[IMPALA-7923] DecimalValue should be marked as packed

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 3.1.0
• Component/s: Backend
• Target Version: Product Backlog
• Epic Color: ghx-label-7
• Assignee: Daniel Becker
• Reporter: Tim Armstrong
• Created: 04/Dec/18 04:04
• Updated: 09/Jul/20 08:36
• Resolved: 09/Jul/20 08:36

Description

IMPALA-7473 was a symptom of a more general problem that DecimalValue is not guaranteed to be aligned by the Impala runtime, but the class is not marked as packed and, under some circumstances, GCC will emit code for aligned loads to value_ when value_ is an int128.

Testing helps confirm that the compiler does not emit the problematic loads in practice, but it would be better to mark the struct as packed.

Issue Links

• fixes: IMPALA-9111 Sorting 'Decimal16Value's with codegen enabled but codegen optimizations disabled fails
• relates to: IMPALA-7473 RawValue::PrintValue() hits general protection fault with VLOG level 3