JDBC Source Table

Function

The JDBC connector is a Flink's built-in connector to read data from a database.

Prerequisites

• An enhanced datasource connection with the instances has been established, so that you can configure security group rules as required.

Precautions

When creating a Flink OpenSource SQL job, you need to set Flink Version to 1.12 on the Running Parameters tab of the job editing page, select Save Job Log, and set the OBS bucket for saving job logs.

Syntax

create table jbdcSource (
  attr_name attr_type 
  (',' attr_name attr_type)* 
  (','PRIMARY KEY (attr_name, ...) NOT ENFORCED)
  (',' watermark for rowtime_column_name as watermark-strategy_expression)
) with (
  'connector' = 'jdbc',
  'url' = '',
  'table-name' = '',
  'username' = '',
  'password' = ''
);

Parameters

Partitioned Scan

To accelerate reading data in parallel Source task instances, Flink provides the partitioned scan feature for the JDBC table. The following parameters describe how to partition the table when reading in parallel from multiple tasks.

• scan.partition.column: name of the column used to partition the input. The data type of the column must be number, date, or timestamp.
• scan.partition.num: number of partitions.
• scan.partition.lower-bound: minimum value of the first partition.
• scan.partition.upper-bound: maximum value of the last partition.

• When a table is created, the preceding partitioned scan parameters must all be specified if any of them is specified.
• The scan.partition.lower-bound and scan.partition.upper-bound parameters are used to decide the partition stride instead of filtering rows in the table. All rows in the table are partitioned and returned.

Data Type Mapping

Example

This example uses JDBC as the data source and Print as the sink to read data from the RDS MySQL database and write the data to the Print result table.

1. Create an enhanced datasource connection in the VPC and subnet where RDS MySQL locates, and bind the connection to the required Flink elastic resource pool.
2. Set RDS MySQL security groups and add inbound rules to allow access from the Flink queue. Test the connectivity using the RDS address. If the connection is successful, the datasource is bound to the queue. Otherwise, the binding fails.
3. Log in to the RDS MySQL database, create table orders in the Flink database, and insert data.

   Create table orders in the Flink database.

   CREATE TABLE `flink`.`orders` (
   	`order_id` VARCHAR(32) NOT NULL,
   	`order_channel` VARCHAR(32) NULL,
   	`order_time` VARCHAR(32) NULL,
   	`pay_amount` DOUBLE UNSIGNED NOT NULL,
   	`real_pay` DOUBLE UNSIGNED NULL,
   	`pay_time` VARCHAR(32) NULL,
   	`user_id` VARCHAR(32) NULL,
   	`user_name` VARCHAR(32) NULL,
   	`area_id` VARCHAR(32) NULL,
   	PRIMARY KEY (`order_id`)
   )	ENGINE = InnoDB
   	DEFAULT CHARACTER SET = utf8mb4
   	COLLATE = utf8mb4_general_ci;

   Insert data into the table.

   insert into orders(
     order_id,
     order_channel,
     order_time,
     pay_amount,
     real_pay,
     pay_time,
     user_id,
     user_name,
     area_id) values
     ('202103241000000001', 'webShop', '2021-03-24 10:00:00', '100.00', '100.00', '2021-03-24 10:02:03', '0001', 'Alice', '330106'),  
     ('202103251202020001', 'miniAppShop', '2021-03-25 12:02:02', '60.00', '60.00', '2021-03-25 12:03:00', '0002', 'Bob', '330110');

4. Create a Flink OpenSource SQL job. Enter the following job script and submit the job.
   When you create a job, set Flink Version to 1.12 on the Running Parameters tab. Select Save Job Log, and specify the OBS bucket for saving job logs. Change the values of the parameters in bold as needed in the following script.

   CREATE TABLE jdbcSource (
     order_id string,
     order_channel string,
     order_time string,
     pay_amount double,
     real_pay double,
     pay_time string,
     user_id string,
     user_name string,
     area_id string
   ) WITH (
     'connector' = 'jdbc',
     'url' = 'jdbc:mysql://MySQLAddress:MySQLPort/flink',--flink is the database name created in RDS MySQL.
     'table-name' = 'orders',
     'username' = 'MySQLUsername',
     'password' = 'MySQLPassword'
   );
   
   CREATE TABLE printSink (
     order_id string,
     order_channel string,
     order_time string,
     pay_amount double,
     real_pay double,
     pay_time string,
     user_id string,
     user_name string,
     area_id string
   ) WITH (
     'connector' = 'print'
   );
   
   insert into printSink select * from jdbcSource;

5. Perform the following operations to view the data result in the taskmanager.out file:
   1. Log in to the DLI console. In the navigation pane, choose Job Management > Flink Jobs.
   2. Click the name of the corresponding Flink job, choose Run Log, click OBS Bucket, and locate the folder of the log you want to view according to the date.
   3. Go to the folder of the date, find the folder whose name contains taskmanager, download the taskmanager.out file, and view result logs.

   The data result is as follows:

   +I(202103241000000001,webShop,2021-03-24 10:00:00,100.0,100.0,2021-03-24 10:02:03,0001,Alice,330106)
   +I(202103251202020001,miniAppShop,2021-03-25 12:02:02,60.0,60.0,2021-03-25 12:03:00,0002,Bob,330110)

FAQ

None