[TEPHRA-131] NPE on rollback of a family delete with ConflictDetection.ROW

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 0.6.3
• Labels: phoenix
• Assignee: Gokul Gunasekaran
• Reporter: James R. Taylor
• Created: 25/Sep/15 23:47
• Updated: 02/Nov/15 19:55
• Resolved: 02/Nov/15 19:55

Description

An NPE occurs when attempting to rollback a transaction in which a family delete occurs with a ConflictDetection.ROW. This happens because the ActionChange is not capturing the familyName in this code:

  private Delete transactionalizeAction(Delete delete) throws IOException {
    long transactionTimestamp = tx.getWritePointer();

    byte[] deleteRow = delete.getRow();
    Delete txDelete = new Delete(deleteRow, transactionTimestamp);

    Map<byte[], List<Cell>> familyToDelete = delete.getFamilyCellMap();
    if (familyToDelete.isEmpty()) {
      // perform a row delete is we are using row-level conflict detection
      if (conflictLevel == TxConstants.ConflictDetection.ROW ||
          conflictLevel == TxConstants.ConflictDetection.NONE) {
        // no need to identify individual columns deleted
        addToChangeSet(deleteRow, null, null);  // FIXME (will lead to NPE)
      } else {
        Result result = get(new Get(delete.getRow()));
        // Delete everything
        NavigableMap<byte[], NavigableMap<byte[], byte[]>> resultMap = result.getNoVersionMap();
        for (Map.Entry<byte[], NavigableMap<byte[], byte[]>> familyEntry : resultMap.entrySet()) {
          NavigableMap<byte[], byte[]> familyColumns = result.getFamilyMap(familyEntry.getKey());
          for (Map.Entry<byte[], byte[]> column : familyColumns.entrySet()) {
            txDelete.deleteColumns(familyEntry.getKey(), column.getKey(), transactionTimestamp);
            addToChangeSet(deleteRow, familyEntry.getKey(), column.getKey());
          }
        }
      }
    } else {
      for (Map.Entry<byte [], List<Cell>> familyEntry : familyToDelete.entrySet()) {
        byte[] family = familyEntry.getKey();
        List<Cell> entries = familyEntry.getValue();
        boolean isFamilyDelete = false;
        if (entries.size() == 1) {
          Cell cell = entries.get(0);
          isFamilyDelete = CellUtil.isDeleteFamily(cell);
        }
        if (isFamilyDelete) {
          if (conflictLevel == TxConstants.ConflictDetection.ROW ||
              conflictLevel == TxConstants.ConflictDetection.NONE) {
            // no need to identify individual columns deleted
            txDelete.deleteFamily(family);
            addToChangeSet(deleteRow, null, null);  // FIXME
          } else {

Then when the rollback occurs in the code below, an NPE will occur because the ActionChange has a null familyName:

  @Override
  protected boolean doRollback() throws Exception {
    try {
      // pre-size arraylist of deletes
      int size = 0;
      for (Set<ActionChange> cs : changeSets.values()) {
        size += cs.size();
      }
      List<Delete> rollbackDeletes = new ArrayList<Delete>(size);
      for (Map.Entry<Long, Set<ActionChange>> entry : changeSets.entrySet()) {
        long transactionTimestamp = entry.getKey();
        for (ActionChange change : entry.getValue()) {
          byte[] row = change.getRow();
          byte[] family = change.getFamily();
          byte[] qualifier = change.getQualifier();
          Delete rollbackDelete = new Delete(row);
          rollbackDelete.setAttribute(TxConstants.TX_ROLLBACK_ATTRIBUTE_KEY, new byte[0]);
          switch (conflictLevel) {
            case ROW:
            case NONE:
              // issue family delete for the tx write pointer
              rollbackDelete.deleteFamilyVersion(change.getFamily(), transactionTimestamp);  // NPE will occur here

Not sure how you want to handle the case when familyToDelete.isEmpty() is true (i.e. a row delete - see first FIXME above). Maybe lookup the column families? FWIW, Phoenix will only do family deletes, so we wouldn't hit that code path.