[IMPALA-5532] Don't heap-allocate compressor objects in RowBatch

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Affects Version/s: Impala 2.10.0
• Fix Version/s: Impala 2.10.0
• Component/s: Backend
• Epic Color: ghx-label-4
• Assignee: Henry Robinson
• Reporter: Henry Robinson
• Created: 19/Jun/17 18:28
• Updated: 24/Jul/17 15:58
• Resolved: 24/Jul/17 15:58

Description

Every call to RowBatch::RowBatch(..., const TRowBatch&, ...) or RowBatch::Serialize() creates a (de)compressor object. That uses the Codec::CreateCompressor() interface which returns a pointer to a Codec object, so that the virtual compression interface can be used.

However, we always use LZ4 compression, and so needlessly heap-allocate the compressor objects to get the advantage of implementation hiding which we don't actually need. We should just declare a stack-allocated LZ4 (de)compressor when needed.