STRING};
  cudf::io::csv_reader_options in_opts =
-    cudf::io::csv_reader_options::builder(cudf::io::source_info{in_csv}).header(0);
+    cudf::io::csv_reader_options::builder(cudf::io::source_info{in_csv})
+      .header(0)
+      .dtypes(std::map<std::string, cudf::data_type>{{"Country Code", string_type},
+                                                     {"Area Code", string_type}});


Behavior change: quoted numerics (e.g. zip codes "01234") now silently become ints, as this example shows. CC @vuule

mhaseeb123 · 2026-11-02T22:35:38Z

 }

-TEST_F(CsvReaderTest, StringInference)
+TEST_F(CsvReaderTest, QuotedValuesInference)


nit: Please also cover quoted "NA", "1,000" with .thousands(','), "" with .na_filter(false), and "1"/"true" with .detect_whitespace_around_quotes(true).

mhaseeb123 · 2026-11-03T00:04:07Z

      auto const field_len = static_cast<size_t>(next_delimiter - field_start);
+      auto unquoted_field  = trim_quotes(field_start, next_delimiter, opts.quotechar);
+      if (opts.detect_whitespace_around_quotes) {
+        auto const trimmed  = trim_whitespaces(field_start, next_delimiter);
+        auto const unquoted = trim_quotes(trimmed.first, trimmed.second, opts.quotechar);
+        if (unquoted.first != trimmed.first) { unquoted_field = unquoted; }
+      }
+      auto const unquoted_len = static_cast<size_t>(unquoted_field.second - unquoted_field.first);


Let's trim once here, with the same rule as the numeric path, and reuse it below. Right now "true" (trailing space) infers STRING while "1" infers INT64.

Suggested change

auto const field_len = static_cast<size_t>(next_delimiter - field_start);

auto unquoted_field = trim_quotes(field_start, next_delimiter, opts.quotechar);

if (opts.detect_whitespace_around_quotes) {

auto const trimmed = trim_whitespaces(field_start, next_delimiter);

auto const unquoted = trim_quotes(trimmed.first, trimmed.second, opts.quotechar);

if (unquoted.first != trimmed.first) { unquoted_field = unquoted; }

}

auto const unquoted_len = static_cast<size_t>(unquoted_field.second - unquoted_field.first);

auto const field_len = static_cast<size_t>(next_delimiter - field_start);

// A quote only counts if it opens the field (as in seek_field_end): 5" is not a number

auto unquoted_field = trim_whitespaces(field_start, next_delimiter);

if (opts.detect_whitespace_around_quotes or unquoted_field.first == field_start) {

unquoted_field = trim_quotes(unquoted_field.first, unquoted_field.second, opts.quotechar);

}

auto const unquoted_len = static_cast<size_t>(unquoted_field.second - unquoted_field.first);

vuule · 2026-11-03T04:45:46Z

/ok to test cf6df7c

mhaseeb123 · 2026-11-03T05:06:50Z

pre-commit.ci autofix

mhaseeb123 · 2026-11-03T05:53:07Z

pre-commit.ci autofix

Fix csv quoted value inference

2c4016a

merterbak requested review from a team as code owners November 2, 2026 22:18

merterbak requested review from bdice and mhaseeb123 November 2, 2026 22:18

github-actions Bot assigned merterbak Nov 2, 2026

github-actions Bot added libcudf Affects libcudf (C++/CUDA) code. Python Affects Python cuDF API. cudf.pandas Issues specific to cudf.pandas labels Nov 2, 2026

github-project-automation Bot added this to cuDF Python Nov 2, 2026

github-project-automation Bot moved this to Todo in cuDF Python Nov 2, 2026

Merge branch 'main' into fix-csv-quoted-type-inference

3f1602e

coderabbitai Bot reviewed Nov 2, 2026

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Comment thread cpp/src/io/csv/csv_gpu.cu Resolved

Fix inference for spaced quoted values

f8d514f

coderabbitai Bot reviewed Nov 2, 2026

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Fix bool and inf spaced quote inference

9bed7ff

coderabbitai Bot reviewed Nov 2, 2026

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mhaseeb123 reviewed Nov 3, 2026

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mhaseeb123 requested a review from vuule November 3, 2026 00:10

Merge branch 'main' into fix-csv-quoted-type-inference

cf6df7c

github-actions Bot assigned vuule Nov 3, 2026

mhaseeb123 added bug Something isn't working non-breaking Non-breaking change labels Nov 3, 2026

	if (serialized_trie_contains(opts.trie_na, {field_start, field_len})) {
	if (serialized_trie_contains(opts.trie_na, {field_start, field_len}) \|\|
	serialized_trie_contains(opts.trie_na, {unquoted_field.first, unquoted_len})) {

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