Feature Request: Richer SQL Hints

[zz-jason]

Feature Request

Is your feature request related to a problem? Please describe:

The supported SQL Hints are not enough to control the behavior of TiDB SQL Optimizer. We need hints to:

• control whether to choose hash or stream aggregate operator
• control whether to pushdown the aggregate operator to the coprocessor
• ...

Describe the feature you'd like:

A richer sql hint set:

Hint Name	Priority	Status	PR
HASH_AGG	P1	Completed	https://github.com/pingcap/tidb/pull/11364
STREAM_AGG	P1	Completed	https://github.com/pingcap/tidb/pull/11364
USE_INDEX	P1	Completed	https://github.com/pingcap/tidb/pull/11746
IGNORE_INDEX	P1	Completed	https://github.com/pingcap/tidb/pull/12059
AGG_TO_COP	P1	Completed	https://github.com/pingcap/tidb/pull/12043
READ_FROM_STORAGE	P1	Completed	https://github.com/pingcap/tidb/pull/12479
READ_FROM_REPLICA	P1	Completed	https://github.com/pingcap/tidb/pull/11809
USE_INDEX_MERGE	P1	Completed	#12843
NO_INDEX_MERGE	P1	Completed	https://github.com/pingcap/tidb/pull/11809
USE_TOJA	P1	Completed	https://github.com/pingcap/tidb/pull/11809
MEMORY_QUOTA	P1	Completed	https://github.com/pingcap/tidb/pull/11809
QUERY_BLOCK	P1	Completed	https://github.com/pingcap/tidb/pull/11861
ENABLE_PLAN_CACHE	P2
QUERY_TYPE	P2
INL_JOIN	P3	Completed	https://github.com/pingcap/tidb/pull/11673
BNL_JOIN	P3
HASH_JOIN	P3	Completed	https://github.com/pingcap/tidb/pull/11673
SM_JOIN	P3	Completed	https://github.com/pingcap/tidb/pull/11673
USE_PLAN_CACHE	P4

Describe alternatives you've considered:

N/A

Teachability, Documentation, Adoption, Migration Strategy:

N/A

[foreyes]

Status updated.

[zz-jason]

All the P1 hints are added, I think we can close this issue. Once we need the P2 or P3 Hints, we can create a new issue to trace the progress. How do you think? @eurekaka