This topic describes the data types and parameters supported by MySQL Reader and how to configure it by using the codeless user interface (UI) and code editor.

MySQL Reader connects to a remote MySQL database through Java Database Connectivity (JDBC), generates a SELECT statement based on your configurations, and then sends the statement to the database. The MySQL database runs the statement and returns the result. Then, MySQL Reader assembles the returned data to abstract datasets in custom data types supported by Data Integration, and sends the datasets to a writer.

In short, MySQL Reader connects to a remote MySQL database and runs a SELECT statement to select and read data from the database.

MySQL Reader can read tables and views. For table fields, you can specify all or some of the columns in sequence, adjust the column order, specify constant fields, and configure MySQL functions, such as now().

Data types

The following table lists the data types supported by MySQL Reader.
Category MySQL data type
Integer INT, TINYINT, SMALLINT, MEDIUMINT, and BIGINT
Floating point FLOAT, DOUBLE, and DECIMAL
String VARCHAR, CHAR, TINYTEXT, TEXT, MEDIUMTEXT, and LONGTEXT
Date and time DATE, DATETIME, TIMESTAMP, TIME, and YEAR
Boolean BIT and BOOLEAN
Binary TINYBLOB, MEDIUMBLOB, BLOB, LONGBLOB, and VARBINARY
Note
  • Except for the preceding data types, other types are not supported.
  • MySQL Reader considers tinyint(1) as the INTEGER type.

Parameters

Parameter Description Required Default value
datasource The connection name. It must be identical to the name of the added connection. You can add connections in the code editor. Yes None
table The name of the table to be synchronized. You can select only one source table for each sync node. Yes None
column The columns to be synchronized from the source table. The columns are described in a JSON array. The default value is [ * ], which indicates all columns.
  • Column pruning is supported. You can select and export specific columns.
  • Change of the column order is supported. You can export the columns in an order different from that specified in the schema of the table.
  • Constants are supported. The column names must be arranged in compliance with the SQL syntax supported by MySQL, for example, ["id","table","1","'mingya.wmy'","'null'","to_char(a+1)","2.3","true"] .
    • id: a column name.
    • table: the name of a column that contains reserved keywords.
    • 1: an integer constant.
    • 'mingya.wmy': a string constant, which is enclosed in single quotation marks (' ').
    • null:
      • '' '' indicates an empty value.
      • null indicates a null value.
      • 'null' indicates the string null.
    • to_char(a+1): a function expression.
    • 2.3: a floating-point constant.
    • true: a Boolean value.
  • The column parameter must explicitly specify a set of columns to be synchronized. The parameter cannot be left empty.
Yes None
splitPk The field used for data sharding when MySQL Reader extracts data. If you specify the splitPk parameter, the table is sharded based on the shard key specified by this parameter. Data Integration then runs concurrent threads to synchronize data. This improves efficiency.
  • We recommend that you set the splitPk parameter to the primary key of the table. Based on the primary key, data can be well distributed to different shards, but not intensively distributed to certain shards.
  • Currently, the splitPk parameter supports data sharding only for integers but not for other data types such as string, floating point, and date. If you specify this parameter to a column of an unsupported type, MySQL Reader ignores the splitPk parameter and synchronizes data through a single thread.
  • If you do not specify the splitPk parameter or leave it empty, Data Integration synchronizes data through a single thread.
No None
where The WHERE clause. For example, set this parameter to gmt_create>$bizdate.
  • You can use the WHERE clause to synchronize incremental data. If you do not specify the where parameter or leave it empty, all data is synchronized.
  • Do not set the where parameter to limit 10, which does not conform to the constraints of MySQL on the SQL WHERE clause.
No None
querySql (only available in the code editor) The SELECT statement used for refined data filtering. If you specify this parameter, Data Integration directly filters data based on this parameter. For example, if you want to join multiple tables for data synchronization, set this parameter to select a,b from table_a join table_b on table_a.id = table_b.id. The priority of the querySql parameter is higher than those of the table, column, where, and splitPk parameters. If you specify the querySql parameter, MySQL Reader ignores the table, column, where, and splitPk parameters that you have configured. The datasource parameter parses information, including the username and password, from this parameter.
Note The querySql parameter is case-sensitive. For example, if you enter querysql, it does not take effect.
No None
singleOrMulti (only applicable to database and table sharding) Specifies whether to shard the database or table. After you switch from the codeless UI to the code editor, the following configuration is automatically generated: "singleOrMulti":"multi". However, if you use the code editor since the beginning, the configuration is not automatically generated and you must manually specify this parameter. If you do not specify this parameter or leave it empty, MySQL Reader can only read data from the first shard. Yes multi

