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lancedb/docs/web/snippets/function.mdx
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Brendan Clement 6389784dde docs: apply a registered Function version in the Function guide
The guide applied the local decorated callable to `table["value"]`, which
raises TypeError: a table is not subscriptable, and add_columns takes an
application of a registered version, not the callable's result.

The guide now walks one example from definition to filled column: define
`double`, call it locally, connect to Enterprise, create a table whose
`value` column matches the parameter's type and nullability, register the
function, apply `version(value=col("value"))`, refresh, wait, and read the
values back. Its snippets come from docs/web-tests/py/test_function.py.

The local tests in that file check what `@udf` sends for registration, how
a registered version binds a column, and that a local connection refuses
both registration and Function columns. The Enterprise walkthrough runs
only when LANCEDB_URI, LANCEDB_API_KEY and LANCEDB_HOST_OVERRIDE are set.

The page also stops promising that a retry after a failed refresh costs
only the unfinished rows.
2026-10-05 13:27:53 -07:00

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{/* Auto-generated by scripts/mdx_snippets_gen.py. Do not edit manually. */}
export const PyFunctionApply = "from lancedb import col\n\ntable.add_columns({\"doubled\": version(value=col(\"value\"))})\n";
export const PyFunctionConnect = "import os\n\nimport lancedb\n\ndb = lancedb.connect(\n uri=os.environ[\"LANCEDB_URI\"], # db://your-database\n api_key=os.environ[\"LANCEDB_API_KEY\"],\n region=os.environ.get(\"LANCEDB_REGION\", \"us-east-1\"),\n host_override=os.environ[\"LANCEDB_HOST_OVERRIDE\"],\n)\n";
export const PyFunctionCreateTable = "import pyarrow as pa\n\nschema = pa.schema([pa.field(\"value\", pa.float64(), nullable=False)])\ntable = db.create_table(\n \"function_demo\",\n [{\"value\": 1.0}, {\"value\": 2.0}, {\"value\": 3.0}],\n schema=schema,\n mode=\"overwrite\",\n)\n";
export const PyFunctionDefine = "from lancedb import udf\n\n\n@udf\ndef double(value: float) -> float:\n return value * 2\n";
export const PyFunctionInspect = "rows = table.search().select([\"value\", \"doubled\"]).to_list()\nprint(sorted((row[\"value\"], row[\"doubled\"]) for row in rows))\n# [(1.0, 2.0), (2.0, 4.0), (3.0, 6.0)]\n";
export const PyFunctionLocalCall = "print(double(1.5))\n# 3.0\n";
export const PyFunctionRefresh = "refresh = table.refresh_column_async(\"doubled\")\nresult = refresh.wait()\nprint(result.rows_assigned)\n# 3\n";
export const PyFunctionRegister = "job = db.create_function_async(double)\nversion = job.wait()\n";