title: Very, very slow write from dataframe to SQL Server table
body: <p>I'm running the code below and it works fine, but it's supper, super, super slow.</p>
  
  <pre><code>df.write.format('jdbc').options(url='jdbc:sqlserver://server_name.database.windows.net:1433;databaseName=db_name', 
                               dbtable='dbo.my_table', 
                               user='usr', 
                               password='pwd', 
                               batchsize=500000).mode('append').save()
  </code></pre>
  
  <p>I thought it would load records in batches of 500k at a time, but when I run the code and do record counts in SQL Server after the job kicks off, it's updating about 50 records per second.  Hopefully there is an easy fix for this.  Thanks!</p>