[FLINK-19639] Support nested push down for SupportsProjectionPushDown interface in planner

• Type: Sub-task
• Status: Closed
• Priority: Major
• Resolution: Implemented
• Fix Version/s: 1.12.0
• Component/s: Table SQL / Planner
• Labels: pull-request-available
• Assignee: Shengkai Fang
• Reporter: Shengkai Fang
• Created: 14/Oct/20 09:30
• Updated: 04/Nov/20 07:37
• Resolved: 04/Nov/20 07:36

Description

Support to push nested projection into TableSourceScan. But it may cause name conflicts in some situaion. For example, we create the table with ddl

CREATE TABLE NestedTable (
     nest1 ROW<a INT>,
     nest2 ROW<a INT>
)

and with query

SELECT nest1.a, nest2.a from NestedTable

and we will get 2 `a` in the new schema when pushing projection.
Here we use '_' to concatenate the names of all levels as the name of the nested fields. In this example, we will get fields nest1_a, nest2_a in the new schema.

Issue Links

• links to: GitHub Pull Request #13631