expressions: operator supports []byte type

…ap#39)

* support statement-size

* support statement-size

* add unit test

Co-authored-by: 3pointer <luancheng@pingcap.com>

* init

* audit: init first version of audit log

* audit: support log global rotate

* audit: update log keys

* audit: more common notify implement

* audit: add record id

* audit: rename some names

* audit: default use normal log path

* audit: add server ip info

* audit: do some refine

* audit: Add some log keys

* audit: update some item format

* audit: add stmt demo

* audit: support redact

* audit: fix bug

* audit: update filter

* audit: update filter

* audit: check user

* audit: update

* update

* audit: update

* audit: fix bug

* aduit: update

* audit: update

* update

* update

* audit: add filter unit test

* fmt

* Add tests for `tidb_audit_enabled` and `tidb_audit_log`

* Add tests for `tidb_audit_log_max_size` and `tidb_audit_log_max_lifetime`

* Add tests for `tidb_audit_log_reserved_*`

* TODO: TestAuditLogRedact

* Fininsh `TestAuditLogRedact`

* Update (pingcap#1)

* fix typo (pingcap#2)

* Add `TRANSACTION`

* rename sysvar

* audit_log_create_filter, audit_log_remove_filter

* finish function call and table test

* test privilege

* finish test for sysvar

* TODO: TestConnectionEvenClass

* update

* audit: fix lint for audit log (pingcap#1)

* audit: fix UT failure caused by the change of redact log (pingcap#3)

* audit: use `t.TempDir()` to make test stable (pingcap#4)

* audit: fix test failed for 7.1

* Add `OWNERS` file (pingcap#35)

Co-authored-by: Chao Wang <cclcwangchao@hotmail.com>

* audit: fix panic when logging sometime (pingcap#26) (pingcap#31)

* test: fix unstable test TestAuditLogReservedDays (pingcap#8)

* Format sysvar_test.go

* audit: use `StatementContext` to generate redacted SQL (pingcap#9)

* audit: fix panic when logging sometime (pingcap#26)

* update

* add owner

* Update OWNERS

---------

Co-authored-by: CbcWestwolf <1004626265@qq.com>
Co-authored-by: wuhuizuo <wuhuizuo@126.com>

* audit: fix panic sometimes when `create user` without password (pingcap#37) (pingcap#39)

* This is an automated cherry-pick of pingcap#37

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

* fix conflict

---------

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
Co-authored-by: 王超 <cclcwangchao@hotmail.com>

* extension/audit: introduce serverless audit log

Signed-off-by: Wen Jiazhi <jiazhi.wen@pingcap.com>

* update bazel config

Signed-off-by: Wen Jiazhi <jiazhi.wen@pingcap.com>

* support enable audit log when activate

Signed-off-by: Wen Jiazhi <jiazhi.wen@pingcap.com>

* add gwconnid to audit log

Signed-off-by: Wen Jiazhi <jiazhi.wen@pingcap.com>

* comment unstable test

* update bazel

* add log about activate request

* diff audit log enabled

* audit: fix memory leak for executeSQL (pingcap#44) (pingcap#45)

* This is an automated cherry-pick of pingcap#44

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>

* Update util.go

---------

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
Co-authored-by: 王超 <cclcwangchao@hotmail.com>

* Update extension/serverless/OWNERS

---------

Signed-off-by: ti-chi-bot <ti-community-prow-bot@tidb.io>
Signed-off-by: Wen Jiazhi <jiazhi.wen@pingcap.com>
Co-authored-by: Chao Wang <cclcwangchao@hotmail.com>
Co-authored-by: cbcwestwolf <1004626265@qq.com>
Co-authored-by: Ti Chi Robot <ti-community-prow-bot@tidb.io>
Co-authored-by: wuhuizuo <wuhuizuo@126.com>
Co-authored-by: zzm <zhouzemin@pingcap.com>
Co-authored-by: Yuqing Bai <baiyuq@gmail.com>

… (pingcap#39)

close pingcap#50359

Co-authored-by: Ti Chi Robot <ti-community-prow-bot@tidb.io>

This reverts commit 7748805.

