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Merge pull request #17116 from taosdata/docs/3.0_query_doc 

docs: improve the system table chapter
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wade zhang 2022-09-28 15:36:49 +08:00 committed by GitHub
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16
docs/en/12-taos-sql/22-meta.md
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@ -11,7 +11,15 @@ TDengine includes a built-in database named `INFORMATION_SCHEMA` to provide acce
4. Future versions of TDengine can add new columns to INFORMATION_SCHEMA tables without affecting existing business systems.
5. It is easier for users coming from other database management systems. For example, Oracle users can query data dictionary tables.
Note: SHOW statements are still supported for the convenience of existing users.
:::info
- SHOW statements are still supported for the convenience of existing users.
- Some columns in the system table may be keywords, and you need to use the escape character '\`' when querying, for example, to query the VGROUPS in the database `test`:
```sql
select `vgroups` from ins_databases where name = 'test';
```
:::
This document introduces the tables of INFORMATION_SCHEMA and their structure.
@ -102,7 +110,11 @@ Provides information about user-created databases. Similar to SHOW DATABASES.
| 24 | wal_retention_period | INT | WAL retention period |
| 25 | wal_retention_size | INT | Maximum WAL size |
| 26 | wal_roll_period | INT | WAL rotation period |
| 27 | wal_segment_size | WAL file size |
| 27 | wal_segment_size | BIGINT | WAL file size |
| 28 | stt_trigger | SMALLINT | The threshold for number of files to trigger file merging |
| 29 | table_prefix | SMALLINT | The prefix length in the table name that is ignored when distributing table to vnode based on table name |
| 30 | table_suffix | SMALLINT | The suffix length in the table name that is ignored when distributing table to vnode based on table name |
| 31 | tsdb_pagesize | INT | The page size for internal storage engine, its unit is KB |
## INS_FUNCTIONS

16
docs/zh/12-taos-sql/22-meta.md
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@ -12,7 +12,15 @@ TDengine 内置了一个名为 `INFORMATION_SCHEMA` 的数据库，提供对数
4. TDengine 在后续演进中可以灵活的添加已有 INFORMATION_SCHEMA 中表的列，而不用担心对既有业务系统造成影响
5. 与其他数据库系统更具互操作性。例如，Oracle 数据库用户熟悉查询 Oracle 数据字典中的表
Note: 由于 SHOW 语句已经被开发者熟悉和广泛使用，所以它们仍然被保留。
:::info
- 由于 SHOW 语句已经被开发者熟悉和广泛使用，所以它们仍然被保留。
- 系统表中的一些列可能是关键字，在查询时需要使用转义符'\`'，例如查询数据库 test 有几个 VGROUP：
```sql
select `vgroups` from ins_databases where name = 'test';
```
:::
本章将详细介绍 `INFORMATION_SCHEMA` 这个内置元数据库中的表和表结构。
@ -103,7 +111,11 @@ Note: 由于 SHOW 语句已经被开发者熟悉和广泛使用，所以它们
| 24 | wal_retention_period | INT | WAL 的保存时长 |
| 25 | wal_retention_size | INT | WAL 的保存上限 |
| 26 | wal_roll_period | INT | wal 文件切换时长 |
| 27 | wal_segment_size | wal 单个文件大小 |
| 27 | wal_segment_size | BIGINT | wal 单个文件大小 |
| 28 | stt_trigger | SMALLINT | 触发文件合并的落盘文件的个数 |
| 29 | table_prefix | SMALLINT | 内部存储引擎根据表名分配存储该表数据的 VNODE 时要忽略的前缀的长度 |
| 30 | table_suffix | SMALLINT | 内部存储引擎根据表名分配存储该表数据的 VNODE 时要忽略的后缀的长度 |
| 31 | tsdb_pagesize | INT | 时序数据存储引擎中的页大小 |
## INS_FUNCTIONS