Merge branch '3.0' of https://github.com/taosdata/TDengine into refact/tsdb_last

docs/examples/go/connect/afconn/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"log"
 
 	"github.com/taosdata/driver-go/v3/af"
 )
@@ -10,7 +11,7 @@ func main() {
 	conn, err := af.Open("localhost", "root", "taosdata", "", 6030)
 	defer conn.Close()
 	if err != nil {
-		fmt.Println("failed to connect, err:", err)
+		log.Fatalln("failed to connect, err:", err)
 	} else {
 		fmt.Println("connected")
 	}

docs/examples/go/connect/cgoexample/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"database/sql"
 	"fmt"
+	"log"
 
 	_ "github.com/taosdata/driver-go/v3/taosSql"
 )
@@ -11,7 +12,7 @@ func main() {
 	var taosDSN = "root:taosdata@tcp(localhost:6030)/"
 	taos, err := sql.Open("taosSql", taosDSN)
 	if err != nil {
-		fmt.Println("failed to connect TDengine, err:", err)
+		log.Fatalln("failed to connect TDengine, err:", err)
 		return
 	}
 	fmt.Println("Connected")

docs/examples/go/connect/restexample/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"database/sql"
 	"fmt"
+	"log"
 
 	_ "github.com/taosdata/driver-go/v3/taosRestful"
 )
@@ -11,7 +12,7 @@ func main() {
 	var taosDSN = "root:taosdata@http(localhost:6041)/"
 	taos, err := sql.Open("taosRestful", taosDSN)
 	if err != nil {
-		fmt.Println("failed to connect TDengine, err:", err)
+		log.Fatalln("failed to connect TDengine, err:", err)
 		return
 	}
 	fmt.Println("Connected")

docs/examples/go/connect/wrapper/main.go

-package main
-
-import (
-	"fmt"
-
-	"github.com/taosdata/driver-go/v3/wrapper"
-)
-
-func main() {
-	conn, err := wrapper.TaosConnect("localhost", "root", "taosdata", "", 6030)
-	defer wrapper.TaosClose(conn)
-	if err != nil {
-		fmt.Println("fail to connect, err:", err)
-	} else {
-		fmt.Println("connected")
-	}
-}

docs/examples/go/insert/json/main.go

 package main
 
 import (
-	"fmt"
+	"log"
 
 	"github.com/taosdata/driver-go/v3/af"
 )
@@ -20,7 +20,7 @@ func prepareDatabase(conn *af.Connector) {
 func main() {
 	conn, err := af.Open("localhost", "root", "taosdata", "", 6030)
 	if err != nil {
-		fmt.Println("fail to connect, err:", err)
+		log.Fatalln("fail to connect, err:", err)
 	}
 	defer conn.Close()
 	prepareDatabase(conn)
@@ -32,6 +32,6 @@ func main() {
 
 	err = conn.OpenTSDBInsertJsonPayload(payload)
 	if err != nil {
-		fmt.Println("insert error:", err)
+		log.Fatalln("insert error:", err)
 	}
 }

docs/examples/go/insert/line/main.go

@@ -2,6 +2,7 @@ package main
 
 import (
 	"fmt"
+	"log"
 
 	"github.com/taosdata/driver-go/v3/af"
 )
@@ -33,6 +34,6 @@ func main() {
 
 	err = conn.InfluxDBInsertLines(lines, "ms")
 	if err != nil {
-		fmt.Println("insert error:", err)
+		log.Fatalln("insert error:", err)
 	}
 }

docs/examples/go/insert/sql/main.go

@@ -3,6 +3,7 @@ package main
 import (
 	"database/sql"
 	"fmt"
+	"log"
 
 	_ "github.com/taosdata/driver-go/v3/taosRestful"
 )
@@ -10,28 +11,26 @@ import (
 func createStable(taos *sql.DB) {
 	_, err := taos.Exec("CREATE DATABASE power")
 	if err != nil {
-		fmt.Println("failed to create database, err:", err)
+		log.Fatalln("failed to create database, err:", err)
 	}
 	_, err = taos.Exec("CREATE STABLE power.meters (ts TIMESTAMP, current FLOAT, voltage INT, phase FLOAT) TAGS (location BINARY(64), groupId INT)")
 	if err != nil {
-		fmt.Println("failed to create stable, err:", err)
+		log.Fatalln("failed to create stable, err:", err)
 	}
 }
 