This reverts commit 7748805.

This reverts commit 7748805.

…cap#39)

<!--

Thank you for contributing to TiDB!

PR Title Format:
1. pkg [, pkg2, pkg3]: what's changed
2. *: what's changed

-->

### What problem does this PR solve?
<!--

Please create an issue first to describe the problem.

There MUST be one line starting with "Issue Number:  " and
linking the relevant issues via the "close" or "ref".

For more info, check https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/contribute-code.html#referring-to-an-issue.

-->

行为参考：https://docs.oracle.com/en/database/oracle/oracle-database/21/sqlrf/SYS_CONTEXT.html
1. CURRENT_SCHEMA
未选择 Schema：

```
mysql> SELECT SYS_CONTEXT('USERENV', 'CURRENT_SCHEMA') as CURRENT_SCHEMA FROM dual;
+----------------+
| CURRENT_SCHEMA |
+----------------+
|                |
+----------------+
1 row in set (0.00 sec)
```

选择 test schema：

```
mysql> use test
Database changed
mysql> SELECT SYS_CONTEXT('USERENV', 'CURRENT_SCHEMA') as CURRENT_SCHEMA FROM dual;
+----------------+
| CURRENT_SCHEMA |
+----------------+
| test           |
+----------------+
1 row in set (0.00 sec)
```

1. CURRENT_USER

```
mysql> SELECT SYS_CONTEXT('USERENV', 'CURRENT_USER') as `CURRENT_USER` FROM dual;
+--------------+
| CURRENT_USER |
+--------------+
| root         |
+--------------+
1 row in set (0.00 sec)

mysql> SELECT SYS_CONTEXT('USERENV', 'CURRENT_USER') as CURRENT_USERID FROM dual;
+----------------+
| CURRENT_USERID |
+----------------+
| root           |
+----------------+
1 row in set (0.00 sec)
```

1. SESSIONID

```
mysql> SELECT SYS_CONTEXT('USERENV', 'SESSIONID') as session_id FROM dual;
+------------+
| session_id |
+------------+
| 2097156    |
+------------+
1 row in set (0.00 sec)
```

1. 指定长度参数截断结果

```
mysql> SELECT SYS_CONTEXT('USERENV', 'CURRENT_USER', 3) as CURRENT_USERID FROM dual;
+----------------+
| CURRENT_USERID |
+----------------+
| roo            |
+----------------+
1 row in set (0.00 sec)

```

1. 各种错误

```
# 指定的参数不存在
mysql> SELECT SYS_CONTEXT('USERENV', 'NE') as CURRENT_USERID FROM dual;
ERROR 1105 (HY000): invalid USERENV parameter

# 指定的命名空间不存在
mysql> SELECT SYS_CONTEXT('NE', 'NE') as session_id FROM dual;
ERROR 1105 (HY000): invalid namespace

# 参数数量传少或传多
mysql> SELECT SYS_CONTEXT('NE') as session_id FROM dual;
ERROR 1582 (42000): Incorrect parameter count in the call to native function 'sys_context'

mysql> SELECT SYS_CONTEXT('NE', 'NE', 4, 4) as session_id FROM dual;
ERROR 1582 (42000): Incorrect parameter count in the call to native function 'sys_context'
```

### What changed and how does it work?

### Check List

Tests <!-- At least one of them must be included. -->

- [ ] Unit test
- [ ] Integration test
- [x] Manual test (add detailed scripts or steps below)
- [ ] No need to test
  > - [ ] I checked and no code files have been changed.
  > <!-- Or your custom  "No need to test" reasons -->

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

<!-- compatibility change, improvement, bugfix, and new feature need a release note -->

Please refer to [Release Notes Language Style Guide](https://pingcap.github.io/tidb-dev-guide/contribute-to-tidb/release-notes-style-guide.html) to write a quality release note.

```release-note
None
```

Reviewed-on: https://git.pingcap.net/pingkai/tidb/pulls/39
Reviewed-by: crazycs520 <chenshuang@pingcap.cn>