Hi there! Im trying to output the result of a software-defined asset to an existing BigQuery table. I use the

BigQueryPandasIOManager

. When the job is going to write to the table it fails because one of the columns in the dataframe is being translated to integer instead of string. This seems to happen because the column in the dataframe is None and dagster by default may infer that the type is an integer. This is the error I get:

google.api_core.exceptions.BadRequest: 400 Provided Schema does not match Table innate-empire-283902:enrichment.person_batch_enrichment_output. Field error_code has changed type from STRING to INTEGER

Is there a way to workaround this? How can I tell dagster that the output type of the column is a string?

Hi @Miguel Caballero Pinto! The bigquery connector that Dagster is using under the hood is just using the type information that's available on the pandas DataFrame object in order to predict what type a column should be translated to. It sounds like you're correct that this is related to the column being None and this guess being incorrect. One option here would be to manually convert the type of your

error_code

column within pandas, i.e.

my_df = ...
my_df.error_code = my_df.error_code.astype(str)

this should ensure that this column is interpreted as a string

Ok! Or maybe specify the

dtype

argument of the dataframe constructor?

yep! that'd work as well