planner,executor: enable plan cache for partition table

[tiancaiamao]

What problem does this PR solve?

Problem Summary:

In the new implementation, queries on the partition table are not converted to UnionScan and partition pruning on in executor builder.
So it is possible to use plan cache for the partition table now.
This PR enables plan cache for the partition table.

What is changed and how it works?

What's Changed:

How it Works:

Revert part of the #16375

Check List

Tests

• Unit test

The old unit test TestPrepareCacheForPartition should cover the changes.

Release note

• Enable prepared plan cache for the partitioned table.

[tiancaiamao]

PTAL @imtbkcat @lysu

[codecov]

Codecov Report

Merging #19124 into master will not change coverage.
The diff coverage is n/a.

@@             Coverage Diff             @@
##             master     #19124   +/-   ##
===========================================
  Coverage   79.1163%   79.1163%           
===========================================
  Files           547        547           
  Lines        148772     148772           
===========================================
  Hits         117703     117703           
  Misses        21606      21606           
  Partials       9463       9463           

[zz-jason]

@eurekaka PTAL

[imtbkcat]

MySQL [test]> explain select * from t where a = 9;
+------------------------+---------+-----------+---------------+---------------------------------------------+
| id                     | estRows | task      | access object | operator info                               |
+------------------------+---------+-----------+---------------+---------------------------------------------+
| TableReader_6          | 1.00    | root      | partition:p0  | data:TableRangeScan_5                       |
| └─TableRangeScan_5     | 1.00    | cop[tikv] | table:t       | range:[9,9], keep order:false, stats:pseudo |
+------------------------+---------+-----------+---------------+---------------------------------------------+
2 rows in set (0.001 sec)

MySQL [test]> EXECUTE st1 USING @a;
+---+------+
| a | b    |
+---+------+
| 9 |    9 |
+---+------+
1 row in set (0.001 sec)

MySQL [test]> explain for connection 3;
+------------------------+---------+-----------+---------------+---------------------------------------------+
| id                     | estRows | task      | access object | operator info                               |
+------------------------+---------+-----------+---------------+---------------------------------------------+
| TableReader_6          | 1.00    | root      |               | data:TableRangeScan_5                       |
| └─TableRangeScan_5     | 1.00    | cop[tikv] | table:t       | range:[9,9], keep order:false, stats:pseudo |
+------------------------+---------+-----------+---------------+---------------------------------------------+
2 rows in set (0.000 sec)

it seems EXPLAIN can not show the partiton name after prepare/execute.

[imtbkcat]

I think it better to remove:
https://github.com/pingcap/tidb/blob/master/planner/core/common_plans.go#L444
https://github.com/pingcap/tidb/blob/master/planner/core/common_plans.go#L463
https://github.com/pingcap/tidb/blob/master/planner/core/common_plans.go#L478
https://github.com/pingcap/tidb/blob/master/planner/core/common_plans.go#L523
https://github.com/pingcap/tidb/blob/master/planner/core/common_plans.go#L535

[winoros]

Don't we need to add some new tests?

[ti-srebot]

@zz-jason, @imtbkcat, @winoros, @lysu, @SunRunAway, @eurekaka, PTAL.

[sre-bot]

No release note, Please follow https://github.com/pingcap/community/blob/master/contributors/release-note-checker.md

[tiancaiamao]

PTAL @winoros

[winoros]

lgtm

[lysu]

/rebuild

[lysu]

/merge

[ti-srebot]

/run-all-tests

[ti-srebot]

@tiancaiamao merge failed.

[lysu]

/merge

[ti-srebot]

/run-all-tests

[ti-srebot]

@tiancaiamao merge failed.

[tiancaiamao]

/run-all-tests

[lysu]

/merge

[ti-srebot]

Your auto merge job has been accepted, waiting for:

• 19846

[ti-srebot]

/run-all-tests

[ti-srebot]

@tiancaiamao merge failed.

[tiancaiamao]

/merge

[ti-srebot]

/run-all-tests