:DRDS Writer

DRDS Writer writes data to tables that are stored in Distributed Relational Database Service (DRDS) databases. DRDS Writer connects to the proxy of a remote DRDS database by using Java Database Connectivity (JDBC) and executes the REPLACE INTO statement to write data to the DRDS database.

DRDS Writer obtains data from a reader and executes the REPLACE INTO statement to write the data to the destination database. If no primary key conflict or unique index conflict occurs, data is directly written to the destination table, which is the same as the action of the INSERT INTO statement. If a conflict occurs, data in conflicting rows in the destination table is replaced by new data. DRDS Writer sends data to the DRDS proxy when the amount of buffered data reaches a specific threshold. The proxy determines whether to write the data to one or more tables and how to route the data when the data is written to multiple tables.

The following table lists the data types that are supported by DRDS Writer.

Category	DRDS data type
Integer	INT, TINYINT, SMALLINT, MEDIUMINT, BIGINT, and YEAR
Floating point	FLOAT, DOUBLE, and DECIMAL
String	VARCHAR, CHAR, TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT
Date and time	DATE, DATETIME, TIMESTAMP, and TIME
Boolean	BIT and BOOLEAN
Binary	TINYBLOB, MEDIUMBLOB, BLOB, LONGBLOB, and VARBINARY

Perform the following steps on the configuration tab of the node:

1. Configure data sources.
   Configure Source and Target for the synchronization node.

   Parameter	Description
   Connection	The name of the data source to which you want to write data. This parameter is equivalent to the datasource parameter that is described in the preceding section.
   Table	The name of the table to which you want to write data. This parameter is equivalent to the table parameter that is described in the preceding section.
   Statement Run Before Writing	The SQL statement that you want to execute before the synchronization node is run. This parameter is equivalent to the preSql parameter that is described in the preceding section.
   Statement Run After Writing	The SQL statement that you want to execute after the synchronization node is run. This parameter is equivalent to the postSql parameter that is described in the preceding section.
   Solution to Primary Key Violation	The write mode. This parameter is equivalent to the writeMode parameter that is described in the preceding section. You can select the desired write mode.

2. Configure field mappings. This operation is equivalent to setting the column parameter that is described in the preceding section. Fields in the source on the left have a one-to-one mapping with fields in the destination on the right.

   Operation	Description
   Map Fields with the Same Name	Click Map Fields with the Same Name to establish mappings between fields with the same name. The data types of the fields must match.
   Map Fields in the Same Line	Click Map Fields in the Same Line to establish mappings between fields in the same row. The data types of the fields must match.
   Delete All Mappings	Click Delete All Mappings to remove the mappings that are established.
   Auto Layout	Click Auto Layout. Then, the system automatically sorts the fields based on specific rules.

3. Configure channel control policies.

   Parameter	Description
   Expected Maximum Concurrency	The maximum number of parallel threads that the synchronization node uses to read data from the source or write data to the destination. You can configure the parallelism for the synchronization node on the codeless UI.
   Bandwidth Throttling	Specifies whether to enable bandwidth throttling. You can enable bandwidth throttling and specify a maximum transmission rate to prevent heavy read workloads on the source. We recommend that you enable bandwidth throttling and set the maximum transmission rate to an appropriate value based on the configurations of the source.
   Dirty Data Records Allowed	The maximum number of dirty data records allowed.

In the following code, a synchronization node is configured to write data to a DRDS database. For more information about how to configure a synchronization node by using the code editor, see Create a sync node by using the code editor.

{
    "type":"job",
    "version":"2.0",// The version number. 
    "steps":[
        {
            "stepType":"stream",
            "parameter":{},
            "name":"Reader",
            "category":"reader"
                },
        {
            "stepType":"drds",// The writer type. 
            "parameter":{
                "postSql":[],// The SQL statement that you want to execute after the synchronization node is run. 
                "datasource":"",// The name of the data source. 
                "column":[// The names of the columns to which you want to write data. 
                "id"
                ],
                "writeMode":"insert ignore",
                "batchSize":"1024",// The number of data records to write at a time. 
                "table":"test",// The name of the table to which you want to write data. 
                "preSql":[]// The SQL statement that you want to execute before the synchronization node is run. 
                },
            "name":"Writer",
            "category":"writer"
                }
                ],
    "setting":{
        "errorLimit":{
        "record":"0"// The maximum number of dirty data records allowed. 
            },
        "speed":{
            "throttle":true,// Specifies whether to enable bandwidth throttling. The value false indicates that bandwidth throttling is disabled, and the value true indicates that bandwidth throttling is enabled. The mbps parameter takes effect only when the throttle parameter is set to true. 
            "concurrent":1, // The maximum number of parallel threads. 
            "mbps":"12"// The maximum transmission rate.
                }
            },
    "order":{
        "hops":[
            {
                "from":"Reader",
                "to":"Writer"
                }
            ]
        }
    }