ComputeError: could not append value when creating Polars DataFrame about polars HOT 4 OPEN

What's in your res variable? Please create a reproducible example - without it, we cannot do much.

I can say that you should probably be using read_database or read_database_uri for this, rather than reading stuff into a cursor and plugging it into the DataFrame constructor.

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I created the reproducible example in test.json and updated the issue. The error is still there.

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The problem was solved using by setting infer_schema_length to None, thanks to jqurious

pl.DataFrame(res, infer_schema_length=None)

It seems the error was raised because the default value of infer_schema_length is 100. However, in our data, the type of that column can not be detected until a row is bigger than 100.

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The error description only suggests increasing the infer_schema_length. Now this error description can be modified:
make sure that all rows have the same schema or consider increasing infer_schema_length or setting infer_schema_length to None. it might also be that a value overflows the data-type's capacity

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