Node(kind: nkInt, intVal: 4), rightOp: Node(kind: nkInt, intVal: 2)) # 有效:不更改活动对象分⽀: x.kind = nkSub 从版本 0.20 开始 system.reset 不能再⽤于⽀持对象分⽀的更改，因为这始终不是完全内存安全的。 作为⼀项特殊规则，鉴别字段类型也可以使⽤ case 语句来限制。如果 case 语句分⽀中的鉴别字段变量的可能值是所选对象分⽀ 编译指示对于开发者来说也是⼀种提醒: 这个基⽅法 m 是推断⽅法 m 所能产⽣的所有效果的⼀个基础。 注意: ⽬前还不⽀持⽅法的编译期执⾏。 注意: 从 Nim 0.20 开始，泛型⽅法已被弃⽤。 多重⽅法 (Multi-methods) Note 从 Nim 0.20 开始，要启⽤多重⽅法，开发者必须在编译时显式添加 --multimethods:on 参数。 在多重⽅法中，所有对象类型的参数都会⽤于⽅法派发:

线程公平性 execution time (avg/ stddev) 159.0818/0.01 341.2010/0.01 3397.3404/0.05 84.0706/0.01 456.9469/0.20 测试⼆ 测试⼆ 版本: v3.0.5 线程: 512 表: 32 * 6000万条数据 数据量约1.3T 事务: 1000万 测试时间: 600(s) sysbench: v1.0.13 跨可⽤区类型

20::36 36::03 03 || ++---------------------+ ---------------------+ 11 row row inin set set ((0.20 0.20 sec sec)) second second((string string date date)) Baidu 百度智能云文档 SQL手册 169 Keywords Keywords

-------------------------+-------------------------------------------------+ �→ | IndexMerge_8 | 0.20 | root | �→ | type: union �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t5, index:idx(a signed array)) | range:[2 2,2 2], keep order:false, stats:pseudo | | └─ TableRowIDScan_7(Probe) | 0.20 | cop[tikv] | table:t5 �→ | keep order:false, stats:pseudo �→ | +-- �→ ---------------------- ---------------------------------------------------------------------------+ �→ | IndexMerge_9 | 0.20 | root | �→ | type: union �→ �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t6, index:idx(a

-------------------------+-------------------------------------------------+ �→ | IndexMerge_8 | 0.20 | root | �→ | type: union �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t5, index:idx(a signed array)) | range:[2 2,2 2], keep order:false, stats:pseudo | | └─ TableRowIDScan_7(Probe) | 0.20 | cop[tikv] | table:t5 �→ | keep order:false, stats:pseudo �→ | +-- �→ ---------------------- ---------------------------------------------------------------------------+ �→ | IndexMerge_9 | 0.20 | root | �→ | type: union �→ �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t6, index:idx(a

-------------------------+-------------------------------------------------+ �→ | IndexMerge_8 | 0.20 | root | �→ | type: union �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t5, index:idx(a signed array)) | range:[2 2,2 2], keep order:false, stats:pseudo | | └─ TableRowIDScan_7(Probe) | 0.20 | cop[tikv] | table:t5 �→ | keep order:false, stats:pseudo �→ | +-- �→ ---------------------- ---------------------------------------------------------------------------+ �→ | IndexMerge_9 | 0.20 | root | �→ | type: union �→ �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t6, index:idx(a

-------------------------+-------------------------------------------------+ �→ | IndexMerge_8 | 0.20 | root | �→ | type: union �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t5, index:idx(a signed array)) | range:[2 2,2 2], keep order:false, stats:pseudo | | └─ TableRowIDScan_7(Probe) | 0.20 | cop[tikv] | table:t5 �→ | keep order:false, stats:pseudo �→ | +-- �→ ---------------------- ---------------------------------------------------------------------------+ �→ | IndexMerge_9 | 0.20 | root | �→ | type: union �→ �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t6, index:idx(a

-------------------------+-------------------------------------------------+ �→ | IndexMerge_8 | 0.20 | root | �→ | type: union �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t5, index:idx(a signed array)) | range:[2 2,2 2], keep order:false, stats:pseudo | | └─ TableRowIDScan_7(Probe) | 0.20 | cop[tikv] | table:t5 �→ | keep order:false, stats:pseudo �→ | +-- �→ ---------------------- ---------------------------------------------------------------------------+ �→ | IndexMerge_9 | 0.20 | root | �→ | type: union �→ �→ | | ├─ IndexRangeScan_5(Build) | 0.10 | cop[tikv] | table:t6, index:idx(a

-+---------------- -------------------------------------------------------------+ 1 row in set (0.20 sec) DB Discovery Type mysql> show db_discovery types; +--------------------------+------+----

-+----------- ------------------------------------------------------------------+ 1 row in set (0.20 sec) DB Discovery Type mysql> SHOW DB_DISCOVERY TYPES; +--------------------------+-----------