ddl: Only warn of subpartitions, still allow first level partitioning

[mjonss]

What problem does this PR solve?

Issue Number: close #41198 , close #41200

Problem Summary:
For LIST partitioning, it did not check if SUBPARTITION was used and just stripped the subpartition part
For RANGE and HASH partitioning it stripped all partitioning and added a warning that such partitioning was not supported.

What is changed and how it works?

Combine the two behaviours:
Strip the subpartitioning from the CREATE TABLE statement and issue a warning.

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.

If CREATE TABLE includes subpartitions, keep the normal partitioning and skip the subpartitioning + add a warning.

[ti-chi-bot]

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• Defined2014
• TonsnakeLin

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[mjonss]

Also fixes #41200

tidb> CREATE TABLE thash15 ( col1 INT NOT NULL, col2 INT NOT NULL, col3 INT NOT NULL, col4 INT NOT NULL, primary KEY (col1,col3) ) PARTITION BY HASH(col1) PARTITIONS 4 SUBPARTITION BY HASH(col3) SUBPARTITIONS 2;
Query OK, 0 rows affected, 1 warning (0.04 sec)

tidb> show warnings;
+---------+------+-----------------------------------------------------------+
| Level   | Code | Message                                                   |
+---------+------+-----------------------------------------------------------+
| Warning | 8200 | Unsupported subpartitioning, only using HASH partitioning |
+---------+------+-----------------------------------------------------------+
1 row in set (0.00 sec)

[mjonss]

/retest

[mjonss]

/retest

[TonsnakeLin]

I think it is reasonable for #41198, but it's not reasonable for #41200 which gives an error like "It is only possible to mix RANGE/LIST partitioning with HASH/KEY partitioning for subpartitioning" in MySQL.

[TonsnakeLin]

In addition, should we modify the document about partition if we fixed the issue.

[mjonss]

I think it is reasonable for #41198, but it's not reasonable for #41200 which gives an error like "It is only possible to mix RANGE/LIST partitioning with HASH/KEY partitioning for subpartitioning" in MySQL.

I have changed the logic so it will give that error if subpartitioning a HASH or KEY partitioned table, just like MySQL.

[TonsnakeLin]

LGTM execep the empty line and spaces I commented

[mjonss]

/retest

[Defined2014]

/merge

[ti-chi-bot]

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

Commit hash: 2dee8ca

[mjonss]

/merge

[ti-chi-bot]

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

Commit hash: baa57b8

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.5: #43887.

[ti-chi-bot]

In response to a cherrypick label: new pull request created to branch release-6.1: #43888.