Re: ORA-8177 with Hive transactions

[Sergey Shelukhin]

There’s HIVE-11831<https://issues.apache.org/jira/browse/HIVE-11831> and 
https://issues.apache.org/jira/browse/HIVE-11833 that try to address this.
We can do a patch similar to the first one; can you file a JIRA?

From: Steve Howard <stevedhow...@gmail.com<mailto:stevedhow...@gmail.com>>
Reply-To: "user@hive.apache.org<mailto:user@hive.apache.org>" 
<user@hive.apache.org<mailto:user@hive.apache.org>>
Date: Friday, September 18, 2015 at 10:54
To: "user@hive.apache.org<mailto:user@hive.apache.org>" 
<user@hive.apache.org<mailto:user@hive.apache.org>>
Subject: ORA-8177 with Hive transactions

While troubleshooting an issue with transactions shortly after enabling them, I 
noticed the following in an Oracle trace, which is our metastore for hive...

ORA-8177: can't serialize access for this transaction

These were thrown on "insert into HIVE_LOCKS..."

Traditionally in Oracle, if an application actually needs serializable 
transactions, the fix is to to set initrans and maxtrans to the number of 
concurrent writers.  When I ran what is below on a table similar to HIVE_LOCKS, 
this exception was thrown everywhere.  The fix is to recreate the table with 
higher values for initrans (only 1 is the default for initrans, and 255 is the 
default for maxtrans).  When I did this and re-ran what is below, the 
exceptions were no longer thrown.

Does anyone have any feedback on this performance hint?  The exceptions in hive 
are thrown from the checkRetryable method in the TxnHandler class, but I 
couldn't find what class.method throws them.  Perhaps the exceptions are not 
impactful, but given the fact the method expects them as it checks for the 
string in the exception message, I thought I would ask for feedback before we 
recreate the HIVE_LOCKS table with a higher value for INITRANS.


import java.sql.*;public class testLock implements Runnable {
  public static void main (String[] args) throws Exception {
    Class.forName("oracle.jdbc.driver.OracleDriver");
    for (int i = 1; i <= 100; i++) {
      testLock tl = new testLock();
    }
  }

  public testLock() {
    Thread t = new Thread(this);
    t.start();
  }

  public void run() {
    try {
      Connection conn = 
DriverManager.getConnection("jdbc:oracle:thin:username/pwd@dbhost:1521/dbservice");
      conn.createStatement().execute("alter session set isolation_level = 
serializable");
      PreparedStatement pst = conn.prepareStatement("update test set a = ?");
      for (int j = 1; j <= 10000; j++) {
        pst.setInt(1,j);
        pst.execute();
        conn.commit();
        System.out.println("worked");
      }
    }
    catch (Exception e) {
      System.out.println(e.getMessage());
    }
  }}