 func insertData(taos *sql.DB) {
-	sql := `INSERT INTO power.d1001 USING power.meters TAGS(California.SanFrancisco, 2) VALUES ('2018-10-03 14:38:05.000', 10.30000, 219, 0.31000) ('2018-10-03 14:38:15.000', 12.60000, 218, 0.33000) ('2018-10-03 14:38:16.800', 12.30000, 221, 0.31000)
-	power.d1002 USING power.meters TAGS(California.SanFrancisco, 3) VALUES ('2018-10-03 14:38:16.650', 10.30000, 218, 0.25000)
-	power.d1003 USING power.meters TAGS(California.LosAngeles, 2) VALUES ('2018-10-03 14:38:05.500', 11.80000, 221, 0.28000) ('2018-10-03 14:38:16.600', 13.40000, 223, 0.29000)
-	power.d1004 USING power.meters TAGS(California.LosAngeles, 3) VALUES ('2018-10-03 14:38:05.000', 10.80000, 223, 0.29000) ('2018-10-03 14:38:06.500', 11.50000, 221, 0.35000)`
+	sql := `INSERT INTO power.d1001 USING power.meters TAGS('California.SanFrancisco', 2) VALUES ('2018-10-03 14:38:05.000', 10.30000, 219, 0.31000) ('2018-10-03 14:38:15.000', 12.60000, 218, 0.33000) ('2018-10-03 14:38:16.800', 12.30000, 221, 0.31000)
+	power.d1002 USING power.meters TAGS('California.SanFrancisco', 3) VALUES ('2018-10-03 14:38:16.650', 10.30000, 218, 0.25000)
+	power.d1003 USING power.meters TAGS('California.LosAngeles', 2) VALUES ('2018-10-03 14:38:05.500', 11.80000, 221, 0.28000) ('2018-10-03 14:38:16.600', 13.40000, 223, 0.29000)
+	power.d1004 USING power.meters TAGS('California.LosAngeles', 3) VALUES ('2018-10-03 14:38:05.000', 10.80000, 223, 0.29000) ('2018-10-03 14:38:06.500', 11.50000, 221, 0.35000)`
 	result, err := taos.Exec(sql)
 	if err != nil {
-		fmt.Println("failed to insert, err:", err)
-		return
+		log.Fatalln("failed to insert, err:", err)
 	}
 	rowsAffected, err := result.RowsAffected()
 	if err != nil {
-		fmt.Println("failed to get affected rows, err:", err)
-		return
+		log.Fatalln("failed to get affected rows, err:", err)
 	}
 	fmt.Println("RowsAffected", rowsAffected)
 }
@@ -40,8 +39,7 @@ func main() {
 	var taosDSN = "root:taosdata@http(localhost:6041)/"
 	taos, err := sql.Open("taosRestful", taosDSN)
 	if err != nil {
-		fmt.Println("failed to connect TDengine, err:", err)
-		return
+		log.Fatalln("failed to connect TDengine, err:", err)
 	}
 	defer taos.Close()
 	createStable(taos)

docs/examples/go/insert/stmt/main.go

@@ -5,8 +5,8 @@ import (
 	"time"
 
 	"github.com/taosdata/driver-go/v3/af"
-	"github.com/taosdata/driver-go/v3/af/param"
 	"github.com/taosdata/driver-go/v3/common"
+	"github.com/taosdata/driver-go/v3/common/param"
 )
 
 func checkErr(err error, prompt string) {

docs/examples/go/insert/telnet/main.go

 package main
 
 import (
-	"fmt"
+	"log"
 
 	"github.com/taosdata/driver-go/v3/af"
 )
@@ -20,7 +20,7 @@ func prepareDatabase(conn *af.Connector) {
 func main() {
 	conn, err := af.Open("localhost", "root", "taosdata", "", 6030)
 	if err != nil {
-		fmt.Println("fail to connect, err:", err)
+		log.Fatalln("fail to connect, err:", err)
 	}
 	defer conn.Close()
 	prepareDatabase(conn)
@@ -37,6 +37,6 @@ func main() {
 
 	err = conn.OpenTSDBInsertTelnetLines(lines)
 	if err != nil {
-		fmt.Println("insert error:", err)
+		log.Fatalln("insert error:", err)
 	}
 }

docs/examples/go/query/sync/main.go

@@ -2,7 +2,7 @@ package main
 
 import (
 	"database/sql"
-	"fmt"
+	"log"
 	"time"
 
