feat: produce metadata in optimizer output

[yliang412]

Closes #65. This PR produces metadata in optimizer output. Currently, the only metadata kept is the group id. The group id information has the following benefits:

• allow the consumer of the optd plan to recover reusable fragments in the DAG-shaped query plan.
• implement adaptive physical collector outside optd-core.
• display cardinality cost: Display cardinality and cost in explain #89

Looking forward to feedbacks!

In the example below, we produce the same plan as before when adaptiveness is enabled.

❯ create table t1(t1v1 int, t1v2 int);
0 rows in set. Query took 0.009 seconds.

Execution took 0.000 secs, Planning took 0.000 secs
❯ explain select * from t1 as a, t1 as b;
+--------------------------------------------------+-------------------------------------------------------------------------------------------------+
| plan_type                                        | plan                                                                                            |
+--------------------------------------------------+-------------------------------------------------------------------------------------------------+
| logical_plan after datafusion                    | Projection: a.t1v1, a.t1v2, b.t1v1, b.t1v2                                                      |
|                                                  |   CrossJoin:                                                                                    |
|                                                  |     SubqueryAlias: a                                                                            |
|                                                  |       TableScan: t1                                                                             |
|                                                  |     SubqueryAlias: b                                                                            |
|                                                  |       TableScan: t1                                                                             |
| logical_plan after optd                          | LogicalProjection { exprs: [ #0, #1, #2, #3 ] }                                                 |
|                                                  | └── LogicalJoin { join_type: Cross, cond: true }                                                |
|                                                  |     ├── LogicalScan { table: t1 }                                                               |
|                                                  |     └── LogicalScan { table: t1 }                                                               |
| physical_plan after optd                         | PhysicalProjection { exprs: [ #0, #1, #2, #3 ] }                                                |
|                                                  | └── PhysicalNestedLoopJoin { join_type: Cross, cond: true }                                     |
|                                                  |     ├── PhysicalScan { table: t1 }                                                              |
|                                                  |     └── PhysicalScan { table: t1 }                                                              |
| physical_plan after optd-join-order              | (NLJ t1 t1)                                                                                     |
| physical_plan after optd-all-join-orders         | SAME TEXT AS ABOVE                                                                              |
| physical_plan after optd-all-logical-join-orders | (Join t1 t1)                                                                                    |
| physical_plan                                    | CollectorExec group_id=!17                                                                      |
|                                                  |   ProjectionExec: expr=[<expr>@0 as col0, <expr>@1 as col1, <expr>@2 as col2, <expr>@3 as col3] |
|                                                  |     CollectorExec group_id=!5                                                                   |
|                                                  |       CrossJoinExec                                                                             |
|                                                  |         CollectorExec group_id=!1                                                               |
|                                                  |           MemoryExec: partitions=1, partition_sizes=[0]                                         |
|                                                  |         CollectorExec group_id=!1                                                               |
|                                                  |           MemoryExec: partitions=1, partition_sizes=[0]                                         |
|                                                  |                                                                                                 |
+--------------------------------------------------+-------------------------------------------------------------------------------------------------+

[Gun9niR]

Do we still need this? Maintaining two versions of step_get_optimizer_rel_[with_meta] seems error-prone.

[yliang412]

Yea maybe I will add an Option<Meta> and keep one copy.

[Gun9niR]

When will this meta be none though?

[yliang412]

You are right, I think I was mixing this one up with memo.get_best_group_binding().

[Gun9niR]

This feature is great! IIUC it also enables displaying logical properties or cost in explain stmt.

[Gun9niR]

lgtm