Configure MySQL Reader by using the codeless UI

  1. Configure the connections.
    Configure the source and destination connections for the sync node.Connections
    Parameter Description
    Connection The datasource parameter in the preceding parameter description. Select a connection type, and enter the name of a connection that has been configured in DataWorks.
    Table The table parameter in the preceding parameter description.
    Filter The filter condition for the data to be synchronized. Currently, filtering based on the limit keyword is not supported. The SQL syntax is determined by the selected connection.
    Shard Key The shard key. You can use a column in the source table as the shard key. We recommend that you use the primary key or an indexed column. Only integer fields are supported.
    If data sharding is performed based on the configured shard key, data can be read concurrently to improve data synchronization efficiency.
    Note The Shard Key parameter appears only when you configure the source connection for a sync node.
  2. Configure field mapping, that is, 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. You can click Add to add a field or move the pointer over a field and click the Delete icon to delete the field.Mappings
    Parameter Description
    Map Fields with the Same Name Click Map Fields with the Same Name to establish a mapping between fields with the same name. Note that the data types of the fields must match.
    Fields in the Same Line Click Map Fields in the Same Line to establish a mapping for fields in the same row. Note that the data types of the fields must match.
    Delete All Mappings Click Delete All Mappings to remove mappings that have been established.
    Auto Layout Click Auto Layout. The fields are automatically sorted based on specified rules.
    Change Fields Click the Change Fields icon. In the Change Fields dialog box that appears, you can manually edit fields in the source table. Each field occupies a row. The first and the last blank rows are included, whereas other blank rows are ignored.
    Add
    • Click Add to add a field. You can enter constants. Each constant must be enclosed in single quotation marks (' '), such as 'abc' and '123'.
    • You can use scheduling parameters, such as ${bizdate}.
    • You can enter functions supported by relational databases, such as now() and count(1).
    • Fields that cannot be parsed are indicated by Unidentified.
  3. Configure channel control policies.Channel
    Parameter Description
    Expected Maximum Concurrency The maximum number of concurrent threads to read and write data to data storage within the sync node. You can configure the concurrency for a node on the codeless UI.
    Bandwidth Throttling 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.
    Dirty Data Records Allowed The maximum number of dirty data records allowed.
    Resource Group The resource group used for running the sync node. If a large number of nodes including this sync node are deployed on the default resource group, the sync node may need to wait for resources. We recommend that you purchase an exclusive resource group for data integration or add a custom resource group. For more information, see DataWorks exclusive resources and Add a custom resource group.

Configure MySQL Reader by using the code editor

In the following code, a node is configured to read data from a database or table that is not sharded. For more information about the parameters, see the preceding parameter description.
{
    "type":"job",
    "version":"2.0",// The version number.
    "steps":[
        {
            "stepType":"mysql",// The reader type.
            "parameter":{
                "column":[// The columns to be synchronized.
                    "id"
                ],
                "connection":[
                    {   "querySql":["select a,b from join1 c join join2 d on c.id = d.id;"], // Specify the querySql parameter in the connection parameter as a string.
                        "datasource":"",// The connection name.
                        "table":[// The name of the table to be synchronized. The table name must be enclosed in brackets ([ ]), even if only one table exists.
                            "xxx"
                        ]
                    }
                ],
                "where":"", // The WHERE clause.
                "splitPk":"",// The shard key.
                "encoding":"UTF-8"// The encoding format.
            },
            "name":"Reader",
            "category":"reader"
        },
        {// The following template is used to configure Stream Writer. For more information, see the corresponding topic.
            "stepType":"stream",
            "parameter":{},
            "name":"Writer",
            "category":"writer"
        }
    ],
    "setting":{
        "errorLimit":{
            "record":"0"// The maximum number of dirty data records allowed.
        },
        "speed":{
            "throttle":false,// Specifies whether to enable bandwidth throttling. A value of false indicates that the bandwidth is not throttled. A value of true indicates that the bandwidth is throttled. The maximum transmission rate takes effect only if you set this parameter to true.
            "concurrent":1,// The maximum number of concurrent threads.
        }
    },
    "order":{
        "hops":[
            {
                "from":"Reader",
                "to":"Writer"
            }
        ]
    }
}
In the following code, a node is configured to read data from a database or table that is sharded. For more information about the parameters, see the preceding parameter description.
Note In the case of database and table sharding, MySQL Reader can read multiple MySQL tables with the same schema.
{
    "type": "job",
    "version": "1.0",
    "Configuration ":{
        "reader": {
            "plugin": "mysql",
            "parameter": {
                "connection": [
                    {
                        "table": [
                            "tbl1",
                            "tbl2",
                            "tbl3"
                        ],
                        "datasource": "datasourceName1"
                    },
                    {
                        "table": [
                            "tbl4",
                            "tbl5",
                            "tbl6"
                        ],
                        "datasource": "datasourceName2"
                    }
                ],
                "singleOrMulti": "multi",
                "splitPk": "db_id",
                "column": [
                    "id", "name", "age"
                ],
                "where": "1 < id and id < 100"
            }
        },
        "writer": {            
        }
    }
}