 	_ "github.com/taosdata/driver-go/v3/taosRestful"
@@ -12,14 +12,12 @@ func main() {
 	var taosDSN = "root:taosdata@http(localhost:6041)/power"
 	taos, err := sql.Open("taosRestful", taosDSN)
 	if err != nil {
-		fmt.Println("failed to connect TDengine, err:", err)
-		return
+		log.Fatalln("failed to connect TDengine, err:", err)
 	}
 	defer taos.Close()
 	rows, err := taos.Query("SELECT ts, current FROM meters LIMIT 2")
 	if err != nil {
-		fmt.Println("failed to select from table, err:", err)
-		return
+		log.Fatalln("failed to select from table, err:", err)
 	}
 
 	defer rows.Close()
@@ -30,9 +28,9 @@ func main() {
 		}
 		err := rows.Scan(&r.ts, &r.current)
 		if err != nil {
-			fmt.Println("scan error:\n", err)
+			log.Fatalln("scan error:\n", err)
 			return
 		}
-		fmt.Println(r.ts, r.current)
+		log.Fatalln(r.ts, r.current)
 	}
 }

docs/zh/07-develop/03-insert-data/_go_stmt.mdx

@@ -3,6 +3,6 @@
 ```
 
 :::tip
-driver-go 的模块 `github.com/taosdata/driver-go/v2/wrapper` 是 C 接口的底层封装。使用这个模块也可以实现参数绑定写入。
+driver-go 的模块 `github.com/taosdata/driver-go/v3/wrapper` 是 C 接口的底层封装。使用这个模块也可以实现参数绑定写入。
 
 :::

docs/zh/07-develop/07-tmq.md

 ---
-sidebar_label: 消息队列
-description: "数据订阅与推送服务。连续写入到 TDengine 中的时序数据能够被自动推送到订阅客户端。"
-title: 消息队列
+sidebar_label: 数据订阅
+description: "数据订阅与推送服务。写入到 TDengine 中的时序数据能够被自动推送到订阅客户端。"
+title: 数据订阅
 ---
 
-基于数据天然的时间序列特性，TDengine 的数据写入（insert）与消息系统的数据发布（pub）逻辑上一致，均可视为系统中插入一条带时间戳的新记录。同时，TDengine 在内部严格按照数据时间序列单调递增的方式保存数据。本质上来说，TDengine 中每一张表均可视为一个标准的消息队列。
+为了帮助应用实时获取写入 TDengine 的数据，或者以事件到达顺序处理数据，TDengine提供了类似消息队列产品的数据订阅、消费接口。这样在很多场景下，采用 TDengine 的时序数据处理系统不再需要集成消息队列产品，比如 kafka, 从而简化系统设计的复杂度，降低运营维护成本。
 
-TDengine 内嵌支持消息订阅与推送服务（下文都简称TMQ）。使用系统提供的 API，用户可使用普通查询语句订阅数据库中的一张或多张表，或整个库。客户端启动订阅后，定时或按需轮询服务器是否有新的记录到达，有新的记录到达就会将结果反馈到客户。
+与 kafka 一样，你需要定义 topic, 但 TDengine 的 topic 可以是一张超级表，或一张子表。不仅如此，你可以通过标签、表名、列、表达式等多种方法过滤所需数据，并且支持对数据进行函数变换、预处理（包括标量udf计算）。与其他消息队列软件相比，这是 TDengine 数据订阅功能的最大的优势，它提供了更大的灵活性，数据的颗粒度可以由应用随时调整，而且数据的过滤交给 TDengine，而不是应用完成，有效的减少传输的数据量。
 
-TMQ提供了提交机制来保证消息队列的可靠性和正确性。在调用方法上，支持自动提交和手动提交。
+消费者订阅 topic 后，可以实时获得最新的数据。多个消费者可以组成一个消费者组 (consumer group), 一个消费者组里的多个消费者共享消费进度，便于多线程分布式的消费数据，提高数据通吐率。但不同消费者组即使消费同一个topic, 并不共享消费进度。一个消费者组可以订阅多个 topic。如果订阅的是超级表，数据可能会分布在多个不同的vnode上，也就是多个shard上，这样一个消费组里有多个消费者可以提高消费效率。TDengine 的消息队列提供了消息的ACK机制，在宕机、重启等复杂环境下确保at least once消费。
+
+为了实现上述功能，TDengine 采用了灵活的 WAL (Write-Ahead-Log) 文件切换与保留机制：可以按照时间或文件大小来保留WAL文件（详见create database语句）。在消费时，TDengine 从 WAL 中获取数据，并经过过滤、变换等操作，将数据推送给消费者。
+
+本文档不对消息队列本身的基础知识做介绍，如果需要了解，请自行搜索。
+
+## 主要数据结构和API
 
 TMQ 的 API 中，与订阅相关的主要数据结构和API如下：
 
@@ -47,7 +53,9 @@ DLL_EXPORT void           tmq_conf_set_auto_commit_cb(tmq_conf_t *conf, tmq_comm
 
 这些 API 的文档请见 [C/C++ Connector](/reference/connector/cpp)，下面介绍一下它们的具体用法（超级表和子表结构请参考“数据建模”一节），完整的示例代码可以在 [tmq.c](https://github.com/taosdata/TDengine/blob/3.0/examples/c/tmq.c) 看到。
 
-一、首先完成建库、建一张超级表和多张子表，并每个子表插入若干条数据记录：
+## 写入数据
+
+首先完成建库、建一张超级表和多张子表操作，然后就可以写入数据了，比如：
 
