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  1. Debezium
  2. DBZ-7068

Oracle events can be emitted out of order when LOB enabled

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Details

    • Bug
    • Resolution: Duplicate
    • Critical
    • None
    • 2.3.4.Final, 2.4.0.Final
    • oracle-connector
    • None
    • False
    • None
    • False

    Description

      When enabling LOB support within the Oracle connector, there are use cases where the TransactionCommitConsumer will immediately dispatch a row when no LOB columns are detected and this will cause the events to be dispatched out of chronological order.

      This regression was introduced by DBZ-6107.

      Given use case:

      connection.executeWithoutCommitting("INSERT INTO addresses (ID,PERSON_ID) values (" + i + ",-1)");      //  i addresses         accum=null
      connection.executeWithoutCommitting("UPDATE email SET person_id = " + i + " WHERE id = -1");            // -1 email             accum=null
      connection.executeWithoutCommitting("INSERT INTO email (ID,PERSON_ID) values (" + i + ",-1)");          //  i email             accum=null
      connection.executeWithoutCommitting("UPDATE email SET person_id = " + (i + 999) + " WHERE id = " + i);  //  i email (Folded)    accum has value
      connection.executeWithoutCommitting("UPDATE email SET person_id = " + (i + 1000) + " WHERE id = -1");   // -1 email             accum has value, EMAIL has no LOB columns - so released
      connection.executeWithoutCommitting("UPDATE phone SET person_id = " + i + " WHERE id = -1");            // -1 phone             accum=null
      connection.executeWithoutCommitting("INSERT INTO phone (ID,PERSON_ID) values (" + i + ",-1)");          //  i phone             accum=null
      connection.executeWithoutCommitting("UPDATE phone SET person_id = " + i + " WHERE id = " + i);          //  i phone (Folded)    accum has value
      connection.executeWithoutCommitting("UPDATE phone SET person_id = -1 WHERE id = -1");                   // -1 phone             accum has value, PHONE has no LOB columns - so released
      connection.executeWithoutCommitting("UPDATE addresses SET person_id = " + i + " WHERE id = -1");        // -1 addresses         accum=null
      

      We can see there are two situations where the AccumulatorEvent has a value but the consumer immediately dispatches the events. This leads to a chronological order problem:

      // UPDATE 7558821 PHONE (RELEASED)
      // UPDATE 7558818 EMAIL (RELEASED)
      // INSERT 7558815 ADDRESSES
      // INSERT 7558818 EMAIL
      // UPDATE 7558818 EMAIL
      // INSERT 7558821 PHONE
      // UPDATE 7558821 PHONE
      // UPDATE 7558825 ADDRESSES
      

      In addition, none of these tables have LOB columns, so technically the outcome should be 10 events, not 8 as well.

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              ccranfor@redhat.com Chris Cranford
              ccranfor@redhat.com Chris Cranford
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                Updated:
                Resolved: