René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"first_value doesn't work when applied to window function output","articleBody":"**Describe the bug**\nA clear and concise description of what the bug is.\nIf I generate a column based on a window function then try to filter and select the first value it barfs\n\n**To Reproduce**\nSteps to reproduce the behavior:\n```python\nimport datafusion as dfn\nfrom datafusion import lit, col, functions as F\nfrom datafusion.expr import Window, WindowFrame\n\ndef main() -\u003e None:\n    ctx = dfn.SessionContext()\n    df = ctx.from_pydict(\n        {\"any_row\": list(range(10))},\n    )\n    df = df.select(\n        \"any_row\",\n        lit(1).alias(\"ones\"),\n    )\n    df = df.select(\n        \"any_row\",\n        F.sum(col(\"ones\"))\\\n            .over(Window(window_frame=WindowFrame(\"rows\", None, 0), order_by=col(\"any_row\").sort(ascending=True))) \\\n            .alias(\"forward_row_sum\"),\n        F.sum(col(\"ones\"))\\\n            .over(Window(window_frame=WindowFrame(\"rows\", None, 0), order_by=col(\"any_row\").sort(ascending=False))) \\\n            .alias(\"reverse_row_sum\"),\n    )\n    df.collect()\n    df.select(\n        F.first_value(col(\"forward_row_sum\"), order_by=col(\"any_row\"))\n    ).collect()\n\n    df.select(\n        F.last_value(col(\"reverse_row_sum\"), filter=col(\"reverse_row_sum\") \u003e= 5, order_by=col(\"any_row\").sort(ascending=True))\n    ).collect()\n\nif __name__ == \"__main__\":\n    main()\n```\n\n```console\nTraceback (most recent call last):\n  File \"/Users/nick/repos/bug.py\", line 39, in \u003cmodule\u003e\n    main()\n    ~~~~^^\n  File \"/Users/nick/repos/bug.py\", line 26, in main\n    ).collect()\n      ~~~~~~~^^\n  File \"/Users/nick/repos/.venv/lib/python3.13/site-packages/datafusion/dataframe.py\", line 681, in collect\n    return self.df.collect()\n           ~~~~~~~~~~~~~~~^^\nException: DataFusion error: NotImplemented(\"Physical plan does not support logical expression AggregateFunction(AggregateFunction { func: AggregateUDF { inner: FirstValue { name: \\\"first_value\\\", signature: Signature { type_signature: Any(1), volatility: Immutable }, accumulator: \\\"\u003cFUNC\u003e\\\" } }, params: AggregateFunctionParams { args: [Column(Column { relation: None, name: \\\"sum(ones) ORDER BY [c19e557aec20e49b985bb070e969ba68f.any_row ASC NULLS FIRST] ROWS BETWEEN UNBOUNDED PRECEDING AND 0 FOLLOWING\\\" })], distinct: false, filter: None, order_by: [Sort { expr: Column(Column { relation: Some(Bare { table: \\\"c19e557aec20e49b985bb070e969ba68f\\\" }), name: \\\"any_row\\\" }), asc: true, nulls_first: true }], null_treatment: Some(RespectNulls) } })\")\n```\n\n**Expected behavior**\nA clear and concise description of what you expected to happen.\nThat I get the first (or last) value.\n\n**Additional context**\nAdd any other context about the problem here.\n```python\nimport datafusion as dfn\n\u003e\u003e\u003e dfn.__version__\n'50.1.0'\n```","author":{"url":"https://github.com/ntjohnson1","@type":"Person","name":"ntjohnson1"},"datePublished":"2025-11-05T20:22:38.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":5},"url":"https://github.com/1300/datafusion-python/issues/1300"}