 ```sql
 drop database if exists tmqdb;
@@ -63,14 +71,15 @@ insert into tmqdb.ctb2 values(now, 2, 2, 'a1')(now+1s, 22, 22, 'a22');
 insert into tmqdb.ctb3 values(now, 3, 3, 'a1')(now+1s, 33, 33, 'a33');
 ```
 
-二、创建topic：
+## 创建topic：
 
 ```sql
 create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
 ```
 
-注：TMQ支持多种订阅类型：
-1、列订阅
+TMQ支持多种订阅类型：
+
+### 列订阅
 
 语法：CREATE TOPIC topic_name as subquery
 通过select语句订阅（包括select *，或select ts, c1等指定列描述订阅，可以带条件过滤、标量函数计算，但不支持聚合函数、不支持时间窗口聚合）
@@ -79,25 +88,18 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
 - 被订阅或用于计算的column和tag不可被删除、修改
 - 若发生schema变更，新增的column不出现在结果中
 
-2、超级表订阅
+### 超级表订阅
 语法：CREATE TOPIC topic_name AS STABLE stbName
 
-- 订阅某超级表的全部数据，schema变更不受限，schema变更后写入的数据将以最新schema返回
-- 在tmq的返回消息中schema是块级别的，每块的schema可能不一样
-- 列变更后写入的数据若未落盘，将以写入时的schema返回
-- 列变更后写入的数据若已落盘，将以落盘时的schema返回
-
-3、db订阅
-语法：CREATE TOPIC topic_name AS DATABASE db_name
-
-- 订阅某一db的全部数据，schema变更不受限
-- 在tmq的返回消息中schema是块级别的，每块的schema可能不一样
-- 列变更后写入的数据若未落盘，将以写入时的schema返回
-- 列变更后写入的数据若已落盘，将以落盘时的schema返回
+与select * from stbName订阅的区别是：
+- 不会限制用户的schema变更
+- 返回的是非结构化的数据：返回数据的schema会随之超级表的schema变化而变化
+- 用户对于要处理的每一个数据块都可能有不同的schema，因此，必须重新获取schema
+- 返回数据不带有tag
 
-三、创建consumer
+## 创建 consumer 以及consumer group
 
-目前支持的config：
+对于consumer, 目前支持的config包括：
 
 | 参数名称                     | 参数值                         | 备注                                                   |
 | ---------------------------- | ------------------------------ | ------------------------------------------------------ |
@@ -121,7 +123,7 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
   tmq_conf_set(conf, "group.id", "cgrpName");
   tmq_conf_set(conf, "td.connect.user", "root");
   tmq_conf_set(conf, "td.connect.pass", "taosdata");
-  tmq_conf_set(conf, "auto.offset.reset", "earliest");  
+  tmq_conf_set(conf, "auto.offset.reset", "earliest");
   tmq_conf_set(conf, "experimental.snapshot.enable", "true");
   tmq_conf_set(conf, "msg.with.table.name", "true");
   tmq_conf_set_auto_commit_cb(conf, tmq_commit_cb_print, NULL);
@@ -131,7 +133,12 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
   return tmq;
 ```
 
-四、创建订阅主题列表
+上述配置中包括consumer group ID，如果多个 consumer 指定的 consumer group ID一样，则自动形成一个consumer group，共享消费进度。
+
+
+## 创建 topic 列表
+
+单个consumer支持同时订阅多个topic。
 
 ```sql
   tmq_list_t* topicList = tmq_list_new();
@@ -139,9 +146,7 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
   return topicList;
 ```
 
