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fix(dagster-polars): load pl.Date columns into BigQuery as DATE - #363
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October 12, 2026 18:37
PolarsBigQueryTypeHandler converted frames with DataFrame.to_pandas(), which casts pl.Date to datetime64, so BigQuery created TIMESTAMP columns. Use date_as_object=True so the BigQuery client infers DATE. Adds the first BigQuery handler tests, including a regression test for this behaviour. Fixes dagster-io#253
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Fixes #253
Summary & Motivation
PolarsBigQueryTypeHandlerconverted frames withDataFrame.to_pandas(), which castspl.Datetodatetime64. BigQuery therefore createdTIMESTAMPcolumns instead ofDATE.to_pandas(date_as_object=True)sopl.Datestays asdatetime.dateand the BigQuery client infersDATE. Datetime and string columns are unchanged.How I Tested These Changes
dagster_polars_tests/test_bigquery.py(first BigQuery handler tests). The regression test mocks the BigQuery client and asserts the schema inferred for the frame passed toload_table_from_dataframe:DATEforpl.Date,TIMESTAMPforpl.Datetime,STRINGfor strings. It fails without the fix and passes with it.ruff check,ruff format --checkandty checkpass. Not tested against a live BigQuery project.Changelog
Entry added to
libraries/dagster-polars/CHANGELOG.md.