[KYLIN-2764] Build the dict for UHC column with MR

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: v2.0.0
• Fix Version/s: v2.3.0
• Component/s: Job Engine
• Assignee: Kaisen Kang
• Reporter: Kaisen Kang
• Created: 27/Jul/17 14:01
• Updated: 02/Apr/18 13:42
• Resolved: 23/Oct/17 04:00

Description

KYLIN-2217 has built dict for normal column with MR, but the UHC column still build dict in JobServer. Like KYLIN-2217, we also could use MR build dict for UHC column. which could thoroughly release the memory pressure and improve job concurrent for JobServer as well as speed up multi UHC columns procedure.

The MR input is the output of "Extract Fact Table Distinct Columns", the MR output is the UHC column dict. Because it is very hard build global dict with multi reducers, I use one reducer handle one UHC column and allocate enough memory to the reducer. According to my test, 8G memory is enough.

Issue Links

• causes: KYLIN-3287 When a shard by column is in dict encoding, dict building error.