-单个consumer支持同时订阅多个topic。
-
-五、启动订阅并开始消费
+## 启动订阅并开始消费
 
 ```sql
   /* 启动订阅 */
@@ -151,9 +156,9 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
   /* 循环poll消息 */
   int32_t totalRows = 0;
   int32_t msgCnt = 0;
-  int32_t consumeDelay = 5000;
+  int32_t timeOut = 5000;
   while (running) {
-    TAOS_RES* tmqmsg = tmq_consumer_poll(tmq, consumeDelay);
+    TAOS_RES* tmqmsg = tmq_consumer_poll(tmq, timeOut);
     if (tmqmsg) {
       msgCnt++;
       totalRows += msg_process(tmqmsg);
@@ -190,7 +195,7 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
     int32_t*    length      = taos_fetch_lengths(msg);
     int32_t     precision   = taos_result_precision(msg);
     const char* tbName      = tmq_get_table_name(msg);
-	rows++; 
+    rows++; 
     taos_print_row(buf, row, fields, numOfFields);
     printf("row content from %s: %s\n", (tbName != NULL ? tbName : "null table"), buf);
   }
@@ -199,7 +204,7 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
 }
 ```
 
-五、结束消费
+## 结束消费
 
 ```sql
   /* 取消订阅 */
@@ -209,7 +214,7 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
   tmq_consumer_close(tmq);
 ```
 
