Merge branch '3.0' of https://github.com/taosdata/TDengine into feat/stream_compression

docs/en/12-taos-sql/06-select.md

@@ -181,6 +181,14 @@ In TDengine, the first column of all tables must be a timestamp. This column is
 select _rowts, max(current) from meters;
 ```
 
+**\_IROWTS**
+
+The \_IROWTS pseudocolumn can only be used with INTERP function. This pseudocolumn can be used to retrieve the corresponding timestamp column associated with the interpolation results.
+
+```sql
+select _irowts, interp(current) from meters range('2020-01-01 10:00:00', '2020-01-01 10:30:00') every(1s) fill(linear);
+```
+
 ## Query Objects
 
 `FROM` can be followed by a number of tables or super tables, or can be followed by a sub-query.

docs/en/12-taos-sql/20-keywords.md

@@ -343,6 +343,7 @@ The following list shows all reserved keywords:
 ### \_
 
 - \_C0
+- \_IROWTS
 - \_QDURATION
 - \_QEND
 - \_QSTART

docs/en/12-taos-sql/29-changes.md

@@ -11,12 +11,13 @@ description: "This document explains how TDengine SQL has changed in version 3.0
 | 1 | VARCHAR | Added | Alias of BINARY.
 | 2 | TIMESTAMP literal | Added | TIMESTAMP 'timestamp format' syntax now supported.
 | 3 | _ROWTS pseudocolumn | Added | Indicates the primary key. Alias of _C0.
-| 4 | INFORMATION_SCHEMA | Added |	Database for system metadata containing all schema definitions
-| 5 | PERFORMANCE_SCHEMA | Added | Database for system performance information.
-| 6 | Connection queries | Deprecated | Connection queries are no longer supported. The syntax and interfaces are deprecated.
-| 7 | Mixed operations | Enhanced | Mixing scalar and vector operations in queries has been enhanced and is supported in all SELECT clauses.
-| 8 | Tag operations | Added | Tag columns can be used in queries and clauses like data columns.
-| 9 | Timeline clauses and time functions in supertables | Enhanced | When PARTITION BY is not used, data in supertables is merged into a single timeline.
+| 4 | _IROWTS pseudocolumn | Added | Used to retrieve timestamps with INTERP function.
+| 5 | INFORMATION_SCHEMA | Added |	Database for system metadata containing all schema definitions
+| 6 | PERFORMANCE_SCHEMA | Added | Database for system performance information.
+| 7 | Connection queries | Deprecated | Connection queries are no longer supported. The syntax and interfaces are deprecated.
+| 8 | Mixed operations | Enhanced | Mixing scalar and vector operations in queries has been enhanced and is supported in all SELECT clauses.
+| 9 | Tag operations | Added | Tag columns can be used in queries and clauses like data columns.
+| 10 | Timeline clauses and time functions in supertables | Enhanced | When PARTITION BY is not used, data in supertables is merged into a single timeline.
 
 ## SQL Syntax
 

docs/zh/12-taos-sql/06-select.md

@@ -182,6 +182,14 @@ TDengine 中，所有表的第一列都必须是时间戳类型，且为其主
 select _rowts, max(current) from meters;
 ```
 
+**\_IROWTS**
+
+\_irowts 伪列只能与 interp 函数一起使用，用于返回 interp 函数插值结果对应的时间戳列。
+
+```sql
+select _irowts, interp(current) from meters range('2020-01-01 10:00:00', '2020-01-01 10:30:00') every(1s) fill(linear);
+```
+
 ## 查询对象
 
 FROM 关键字后面可以是若干个表（超级表）列表，也可以是子查询的结果。

docs/zh/12-taos-sql/20-keywords.md

@@ -344,6 +344,7 @@ description: TDengine 保留关键字的详细列表
 ### \_
 
 - \_C0
+- \_IROWTS
 - \_QDURATION
 - \_QEND
 - \_QSTART

docs/zh/12-taos-sql/29-changes.md

@@ -11,12 +11,13 @@ description: "TDengine 3.0 版本的语法变更说明"
 | 1 | VARCHAR | 新增 | BINARY类型的别名。
 | 2 | TIMESTAMP字面量 | 新增 | 新增支持 TIMESTAMP 'timestamp format' 语法。
 | 3 | _ROWTS伪列 | 新增 | 表示时间戳主键。是_C0伪列的别名。
-| 4 | INFORMATION_SCHEMA | 新增 |	包含各种SCHEMA定义的系统数据库。
-| 5 | PERFORMANCE_SCHEMA | 新增 | 包含运行信息的系统数据库。
-| 6 | 连续查询 | 废除 | 不再支持连续查询。相关的各种语法和接口废除。
-| 7 | 混合运算 | 增强 | 查询中的混合运算（标量运算和矢量运算混合）全面增强，SELECT的各个子句均全面支持符合语法语义的混合运算。
-| 8 | 标签运算 | 新增 |在查询中，标签列可以像普通列一样参与各种运算，用于各种子句。
-| 9 | 时间线子句和时间函数用于超级表查询 | 增强 |没有PARTITION BY时，超级表的数据会被合并成一条时间线。
+| 4 | _IROWTS伪列 | 新增 | 用于返回 interp 函数插值结果对应的时间戳列。
+| 5 | INFORMATION_SCHEMA | 新增 |	包含各种SCHEMA定义的系统数据库。
+| 6 | PERFORMANCE_SCHEMA | 新增 | 包含运行信息的系统数据库。
+| 7 | 连续查询 | 废除 | 不再支持连续查询。相关的各种语法和接口废除。
+| 8 | 混合运算 | 增强 | 查询中的混合运算（标量运算和矢量运算混合）全面增强，SELECT的各个子句均全面支持符合语法语义的混合运算。
+| 9 | 标签运算 | 新增 |在查询中，标签列可以像普通列一样参与各种运算，用于各种子句。
+| 10 | 时间线子句和时间函数用于超级表查询 | 增强 |没有PARTITION BY时，超级表的数据会被合并成一条时间线。
 
 ## SQL 语句变更