[IMPALA-11107] Allow specifying footer size in HdfsScanner::IssueFooterRanges

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 4.0.0
• Fix Version/s: Impala 4.1.0
• Component/s: Backend
• Epic Link: ORC Performance
• Epic Color: ghx-label-9
• Assignee: Riza Suminto
• Reporter: Riza Suminto
• Created: 03/Feb/22 19:11
• Updated: 13/Feb/22 03:38
• Resolved: 13/Feb/22 03:38

Description

Currently, FOOTER_SIZE is a constant of 100KB in HdfsScanner::IssueFooterRanges:

https://github.com/apache/impala/blob/57982ef/be/src/exec/hdfs-scanner.cc#L832 

Some scanner subclass such as HdfsOrcScanner expect that footer size is much lower at 16KB. We should add footer_size as parameter so different file format can ask for different footer range size.

Having more precise initial range can also help reduce waste in the data cache: 
https://github.com/apache/impala/blob/57982ef/be/src/runtime/io/data-cache.h#L73