-六、删除topic
+## 删除topic
 
 如果不再需要，可以删除创建topic，但注意：只有没有被订阅的topic才能别删除。
 
@@ -218,7 +223,7 @@ create topic topicName as select ts, c1, c2, c3 from tmqdb.stb where c1 > 1;
   drop topic topicName;
 ```
 
-七、状态查看
+## 状态查看
 
 1、topics：查询已经创建的topic
 

docs/zh/14-reference/11-docker/index.md

@@ -147,7 +147,7 @@ import (
     "fmt"
     "time"
 
-    _ "github.com/taosdata/driver-go/v2/taosSql"
+    _ "github.com/taosdata/driver-go/v3/taosSql"
 )
 
 type config struct {

include/libs/function/functionMgt.h

@@ -202,6 +202,7 @@ bool fmIsForbidStreamFunc(int32_t funcId);
 bool fmIsIntervalInterpoFunc(int32_t funcId);
 bool fmIsInterpFunc(int32_t funcId);
 bool fmIsLastRowFunc(int32_t funcId);
+bool fmIsReturnNotNullFunc(int32_t funcId);
 bool fmIsSelectValueFunc(int32_t funcId);
 bool fmIsSystemInfoFunc(int32_t funcId);
 bool fmIsImplicitTsFunc(int32_t funcId);

source/libs/executor/src/executorimpl.c

@@ -1437,7 +1437,8 @@ static void setExecutionContext(SOperatorInfo* pOperator, int32_t numOfOutput, u
   pAggInfo->groupId = groupId;
 }
 
-static void doUpdateNumOfRows(SResultRow* pRow, int32_t numOfExprs, const int32_t* rowCellOffset) {
+static void doUpdateNumOfRows(SqlFunctionCtx* pCtx, SResultRow* pRow, int32_t numOfExprs, const int32_t* rowCellOffset) {
+  bool returnNotNull = false;
   for (int32_t j = 0; j < numOfExprs; ++j) {
     struct SResultRowEntryInfo* pResInfo = getResultEntryInfo(pRow, j, rowCellOffset);
     if (!isRowEntryInitialized(pResInfo)) {
@@ -1447,6 +1448,15 @@ static void doUpdateNumOfRows(SResultRow* pRow, int32_t numOfExprs, const int32_
     if (pRow->numOfRows < pResInfo->numOfRes) {
       pRow->numOfRows = pResInfo->numOfRes;
     }
+
+    if (fmIsReturnNotNullFunc(pCtx[j].functionId)) {
+      returnNotNull = true;
+    }
+  }
+  // if all expr skips all blocks, e.g. all null inputs for max function, output one row in final result.
+  //  except for first/last, which require not null output, output no rows
+  if (pRow->numOfRows == 0 && !returnNotNull) {
+    pRow->numOfRows = 1;
   }
 }
 
@@ -1458,7 +1468,7 @@ int32_t finalizeResultRowIntoResultDataBlock(SDiskbasedBuf* pBuf, SResultRowPosi
   SFilePage*  page = getBufPage(pBuf, resultRowPosition->pageId);
   SResultRow* pRow = (SResultRow*)((char*)page + resultRowPosition->offset);
 
-  doUpdateNumOfRows(pRow, numOfExprs, rowCellOffset);
+  doUpdateNumOfRows(pCtx, pRow, numOfExprs, rowCellOffset);
   if (pRow->numOfRows == 0) {
     releaseBufPage(pBuf, page);
     return 0;
@@ -1514,7 +1524,7 @@ int32_t doCopyToSDataBlock(SExecTaskInfo* pTaskInfo, SSDataBlock* pBlock, SExprI
 
     SResultRow* pRow = (SResultRow*)((char*)page + pPos->pos.offset);
 
-    doUpdateNumOfRows(pRow, numOfExprs, rowCellOffset);
+    doUpdateNumOfRows(pCtx, pRow, numOfExprs, rowCellOffset);
     if (pRow->numOfRows == 0) {
       pGroupResInfo->index += 1;
       releaseBufPage(pBuf, page);

source/libs/function/src/builtinsimpl.c

@@ -64,6 +64,9 @@ typedef struct SMinmaxResInfo {
   bool      assign;  // assign the first value or not
   int64_t   v;
   STuplePos tuplePos;
+
+  STuplePos nullTuplePos;
+  bool      nullTupleSaved;
 } SMinmaxResInfo;
 
 typedef struct STopBotResItem {
@@ -75,6 +78,10 @@ typedef struct STopBotResItem {
 typedef struct STopBotRes {
   int32_t         maxSize;
   int16_t         type;
+
+  STuplePos       nullTuplePos;
+  bool            nullTupleSaved;
+
   STopBotResItem* pItems;
 } STopBotRes;
 
@@ -221,6 +228,10 @@ typedef struct SSampleInfo {
   int32_t    numSampled;
   uint8_t    colType;
   int16_t    colBytes;
+
+  STuplePos  nullTuplePos;
+  bool       nullTupleSaved;
+
   char*      data;
   STuplePos* tuplePos;
 } SSampleInfo;
@@ -1134,6 +1145,9 @@ bool minmaxFunctionSetup(SqlFunctionCtx* pCtx, SResultRowEntryInfo* pResultInfo)
   SMinmaxResInfo* buf = GET_ROWCELL_INTERBUF(pResultInfo);
   buf->assign = false;
   buf->tuplePos.pageId = -1;
+
+  buf->nullTupleSaved = false;
+  buf->nullTuplePos.pageId = -1;
   return true;
 }
 
@@ -1575,6 +1589,10 @@ int32_t doMinMaxHelper(SqlFunctionCtx* pCtx, int32_t isMinFunc) {
   }
 
 _min_max_over:
+  if (numOfElems == 0 && pCtx->subsidiaries.num > 0 && !pBuf->nullTupleSaved ) {
