未验证 提交 b60f5f8e 编写于 作者: W wade zhang 提交者: GitHub

Merge pull request #16502 from taosdata/docs/TD-18686

doc: correct wrong description about maximum SQL length
......@@ -16,7 +16,7 @@ To achieve high performance writing, there are a few aspects to consider. In the
From the perspective of application program, you need to consider:
1. The data size of each single write, also known as batch size. Generally speaking, higher batch size generates better writing performance. However, once the batch size is over a specific value, you will not get any additional benefit anymore. When using SQL to write into TDengine, it's better to put as much as possible data in single SQL. The maximum SQL length supported by TDengine is 1,048,576 bytes, i.e. 1 MB. It can be configured by parameter `maxSQLLength` on client side, and the default value is 65,480.
1. The data size of each single write, also known as batch size. Generally speaking, higher batch size generates better writing performance. However, once the batch size is over a specific value, you will not get any additional benefit anymore. When using SQL to write into TDengine, it's better to put as much as possible data in single SQL. The maximum SQL length supported by TDengine is 1,048,576 bytes, i.e. 1 MB.
2. The number of concurrent connections. Normally more connections can get better result. However, once the number of connections exceeds the processing ability of the server side, the performance may downgrade.
......@@ -356,7 +356,7 @@ Writing process tries to read as much as possible data from message queue and wr
<details>
SQLWriter class encapsulates the logic of composing SQL and writing data. Please be noted that the tables have not been created before writing, but are created automatically when catching the exception of table doesn't exist. For other exceptions caught, the SQL which caused the exception are logged for you to debug. This class also checks the SQL length, if the SQL length is closed to `maxSQLLength` the SQL will be executed immediately. To improve writing efficiency, it's better to increase `maxSQLLength` properly.
SQLWriter class encapsulates the logic of composing SQL and writing data. Please be noted that the tables have not been created before writing, but are created automatically when catching the exception of table doesn't exist. For other exceptions caught, the SQL which caused the exception are logged for you to debug. This class also checks the SQL length, and passes the maximum SQL length by parameter maxSQLLength according to actual TDengine limit.
<summary>SQLWriter</summary>
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......@@ -11,7 +11,7 @@ import TabItem from "@theme/TabItem";
从客户端程序的角度来说,高效写入数据要考虑以下几个因素:
1. 单次写入的数据量。一般来讲,每批次写入的数据量越大越高效(但超过一定阈值其优势会消失)。使用 SQL 写入 TDengine 时,尽量在一条 SQL 中拼接更多数据。目前,TDengine 支持的一条 SQL 的最大长度为 1,048,576(1M)个字符。可通过配置客户端参数 maxSQLLength(默认值为 65480)进行修改。
1. 单次写入的数据量。一般来讲,每批次写入的数据量越大越高效(但超过一定阈值其优势会消失)。使用 SQL 写入 TDengine 时,尽量在一条 SQL 中拼接更多数据。目前,TDengine 支持的一条 SQL 的最大长度为 1,048,576(1M)个字符。
2. 并发连接数。一般来讲,同时写入数据的并发连接数越多写入越高效(但超过一定阈值反而会下降,取决于服务端处理能力)。
3. 数据在不同表(或子表)之间的分布,即要写入数据的相邻性。一般来说,每批次只向同一张表(或子表)写入数据比向多张表(或子表)写入数据要更高效;
4. 写入方式。一般来讲:
......@@ -348,7 +348,7 @@ main 函数可以接收 5 个启动参数,依次是:
<details>
SQLWriter 类封装了拼 SQL 和写数据的逻辑。所有的表都没有提前创建,而是在发生表不存在错误的时候,再以超级表为模板批量建表,然后重新执行 INSERT 语句。对于其它错误会记录当时执行的 SQL, 以便排查错误和故障恢复。这个类也对 SQL 是否超过最大长度限制做了检查,如果接近 SQL 最大长度限制(maxSQLLength),将会立即执行 SQL。为了减少 SQL 此时,建议将 maxSQLLength 适当调大
SQLWriter 类封装了拼 SQL 和写数据的逻辑。所有的表都没有提前创建,而是在发生表不存在错误的时候,再以超级表为模板批量建表,然后重新执行 INSERT 语句。对于其它错误会记录当时执行的 SQL, 以便排查错误和故障恢复。这个类也对 SQL 是否超过最大长度限制做了检查,根据 TDengine 3.0 的限制由输入参数 maxSQLLength 传入了支持的最大 SQL 长度,即 1048576
<summary>SQLWriter</summary>
......
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