title: Which characters are allowed in a BigQuery STRING column (getting "UDF out of memory" error)
body: <p>I have a dataframe containing receipt-data. The column <code>text</code> in my dataframe contains the text from the receipt and seems to be an issue when I try to upload the data to BigQuery using <code>df.to_gbq(...)</code> since it produces the error</p>
  <pre><code>GenericGBQException: Reason: 400 Resources exceeded during query execution: UDF out of memory.; Failed to read Parquet file /some/file. 
  This might happen if the file contains a row that is too large,
   or if the total size of the pages loaded for the queried columns is too large.
  </code></pre>
  <p>According to the error-message it seems to be an &quot;memory error&quot;, but I have tried to convert all characters in each text to an &quot;a&quot; (to see if the strings contained to many characters) but that worked fine i.e I doubt it is that.</p>
  <p>I have tried converting all characters to <code>utf8</code> by</p>
  <p><code>df[&quot;text&quot;] = df[&quot;text&quot;].str.encode('utf-8')</code> (since according to the <a href="https://cloud.google.com/bigquery/docs/reference/standard-sql/lexical" rel="nofollow noreferrer">docs</a> they should be so) but that failed. I have tried to replace &quot;\n&quot; with &quot; &quot; but that fails aswell.</p>
  <p>It seems like there's some values in my receipt-text that causes some troubles, but It's very difficult to figure out what (and since I have ~3 mio rows, it takes a while to try each and every row at a time) - are there any values that are not allowed in a big-query table?</p>