+    doSaveTupleData(pCtx, pInput->startRowIndex, pCtx->pSrcBlock, &pBuf->nullTuplePos);
+    pBuf->nullTupleSaved = true;
+  }
   return numOfElems;
 }
 
@@ -1615,7 +1633,7 @@ int32_t minmaxFunctionFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
   if (pEntryInfo->numOfRes > 0) {
     setSelectivityValue(pCtx, pBlock, &pRes->tuplePos, currentRow);
   } else {
-    setNullSelectivityValue(pCtx, pBlock, currentRow);
+    setSelectivityValue(pCtx, pBlock, &pRes->nullTuplePos, currentRow);
   }
 
   return pEntryInfo->numOfRes;
@@ -3366,6 +3384,8 @@ bool topBotFunctionSetup(SqlFunctionCtx* pCtx, SResultRowEntryInfo* pResInfo) {
 
   pRes->maxSize = pCtx->param[1].param.i;
 
+  pRes->nullTupleSaved = false;
+  pRes->nullTuplePos.pageId = -1;
   return true;
 }
 
@@ -3403,6 +3423,10 @@ int32_t topFunction(SqlFunctionCtx* pCtx) {
     doAddIntoResult(pCtx, data, i, pCtx->pSrcBlock, pRes->type, pInput->uid, pResInfo, true);
   }
 
+  if (numOfElems == 0 && pCtx->subsidiaries.num > 0 && !pRes->nullTupleSaved) {
+    doSaveTupleData(pCtx, pInput->startRowIndex, pCtx->pSrcBlock, &pRes->nullTuplePos);
+    pRes->nullTupleSaved = true;
+  }
   return TSDB_CODE_SUCCESS;
 }
 
@@ -3427,6 +3451,11 @@ int32_t bottomFunction(SqlFunctionCtx* pCtx) {
     doAddIntoResult(pCtx, data, i, pCtx->pSrcBlock, pRes->type, pInput->uid, pResInfo, false);
   }
 
+  if (numOfElems == 0 && pCtx->subsidiaries.num > 0 && !pRes->nullTupleSaved) {
+    doSaveTupleData(pCtx, pInput->startRowIndex, pCtx->pSrcBlock, &pRes->nullTuplePos);
+    pRes->nullTupleSaved = true;
+  }
+
   return TSDB_CODE_SUCCESS;
 }
 
@@ -3625,6 +3654,11 @@ int32_t topBotFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
 
   // todo assign the tag value and the corresponding row data
   int32_t currentRow = pBlock->info.rows;
+  if (pEntryInfo->numOfRes <= 0) {
+    colDataAppendNULL(pCol, currentRow);
+    setSelectivityValue(pCtx, pBlock, &pRes->nullTuplePos, currentRow);
+    return pEntryInfo->numOfRes;
+  }
   for (int32_t i = 0; i < pEntryInfo->numOfRes; ++i) {
     STopBotResItem* pItem = &pRes->pItems[i];
     if (type == TSDB_DATA_TYPE_FLOAT) {
@@ -4897,7 +4931,8 @@ bool sampleFunctionSetup(SqlFunctionCtx* pCtx, SResultRowEntryInfo* pResultInfo)
   pInfo->numSampled = 0;
   pInfo->colType = pCtx->resDataInfo.type;
   pInfo->colBytes = pCtx->resDataInfo.bytes;
-
+  pInfo->nullTuplePos.pageId = -1;
+  pInfo->nullTupleSaved = false;
   pInfo->data = (char*)pInfo + sizeof(SSampleInfo);
   pInfo->tuplePos = (STuplePos*)((char*)pInfo + sizeof(SSampleInfo) + pInfo->samples * pInfo->colBytes);
 
@@ -4943,6 +4978,11 @@ int32_t sampleFunction(SqlFunctionCtx* pCtx) {
     doReservoirSample(pCtx, pInfo, data, i);
   }
 
+  if (pInfo->numSampled == 0 && pCtx->subsidiaries.num > 0 && !pInfo->nullTupleSaved) {
+    doSaveTupleData(pCtx, pInput->startRowIndex, pCtx->pSrcBlock, &pInfo->nullTuplePos);
+    pInfo->nullTupleSaved = true;
+  }
+
   SET_VAL(pResInfo, pInfo->numSampled, pInfo->numSampled);
   return TSDB_CODE_SUCCESS;
 }
@@ -4957,6 +4997,11 @@ int32_t sampleFinalize(SqlFunctionCtx* pCtx, SSDataBlock* pBlock) {
   SColumnInfoData* pCol = taosArrayGet(pBlock->pDataBlock, slotId);
 
   int32_t currentRow = pBlock->info.rows;
+  if (pInfo->numSampled == 0) {
+    colDataAppendNULL(pCol, currentRow);
+    setSelectivityValue(pCtx, pBlock, &pInfo->nullTuplePos, currentRow);
+    return pInfo->numSampled;
+  }
   for (int32_t i = 0; i < pInfo->numSampled; ++i) {
     colDataAppend(pCol, currentRow + i, pInfo->data + i * pInfo->colBytes, false);
     setSelectivityValue(pCtx, pBlock, &pInfo->tuplePos[i], currentRow + i);

source/libs/function/src/functionMgt.c

@@ -221,6 +221,18 @@ bool fmIsLastRowFunc(int32_t funcId) {
   return FUNCTION_TYPE_LAST_ROW == funcMgtBuiltins[funcId].type;
 }
 
+bool fmIsReturnNotNullFunc(int32_t funcId) {
+  if (funcId < 0 || funcId >= funcMgtBuiltinsNum) {
+    return false;
+  }
+  return FUNCTION_TYPE_LAST == funcMgtBuiltins[funcId].type ||
+         FUNCTION_TYPE_LAST_PARTIAL == funcMgtBuiltins[funcId].type ||
+         FUNCTION_TYPE_LAST_MERGE == funcMgtBuiltins[funcId].type ||
