[IMPALA-6080] Clean up descriptor table handling in coordinator

• Type: Improvement
• Status: Resolved
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: Impala 2.11.0
• Component/s: Backend
• Target Version: Product Backlog
• Epic Color: ghx-label-4
• Assignee: Tim Armstrong
• Reporter: Tim Armstrong
• Created: 18/Oct/17 23:53
• Updated: 16/Nov/17 22:12
• Resolved: 16/Nov/17 22:12

Description

One of the parts of this patch https://gerrit.cloudera.org/#/c/7065/ was cleanup of how descriptor tables were managed. As described in the commit message:

Also: 
- adds DescriptorTbl::CreateHdfsTableDescriptor to avoid having to create an entire DescriptorTbl during INSERT finalization (when only a descriptor for the output table is needed) - removes TQueryExecRequest.desc_tbl, there's already a home for it in TQueryContext.desc_tbl

That cleanup should be independent of the larger patch so we could get it in separately.