title: Convert to date in cloud datafusion
body: <p>How do we convert a string to date in cloud datafusion? </p>
  
  <p>I have a column with the value say 20191120 (format of yyyyMMdd) i want to load this into a table in bigquery as date. The table column datatype is also date. </p>
  
  <p>What i have tried so far is that i converted the string to timestamp using "parse-as-simple-date" and i try to convert it to format using format-date to "yyyy-MM-dd", but this step converts it to string and the final load fails. I have even tried to explicitly mention the column as date in the o/p schema as date. But it fails at runtime.</p>
  
  <p>I tried keeping it as timestamp in the pipeline and try loading the date into Bigquery date type.</p>
  
  <p>I noticed in the error that came op was field dt_1 incompatible with avro integer. Is datafusion internally converting the extract into avro before loading. AVRO does not have a date datatype which is causing the isssue?</p>