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docs: add para_tables_sort() hint

This commit is contained in:
slzhou 2024-02-21 13:39:15 +08:00
parent 6b331594d9
commit 35aed76539
2 changed files with 7 additions and 4 deletions
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6
docs/en/12-taos-sql/06-select.md
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@ -24,7 +24,7 @@ SELECT [hints] [DISTINCT] [TAGS] select_list
hints: /*+ [hint([hint_param_list])] [hint([hint_param_list])] */
hint:
BATCH_SCAN | NO_BATCH_SCAN | SORT_FOR_GROUP
BATCH_SCAN | NO_BATCH_SCAN | SORT_FOR_GROUP | PARA_TABLES_SORT
select_list:
select_expr [, select_expr] ...
@ -87,12 +87,13 @@ Hints are a means of user control over query optimization for individual stateme
The list of currently supported Hints is as follows:
| **Hint** | **Params** | **Comment** | **Scopt** |
| **Hint** | **Params** | **Comment** | **Scope** |
| :-----------: | -------------- | -------------------------- | -----------------------------------|
| BATCH_SCAN | None | Batch table scan | JOIN statment for stable |
| NO_BATCH_SCAN | None | Sequential table scan | JOIN statment for stable |
| SORT_FOR_GROUP| None | Use sort for partition, conflict with PARTITION_FIRST | With normal column in partition by list |
| PARTITION_FIRST| None | Use Partition before aggregate, conflict with SORT_FOR_GROUP | With normal column in partition by list |
| PARA_TABLES_SORT| None | When sorting the supertable rows by timestamp, No temporary disk space is used | Sorting the supertable rows by timestamp |
For example:
@ -100,6 +101,7 @@ For example:
SELECT /*+ BATCH_SCAN() */ a.ts FROM stable1 a, stable2 b where a.tag0 = b.tag0 and a.ts = b.ts;
SELECT /*+ SORT_FOR_GROUP() */ count(*), c1 FROM stable1 PARTITION BY c1;
SELECT /*+ PARTITION_FIRST() */ count(*), c1 FROM stable1 PARTITION BY c1;
SELECT /*+ PARA_TABLES_SORT() */ * from stable1 order by ts;
```
## Lists

5
docs/zh/12-taos-sql/06-select.md
View File

@ -24,7 +24,7 @@ SELECT [hints] [DISTINCT] [TAGS] select_list
hints: /*+ [hint([hint_param_list])] [hint([hint_param_list])] */
hint:
BATCH_SCAN | NO_BATCH_SCAN | SORT_FOR_GROUP
BATCH_SCAN | NO_BATCH_SCAN | SORT_FOR_GROUP | PARA_TABLES_SORT
select_list:
select_expr [, select_expr] ...
@ -93,13 +93,14 @@ Hints 是用户控制单个语句查询优化的一种手段，当 Hint 不适
| NO_BATCH_SCAN | 无 | 采用顺序读表的方式 | 超级表 JOIN 语句 |
| SORT_FOR_GROUP| 无 | 采用sort方式进行分组, 与PARTITION_FIRST冲突 | partition by 列表有普通列时 |
| PARTITION_FIRST| 无 | 在聚合之前使用PARTITION计算分组, 与SORT_FOR_GROUP冲突 | partition by 列表有普通列时 |
| PARA_TABLES_SORT| 无 | 超级表的数据按时间戳排序时, 不使用临时磁盘空间, 只使用内存 | 超级表的数据按时间戳排序时 |
举例：
```sql
SELECT /*+ BATCH_SCAN() */ a.ts FROM stable1 a, stable2 b where a.tag0 = b.tag0 and a.ts = b.ts;
SELECT /*+ SORT_FOR_GROUP() */ count(*), c1 FROM stable1 PARTITION BY c1;
SELECT /*+ PARTITION_FIRST() */ count(*), c1 FROM stable1 PARTITION BY c1;
SELECT /*+ PARA_TABLES_SORT() */ * from stable1 order by ts;
```
## 列表