planner: support Hypo indexes

[qw4990]

What problem does this PR solve?

Issue Number: close #43817

Problem Summary: support Hypo indexes

What is changed and how it works?

1. Support to use create index {name} type hypo on {table} (c1, c2) to create hypo-indexes;
2. Support to use drop index to remove hypo-indexes;
3. Show create table can show all hypo-indexes;

Usage:

mysql> create table t (a int);
Query OK, 0 rows affected (0.03 sec)

mysql> explain select a from t where a = 1; -- no hypo-index
+-------------------------+----------+-----------+---------------+--------------------------------+
| id                      | estRows  | task      | access object | operator info                  |
+-------------------------+----------+-----------+---------------+--------------------------------+
| TableReader_7           | 10.00    | root      |               | data:Selection_6               |
| └─Selection_6           | 10.00    | cop[tikv] |               | eq(test.t.a, 1)                |
|   └─TableFullScan_5     | 10000.00 | cop[tikv] | table:t       | keep order:false, stats:pseudo |
+-------------------------+----------+-----------+---------------+--------------------------------+
3 rows in set (0.00 sec)

mysql> create index hypo_a type hypo on t (a);
Query OK, 0 rows affected (0.01 sec)

mysql> show create table t;
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table                                                                                                                                     |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------+
| t     | CREATE TABLE `t` (
  `a` int(11) DEFAULT NULL,
  KEY `hypo_a` (`a`) /* HYPO INDEX */
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin |
+-------+--------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.01 sec)

mysql> explain select a from t where a = 1;
+------------------------+---------+-----------+--------------------------+---------------------------------------------+
| id                     | estRows | task      | access object            | operator info                               |
+------------------------+---------+-----------+--------------------------+---------------------------------------------+
| IndexReader_6          | 10.00   | root      |                          | index:IndexRangeScan_5                      |
| └─IndexRangeScan_5     | 10.00   | cop[tikv] | table:t, index:hypo_a(a) | range:[1,1], keep order:false, stats:pseudo |
+------------------------+---------+-----------+--------------------------+---------------------------------------------+
2 rows in set (0.00 sec)

mysql> drop index hypo_a on t;
Query OK, 0 rows affected (0.01 sec);

Check List

Tests

• Unit test
• Integration test
• Manual test (add detailed scripts or steps below)
• No code

Side effects

• Performance regression: Consumes more CPU
• Performance regression: Consumes more Memory
• Breaking backward compatibility

Documentation

• Affects user behaviors
• Contains syntax changes
• Contains variable changes
• Contains experimental features
• Changes MySQL compatibility

Release note

Please refer to Release Notes Language Style Guide to write a quality release note.

None

[ti-chi-bot]

[REVIEW NOTIFICATION]

This pull request has been approved by:

• chrysan
• hawkingrei

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[qw4990]

/merge

[ti-chi-bot]

This pull request has been accepted and is ready to merge.

Commit hash: a7ed181

[bb7133]

LGTM

[bb7133]

/merge