[FLINK-28345] Flink JDBC connector should check batch count before flush

• Type: Improvement
• Status: Closed
• Priority: Major
• Resolution: Won't Fix
• Affects Version/s: 1.14.5, 1.15.0
• Component/s: Connectors / JDBC
• Assignee: Unassigned
• Reporter: Feng Jin
• Created: 01/Jul/22 08:37
• Updated: 05/Jul/22 11:25
• Resolved: 05/Jul/22 11:25

Description

org.apache.flink.connector.jdbc.internal.JdbcOutputFormat#flush

//代码占位符
@Override
public synchronized void flush() throws IOException {
    checkFlushException();

    for (int i = 0; i <= executionOptions.getMaxRetries(); i++) {
        try {
            attemptFlush();
            batchCount = 0;
            break; 
   ....

When flush the batch,  we should check batchCount  is grater than 0. Other wise it would cause some problem with some drivers that do not support empty batches, like clickhouse jdbc driver.