Support Merge Hint for CTE Inline

[dayicklp]

Development Task

The current version of Common Table Expression (CTE) can not be well applied in MPP, especially can not automatically expand the calculation, which hinders the execution efficiency under TiFlash.

We need to expand CTE to be more compatible with TiFlash and make CTE more widely used in OLAP.

Tech Design

Weekly Report

Test doc

Milestones

Stage

• Inline function, Hint design, Function test(no binding test inside) planner: add a hint for CTE #34574
• add binding and recursive test for Merge hint planner: add binding and recursive test for Merge hint #36352
• fixe Merge hint in nested CTE planner: Fixed Merge hint in nested CTE #36432

Doc

• Add Document for Merge hint planner: update the doc for merge hint docs-cn#10373

Future optimization

• Hints cannot be used after inline (Inl_join hint) Inl_join hints doesn't work when join operator including CTE after merge #35318
• Automatically inline CTE if it has only 1 consumer Planner should automatically inline CTE if it has only 1 consumer #36295
• In multi-loop nested CTE, subsequent queries cannot be executed Merge hint will cause the CTE query to be unrecognized #36373
• Add a system variable to control Add a system variable to control whether to inline CTE or not #36514

[dayicklp]

/cc @winoros

[xiongjiwei]

/assign @dayicklp

[dayicklp]

Following work will be a separate issue