DataWorks:SQL Server data source

Supported SQL Server versions

SQL Server Reader uses the driver com.microsoft.sqlserver sqljdbc4 4.0. For more information about the capabilities of the driver, see the official documentation. The following table lists the commonly used SQL Server versions and describes whether they are supported by the driver.

Limits

Data of views can be read during batch synchronization.

Data types

The following table lists the data type mappings based on which SQL Server Reader and SQL Server Writer converts data types.

Develop a data synchronization task

For information about the entry point for and the procedure of configuring a data synchronization task, see the following sections. For information about the parameter settings, view the infotip of each parameter on the configuration tab of the task.

Add a data source

Before you configure a data synchronization node to synchronize data from or to a specific data source, you must add the data source to DataWorks. For more information, see Add and manage data sources.

Configure a batch synchronization task to synchronize data of a single table

• For more information about the configuration procedure, see Configure a batch synchronization task by using the codeless UI and Configure a batch synchronization task by using the code editor.

• For information about all parameters that are configured and the code that is run when you use the code editor to configure a batch synchronization task, see Appendix: Code and parameters.

Configure synchronization settings to implement batch synchronization of all data in a database

For more information about the configuration procedure, see Configure a synchronization task in Data Integration.

Additional information

• Data synchronization between primary and secondary databases

  A secondary SQL Server database can be deployed for disaster recovery. The secondary database continuously synchronizes data from the primary database based on binary logs. Data latency between the primary and secondary databases cannot be prevented. This may result in data inconsistency.

• Data consistency control

  SQL Server is a relational database management system (RDBMS) that supports strong consistency for data queries. A database snapshot is created before a synchronization task starts. SQL Server Reader reads data from the database snapshot. Therefore, if new data is written to the database during data synchronization, SQL Server Reader cannot obtain the new data.

  Data consistency cannot be ensured if you enable SQL Server Reader to use parallel threads to read data in a synchronization task.

  SQL Server Reader shards the source table based on the value of the splitPk parameter and uses parallel threads to read data. These parallel threads belong to different transactions and read data at different points in time. Therefore, the parallel threads observe different snapshots.

  Data inconsistencies cannot be prevented if parallel threads are used for a synchronization task. The following workarounds can be used:

  • Enable SQL Server Reader to use a single thread to read data in a synchronization task. This indicates that you do not need to specify a shard key for SQL Server Reader. This way, data consistency is ensured, but data is synchronized at low efficiency.

  • Make sure that no data is written to the source table during data synchronization. This ensures that the data in the source table remains unchanged during data synchronization. For example, you can lock the source table or disable data synchronization between primary and secondary databases. This way, data is efficiently synchronized, but your ongoing services may be interrupted.

• Character encoding

  SQL Server Reader uses JDBC to read data. This enables SQL Server Reader to automatically convert the encoding formats of characters. Therefore, you do not need to specify the encoding format.

• Incremental data synchronization

  SQL Server Reader uses JDBC to connect to a database and uses a SELECT statement with a WHERE clause to read incremental data.

  • For batch data, incremental add, update, and delete operations (including logically delete operations) are distinguished by timestamps. Specify the WHERE clause based on a specific timestamp. The time indicated by the timestamp must be later than the time indicated by the latest timestamp in the previous synchronization.

  • For streaming data, specify the WHERE clause based on the ID of a specific record. The ID must be greater than the maximum ID involved in the previous synchronization.

  If the data that is added or modified cannot be distinguished, SQL Server Reader can read only full data.

• Syntax validation

  SQL Server Reader allows you to specify custom SELECT statements by using the querySql parameter but does not verify the syntax of these statements.

Appendix: Code and parameters

Appendix: Configure a batch synchronization task by using the code editor

If you use the code editor to configure a batch synchronization node, you must configure parameters for the reader and writer of the related data source based on the format requirements in the code editor. For more information about the format requirements, see Configure a batch synchronization node by using the code editor. The following information describes the configuration details of parameters for the reader and writer in the code editor.

Code for SQL Server Reader

{
    "type":"job",
    "version":"2.0",// The version number. 
    "steps":[
        {
            "stepType":"sqlserver",// The plug-in name. 
            "parameter":{
                "datasource":"",// The name of the data source. 
                "column":[// The names of the columns. 
                    "id",
                    "name"
                ],
                "where":"",// The WHERE clause. 
                "splitPk":"",// The shard key based on which the table is sharded. 
                "table":""// The name of the table. 
            },
            "name":"Reader",
            "category":"reader"
        },
        {
            "stepType":"stream",
            "parameter":{},
            "name":"Writer",
            "category":"writer"
        }
    ],
    "setting":{
        "errorLimit":{
            "record":"0"// The maximum number of dirty data records allowed. 
        },
        "speed":{
            "throttle":true,// Specifies whether to enable throttling. The value false indicates that throttling is disabled, and the value true indicates that 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. Unit: MB/s. 
        }
    },
    "order":{
        "hops":[
            {
                "from":"Reader",
                "to":"Writer"
            }
        ]
    }
}

{
    "stepType": "sqlserver",
    "parameter": {
        "querySql": "select name from dbo.test_table",
        "datasource": "sql_server_source",
        "column": [
            "name"
        ],
        "where": "",
        "splitPk": "id"
    },
    "name": "Reader",
    "category": "reader"
},

Parameters in code for SQL Server Reader

Code for SQL Server Writer

{
    "type":"job",
    "version":"2.0",// The version number. 
    "steps":[
        {
            "stepType":"stream",
            "parameter":{},
            "name":"Reader",
            "category":"reader"
        },
        {
            "stepType":"sqlserver",// The plug-in name. 
            "parameter":{
                "postSql":[],// The SQL statement that you want to execute after the synchronization task is run. 
                "datasource":"",// The name of the data source. 
                "column":[// The names of the columns. 
                    "id",
                    "name"
                ],
                "table":"",// The name of the table. 
                "preSql":[]// The SQL statement that you want to execute before the synchronization task 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 throttling. The value false indicates that throttling is disabled, and the value true indicates that 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. Unit: MB/s. 
        }
    },
    "order":{
        "hops":[
            {
                "from":"Reader",
                "to":"Writer"
            }
        ]
    }
}

Parameters in code for SQL Server Writer