[Proposal] Real-time wide table join

[xuanyu66]

Problem

Currently, Flink doesn't support the statement INSERT ... ON DUPLICATE KEY UPDATE.
It is a common requirement that updates some fields based on the primary key in the Materialized View scenario.

Solution

• Use SQL hints to Achieve semantics INSERT ... ON DUPLICATE KEY UPDATE.
• Prune column to get the needed columns
• Use InsertOrDuplicateKeyUpdateOutputFormat to generate statement INSERT ... ON DUPLICATE KEY UPDATE and batch execute them in TiDB.

Design

#198

Implement

#196

Test

#196

Doc

#196