This topic describes the data types and parameters that PolarDB Writer supports and how to configure it by using the codeless user interface (UI) and code editor.

PolarDB Writer allows you to write data to tables stored in PolarDB databases. Specifically, PolarDB Writer connects to a remote PolarDB database by using Java Database Connectivity (JDBC), and executes an INSERT INTO or REPLACE INTO statement to write data to the PolarDB database. Internally, data is submitted to the PolarDB database in batches by using the InnoDB engine.
Note You must configure a PolarDB connection before you configure PolarDB Writer. For more information, see Configure a PolarDB connection.
PolarDB Writer is designed for extract, transform, load (ETL) developers to import data from data warehouses to PolarDB databases. Users such as database administrators can use PolarDB Writer as a data migration tool. PolarDB Writer obtains data from a Data Integration reader, and writes the data to the destination database based on the writeMode parameter that you have configured.
Note A sync node that uses PolarDB Writer must have at least the permission to execute the INSERT INTO or REPLACE INTO statement. Whether other permissions are required depends on the SQL statements that you specify in the preSql and postSql parameters when you configure the node.

Data types

Similar to PolarDB Reader, PolarDB Writer supports most PolarDB data types. Make sure that your data types are supported.

The following table describes the data types that PolarDB Writer supports.
Category PolarDB 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 BOOL
Binary TINYBLOB, MEDIUMBLOB, BLOB, LONGBLOB, and VARBINARY

Parameters

Parameter Description Required Default value
datasource The connection name. It must be the same as the name of the added connection. You can add connections in the code editor. Yes N/A
table The name of the destination table. Yes N/A
writeMode The write mode. Valid values:
  • replace into: If no primary key conflict or unique index conflict occurs, the action is the same as that of insert into. If a conflict occurs, original rows are deleted and new rows are inserted.
  • insert into: If a primary key conflict or unique index conflict occurs, data cannot be written to the conflicting rows and is regarded as dirty data.
  • INSERT INTO table (a,b,c) VALUES (1,2,3) ON DUPLICATE KEY UPDATE: If no primary key conflict or unique index conflict occurs, the action is the same as that of insert into. If a conflict occurs, specified fields in original rows are updated.
No insert into
column The columns in the destination table to which data is written. Separate the columns with a comma (,), for example, "column":["id","name","age"]. Set the value to a space character if data needs to be written to all the columns in the destination table, for example, "column":[" "]. Yes N/A
preSql The SQL statement to execute before the sync node is run. For example, you can clear outdated data before data synchronization. You can execute only one SQL statement on the codeless UI and multiple SQL statements in the code editor. No N/A
postSql The SQL statement to execute after the sync node is run. For example, you can add a timestamp after data synchronization. You can execute only one SQL statement on the codeless UI and multiple SQL statements in the code editor. No N/A
batchSize The number of data records to write at a time. Set this parameter to a proper value based on your actual needs. This can greatly reduce the interactions between Data Integration and the PolarDB database on the network, and increase the throughput. However, an excessively large value may lead to the out of memory (OOM) error during the data synchronization process. No 1024

Configure PolarDB Writer by using the codeless UI

  1. Configure the connections.
    Configure the connections to the source and destination data stores for the sync node.Select data source section
    Parameter Description
    Data source The datasource parameter in the preceding parameter description. Select a connection type and select the name of a connection that you have configured in DataWorks.
    Table The table parameter in the preceding parameter description.
    Prepare statement before import The preSql parameter in the preceding parameter description. Enter an SQL statement to execute before the sync node is run.
    Complete statement after import The postSql parameter in the preceding parameter description. Enter an SQL statement to execute after the sync node is run. Example: update table set gmt_modify=now();.
    Primary key conflict The writeMode parameter in the preceding parameter description. Select the required write mode.
  2. Configure field mapping. It is equivalent to setting the column parameter in the preceding parameter description. Fields in the source table on the left have a one-to-one mapping with fields in the destination table on the right.Field Mapping section
    GUI element Description
    The same name mapping Click The same name mapping to establish a mapping between fields with the same name. Note that the data types of the fields must match.
    Peer mapping Click Peer mapping to establish a mapping between fields in the same row. Note that the data types of the fields must match.
    Unmap Click Unmap to remove mappings that have been established.
    Automatic typesetting Click Automatic typesetting to sort the fields based on specified rules.
  3. Configure channel control policies.Channel control section
    Parameter Description
    Maximum number of concurrent tasks expected The maximum number of concurrent threads that the sync node uses to read data from or write data to data stores. You can configure the concurrency for the node on the codeless UI.
    Synchronization rate Specifies whether to enable bandwidth throttling. You can enable bandwidth throttling and set a maximum transmission rate to avoid heavy read workload of the source. We recommend that you enable bandwidth throttling and set the maximum transmission rate to a proper value.
    The number of error records exceeds The maximum number of dirty data records allowed.

Configure PolarDB Writer by using the code editor

You can configure PolarDB Writer by using the code editor. For more information, see Create a sync node by using the code editor.

The following example shows how to configure a sync node to write data to a PolarDB database. For more information about the parameters, see the preceding parameter description.
{
    "type": "job",
    "steps": [
        {
            "parameter": {},
            "name": "Reader",
            "category": "reader"
        },
        {
            "parameter": {
                "postSql": [],// The SQL statement to execute after the sync node is run.
                "datasource": "test_005",// The connection name.
                "column": [// The columns to which data is written.
                    "id",
                    "name",
                    "age",
                    "sex",
                    "salary",
                    "interest"
                ],
                "writeMode": "insert",// The write mode.
                "batchSize": 256,// The number of data records to write at a time.
                "encoding": "UTF-8",// The encoding format.
                "table": "PolarDB_person_copy",// The name of the destination table.
                "preSql": []// The SQL statement to execute before the sync node is run.
            },
            "name": "Writer",
            "category": "writer"
        }
    ],
    "version": "2.0",// The version number.
    "order": {
        "hops": [
            {
                "from": "Reader",
                "to": "Writer"
            }
        ]
    },
    "setting": {
        "errorLimit": {// The maximum number of dirty data records allowed.
            "record": ""
        },
        "speed": {
            "concurrent": 6,// The number of concurrent threads.
            "throttle": false // Specifies whether to enable bandwidth throttling.
        }
    }
}