[IMPALA-6187] Scan with conjuncts but no materialized slots crashes Impalad

• Type: Bug
• Status: Resolved
• Priority: Critical
• Resolution: Fixed
• Affects Version/s: Impala 2.10.0
• Fix Version/s: Impala 2.11.0
• Component/s: Backend
• Labels: correctness
• Target Version: Impala 2.11.0
• Epic Color: ghx-label-2
• Assignee: Michael Ho
• Reporter: Michael Ho
• Due: 22/Nov/17
• Created: 15/Nov/17 23:06
• Updated: 29/Nov/17 07:15
• Resolved: 29/Nov/17 07:15

Description

The simple query

 select count(*) from tpch_parquet.lineitem where rand() = 10.0 

will trigger the following DCHECK below in HdfsScanner::WriteTemplate():

int HdfsScanner::WriteTemplateTuples(TupleRow* row, int num_tuples) {
  DCHECK_GE(num_tuples, 0);
  DCHECK_EQ(scan_node_->tuple_idx(), 0);
  DCHECK_EQ(conjunct_evals_->size(), 0); <<------
  if (num_tuples == 0 || template_tuple_ == NULL) return num_tuples;

  Tuple** row_tuple = reinterpret_cast<Tuple**>(row);
  for (int i = 0; i < num_tuples; ++i) row_tuple[i] = template_tuple_;
  return num_tuples;
}

The assumption in the scanner is that if there are no materialized slots (e.g. count star), there should be no conjuncts too but that doesn't always seems to be the case.