I tested the pull request and it allowed Vertica queries to execute in parallel with one modification. Thanks!

I had to comment:
// if (statement.isClosed()) {
// connection = getConnection(propertyKey);
// statement = connection.createStatement();
// }
since I ran into:
java.lang.AbstractMethodError: com.vertica.jdbc.VerticaStatementImpl.isClosed()Z
at org.apache.zeppelin.hive.HiveInterpreter.getStatement(HiveInterpreter.java:208)

Can you help me understand the need for the statement.isClosed() check in line 208 since the statement is created in line 207?

It's soft of defensive code for avoiding error. Do you think it's redundant? I'll fix this code more general :-). Thanks for the review quickly.

@praagarw Could you please review this PR again?

Hi Jongyoul, since createStatement is implemented in the JDBC drivers, I think it is unlikely it will return a closed statement. However, I am all for defensive coding and your fix in ZEPPELIN-487 looks good to me.

@praagarw Sure, but I couldn't guarantee all of jdbc connections create statement when it's alive. Thus double check might be helpful in that case. And thanks for kind review. I'm merging in three day.

Merging without additional discussion