[HIVE-14431] Recognize COALESCE as CASE

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 2.2.0
• Fix Version/s: 4.0.0-alpha-1
• Component/s: CBO
• Assignee: Jesús Camacho Rodríguez
• Reporter: Jesús Camacho Rodríguez
• Created: 04/Aug/16 19:35
• Updated: 27/Feb/24 22:23
• Resolved: 07/Oct/18 15:25

Description

Transform:

(COALESCE(a, '')  = '') OR
           (a = 'A' AND b = c)  OR
           (a = 'B' AND b = d) OR
           (a = 'C' AND b = e) OR
           (a = 'D' AND b = f) OR
           (a = 'E' AND b = g) OR
           (a = 'F' AND b = h)

into:

(a='') OR
           (a is null) OR
           (a = 'A' AND b = c)  OR
           (a = 'B' AND b = d) OR
           (a = 'C' AND b = e) OR
           (a = 'D' AND b = f) OR
           (a = 'E' AND b = g) OR
           (a = 'F' AND b = h)

With complex queries, this will lead us to factor more predicates that could be pushed to the TS.

Issue Links

• is blocked by: HIVE-20563 Vectorization: CASE WHEN expression fails when THEN/ELSE type and result type are different