title: DatabaseError: Write pandas dataframe to vertica using to_sql and vertica_python
body: <p>I have a simple dataframe like this</p>
  
  <pre><code>df = pd.DataFrame({"A":[1, 2, 3], "B":["a", "b", "c"]})
  </code></pre>
  
  <p>I would like to write this dataframe to vertica database using to_sql method.  So I use vertica_python module and my code is the following</p>
  
  <pre><code>import pandas as pd
  import vertica_python
  
  cxn = {"user":'myuser',
         "password":'mypassword',
         "host":'xx.x.x.xx',
         "port":yyyy,
         "database":"mydb"}
  
  engine = vertica_python.connect(**cxn)
  
  df = pd.DataFrame({"A":[1, 2, 3], "B":["a", "b", "c"]})
  
  df.to_sql("df", index=False, if_exists="replace", con=engine, schema="public", dtype={"A":"int", "B":"int"})
  </code></pre>
  
  <p>Then i got database error which i could not fix it as follows.</p>
  
  <pre><code>DatabaseError: Execution failed on sql 'SELECT name FROM sqlite_master WHERE type='table' AND name=?;': not all arguments converted during string formatting
  </code></pre>
  
  <p>May I have your suggestions how to solve this problem? Thank you very much.</p>