ARCHIVED TRAINING / narwhals-dev/narwhals
narwhals-dev__narwhals-1679
This is a preserved training example. Membership in the current training wave has not been verified.
Problem statement
bug: `is_duplicated` returns wrong number of elements for pyarrow
```python
import pandas as pd
import polars as pl
import pyarrow as pa
import narwhals as nw
df = pa.table({'a': [1, None, 1, None, 2, 3]})
print(nw.from_native(df).select(nw.col('a').is_duplicated()).to_native())
df = pl.DataFrame({'a': [1, None, 1, None, 2, 3]})
print(nw.from_native(df).select(nw.col('a').is_duplicated()).to_native())
df = pd.DataFrame({'a': [1, None, 1, None, 2, 3]})
print(nw.from_native(df).select(nw.col('a').is_duplicated()).to_native())
```
```
pyarrow.Table
a: bool
----
a: [[true,true,false,false]]
shape: (6, 1)
┌───────┐
│ a │
│ --- │
│ bool │
╞═══════╡
│ true │
│ true │
│ true │
│ true │
│ false │
│ false │
└───────┘
a
0 True
1 True
2 True
3 True
4 False
5 False
```
The last one has fewer elements
## Hints:
MarcoGorelli: awesome, thanks @FBruzzesi for your extra commit and review!
Training membership
opd_e4b_pure_v6b
Task issues extracted from preserved verified_rft_messages training examples. This is not a verified current RL wave manifest.
Task and snapshot provenance
Snapshot captured 2026-11-12T17:06:59.476467+00:00 · Autoresearch-Arena/gemma-4-developer-agent
{
"datasets": [
"opd_e4b_pure_v6b"
],
"examples": 3,
"instance_id": "narwhals-dev__narwhals-1679",
"problem_statement": "bug: `is_duplicated` returns wrong number of elements for pyarrow\n```python\r\nimport pandas as pd\r\nimport polars as pl\r\nimport pyarrow as pa\r\nimport narwhals as nw\r\n\r\ndf = pa.table({'a': [1, None, 1, None, 2, 3]})\r\nprint(nw.from_native(df).select(nw.col('a').is_duplicated()).to_native())\r\ndf = pl.DataFrame({'a': [1, None, 1, None, 2, 3]})\r\nprint(nw.from_native(df).select(nw.col('a').is_duplicated()).to_native())\r\ndf = pd.DataFrame({'a': [1, None, 1, None, 2, 3]})\r\nprint(nw.from_native(df).select(nw.col('a').is_duplicated()).to_native())\r\n```\r\n\r\n```\r\npyarrow.Table\r\na: bool\r\n----\r\na: [[true,true,false,false]]\r\nshape: (6, 1)\r\n┌───────┐\r\n│ a │\r\n│ --- │\r\n│ bool │\r\n╞═══════╡\r\n│ true │\r\n│ true │\r\n│ true │\r\n│ true │\r\n│ false │\r\n│ false │\r\n└───────┘\r\n a\r\n0 True\r\n1 True\r\n2 True\r\n3 True\r\n4 False\r\n5 False\r\n```\r\n\r\nThe last one has fewer elements\n\n## Hints:\nMarcoGorelli: awesome, thanks @FBruzzesi for your extra commit and review!",
"repo": "narwhals-dev/narwhals",
"source": "v2/experiments/train_data/opd_e4b_pure_v6b/verified_rft_messages.jsonl",
"source_sha256": "0f62460a9706eea5e1605255896f191ab00cb5706c5f1f2e1c293e9a718218dc"
}{
"captured_at": "2026-11-12T17:06:59.476467+00:00",
"membership": "archived training",
"membership_evidence": "Task issues extracted from preserved verified_rft_messages training examples. This is not a verified current RL wave manifest.",
"name": "Preserved post-training task archive",
"source": "Autoresearch-Arena/gemma-4-developer-agent",
"source_revision": "016496de222aaafca0d4ee4c18efc63ba616f76e",
"sources": [
{
"path": "v2/experiments/train_data/opd_e4b_cispo_v5/verified_rft_messages.jsonl",
"sha256": "a43610ad0dfb6ace95375cfae09000f41afc0338cc925af870a4ade7a9b20c4c"
},
{
"path": "v2/experiments/train_data/opd_e4b_hybrid_v3/verified_rft_messages.jsonl",
"sha256": "bd326303eb127e8e5e08f03daf97bb88d79d19709d59f3f93f348bc56686a8df"
},
{
"path": "v2/experiments/train_data/opd_e4b_onpolicy_v3/verified_rft_messages.jsonl",
"sha256": "960c680e797e823a0d3a22f4b1d5ef60a72971373d703b877340b0c9126aaf68"
},
{
"path": "v2/experiments/train_data/opd_e4b_pure_v6a/verified_rft_messages.jsonl",
"sha256": "f045b7ca5b3883a1e2eaee81e1c02a4a1b53dd7b7b36e98bacb2ba5823a15148"
},
{
"path": "v2/experiments/train_data/opd_e4b_pure_v6b/verified_rft_messages.jsonl",
"sha256": "0f62460a9706eea5e1605255896f191ab00cb5706c5f1f2e1c293e9a718218dc"
},
{
"path": "v2/experiments/train_data/opd_e4b_pure_v7/verified_rft_messages.jsonl",
"sha256": "e37f7bd675322f3f81500b73559d60d5f602ca0537bf19f5cb06332c728c7b72"
},
{
"path": "v2/experiments/train_data/opd_e4b_pure_v7b/verified_rft_messages.jsonl",
"sha256": "b864bdc8695183433eef6e31cb8d33fad44ba3aded2170c1ade4ad5b2944ce23"
},
{
"path": "v2/experiments/train_data/opd_e4b_self_audit_v4/verified_rft_messages.jsonl",
"sha256": "0026023745afb8f3dc1c176dc7f7171157b4ad5a66656b524af218e8e19ceee6"
},
{
"path": "v2/experiments/train_data/rft_e4b_aligned_v2/verified_rft_messages.jsonl",
"sha256": "92a4515fee9d152b0d4c510ee3ce4caaaffe2003ba7584469f8027f174aab18c"
},
{
"path": "v2/experiments/train_data/rft_v1/verified_rft_messages.jsonl",
"sha256": "a42453ccd7ac7680b0a03865e8e7080bc8bf74c8d9d193b440c441ed46f8512b"
},
{
"path": "v2/experiments/train_data/rft_v2/verified_rft_messages.jsonl",
"sha256": "18f4b3bd7e651f83c6acab479c9475e3fa50dc652a384f309e97146983ac85ba"
}
]
}