+         FUNCTION_TYPE_FIRST == funcMgtBuiltins[funcId].type ||
+         FUNCTION_TYPE_FIRST_PARTIAL == funcMgtBuiltins[funcId].type ||
+         FUNCTION_TYPE_FIRST_MERGE == funcMgtBuiltins[funcId].type;
+}
+
 bool fmIsSelectValueFunc(int32_t funcId) {
   if (funcId < 0 || funcId >= funcMgtBuiltinsNum) {
     return false;

tests/docs-examples-test/go.sh

+#!/bin/bash
+
+set -e
+
+taosd >>/dev/null 2>&1 &
+taosadapter >>/dev/null 2>&1 &
+
+cd ../../docs/examples/go
+
+go mod tidy
+
+go run ./connect/afconn/main.go
+go run ./connect/cgoexample/main.go
+go run ./connect/restexample/main.go
+
+taos -s "drop database if exists test"
+go run ./insert/json/main.go
+taos -s "drop database if exists test"
+go run ./insert/line/main.go
+taos -s "drop database if exists power"
+go run ./insert/sql/main.go
+taos -s "drop database if exists power"
+go run ./insert/stmt/main.go
+taos -s "drop database if exists test"
+go run ./insert/telnet/main.go
+
+go run ./query/sync/main.go
+
+taos -s "drop topic if exists example_tmq_topic"
+taos -s "drop database if exists example_tmq"
+go run ./sub/main.go

tests/script/tsim/parser/function.sim

@@ -327,8 +327,8 @@ endi
 
 print =================>td-2610
 sql select stddev(k) from tm2 where ts='2020-12-29 18:46:19.109'
-if $rows != 0 then
-  print expect 0, actual:$rows
+if $rows != 1 then
+  print expect 1, actual:$rows
   return -1
 endi
 sql select twa(k) from tm2 where ts='2020-12-29 18:46:19.109'
@@ -406,7 +406,7 @@ if $data00 != 1.378704626 then
 endi
 
 sql select stddev(c) from m1
-if $rows != 0 then
+if $rows != 1 then
   return -1
 endi
 

tests/system-test/2-query/avg.py

@@ -295,7 +295,7 @@ class TDTestCase:
         tdSql.checkData(0, 0, 4.500000000)
 
         tdSql.query(f" select avg(c1) from {dbname}.stb1 where c1 is null ")
-        tdSql.checkRows(0)
+        tdSql.checkRows(1)
 
 
     def avg_func_filter(self, dbname="db"):

tests/system-test/2-query/distribute_agg_apercentile.py

@@ -86,7 +86,7 @@ class TDTestCase:
     def distribute_agg_query(self, dbname="testdb"):
         # basic filter
         tdSql.query(f"select apercentile(c1 , 20) from {dbname}.stb1 where c1 is null")
-        tdSql.checkRows(0)
+        tdSql.checkRows(1)
 
         tdSql.query(f"select apercentile(c1 , 20) from {dbname}.stb1 where t1=1")
         tdSql.checkData(0,0,2.800000000)

tests/system-test/2-query/distribute_agg_max.py

@@ -168,7 +168,7 @@ class TDTestCase:
     def distribute_agg_query(self, dbname="testdb"):
         # basic filter
         tdSql.query(f"select max(c1) from {dbname}.stb1 where c1 is null")
-        tdSql.checkRows(0)
+        tdSql.checkRows(1)
 
         tdSql.query(f"select max(c1) from {dbname}.stb1 where t1=1")
         tdSql.checkData(0,0,10)

tests/system-test/2-query/distribute_agg_min.py

@@ -167,7 +167,7 @@ class TDTestCase:
     def distribute_agg_query(self, dbname="testdb"):
         # basic filter
         tdSql.query(f"select min(c1) from {dbname}.stb1 where c1 is null")
-        tdSql.checkRows(0)
+        tdSql.checkRows(1)
 
         tdSql.query(f"select min(c1) from {dbname}.stb1 where t1=1")
         tdSql.checkData(0,0,2)

tests/system-test/2-query/distribute_agg_spread.py

@@ -195,7 +195,7 @@ class TDTestCase:
     def distribute_agg_query(self):
         # basic filter
         tdSql.query("select spread(c1) from stb1 where c1 is null")
-        tdSql.checkRows(0)
+        tdSql.checkRows(1)
 
         tdSql.query("select spread(c1) from stb1 where t1=1")
         tdSql.checkData(0,0,8.000000000)

tests/system-test/2-query/sample.py

@@ -743,7 +743,7 @@ class TDTestCase:
         # filter data
 
         tdSql.query(" select sample(c1, 20 ) from t1 where c1 is null ")
-        tdSql.checkRows(0)
+        tdSql.checkRows(1)
 
         tdSql.query(" select sample(c1, 20 ) from t1 where c1 =6 ")
         tdSql.checkRows(1)
@@ -891,4 +891,4 @@ class TDTestCase:
         tdLog.success("%s successfully executed" % __file__)
 
 tdCases.addWindows(__file__, TDTestCase())
-tdCases.addLinux(__file__, TDTestCase())
\ No newline at end of file
+tdCases.addLinux(__file__, TDTestCase())