[IMPALA-12377] Improve count star performance for external data source

• Type: Sub-task
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Impala 4.4.0
• Component/s: Backend, Frontend
• Epic Color: ghx-label-13
• Assignee: Wenzhe Zhou
• Reporter: Wenzhe Zhou
• Created: 17/Aug/23 18:34
• Updated: 14/Nov/23 04:53
• Resolved: 14/Nov/23 04:53

Description

The code to handle count query in backend function DataSourceScanNode::GetNext() are not efficient. Even there are no column data returned from external data source, it still try to materialize rows and add rows to RowBatch one by one up to the number of row count. It also call GetNextInputBatch() multiple times (count / batch_size), while GetNextInputBatch() invoke JNI function.