[IMPALA-5559] Frontend and backend have different notions of which slots are var-len.

• Type: Improvement
• Status: Resolved
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: Impala 2.10.0
• Component/s: Frontend
• Labels: resource-management
• Target Version: Impala 2.10.0
• Epic Color: ghx-label-9
• Assignee: Tim Armstrong
• Reporter: Tim Armstrong
• Created: 22/Jun/17 17:22
• Updated: 30/Jun/17 23:14
• Resolved: 30/Jun/17 23:14

Description

I discovered this on my buffer pool dev branch because the planner miscomputed the amount of reservation required for the sorter on this query:

select t1.cl, COUNT(1) FROM chars_tiny t1 GROUP BY 1 ORDER BY t1.cl

The frontend thinks that it doesn't need var-len data blocks to store t1.cl, which is a large CHAR() column.

I think the problem is that two different concepts are being confused in the code:

• Is the amount of storage required for the slot always a fixed amount?
• Does the slot store data out-of-line from the main tuple?

Issue Links

• is related to: IMPALA-5560 Consider always storing CHAR() slots inline