[IMPALA-11655] Impala should set merge-on-read by default

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: Impala 4.2.0
• Component/s: Frontend
• Labels: impala-iceberg
• Epic Color: ghx-label-12
• Assignee: Zoltán Borók-Nagy
• Reporter: Zoltán Borók-Nagy
• Created: 12/Oct/22 13:03
• Updated: 24/Jul/23 15:14
• Resolved: 24/Jul/23 15:14

Description

Similarly to HIVE-26596 Impala should set merge-on-read delete mode for V2 tables, unless otherwise specified:

• during table creation with 'format-version'='2'
• during alter table set tblproperties 'format-version'='2'

We do so because in the foreseeable future Impala will only support merge-on-read (on the write-side, on the read side copy-on-write is also supported). Also, currently Hive only supports merge-on-read for DELETEs and UPDATEs.