为什么 Kafka jdbc 将插入数据作为 BLOB 而不是 var

本文介绍了为什么 Kafka jdbc 将插入数据作为 BLOB 而不是 varchar 连接的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！

问题描述

我正在使用 Java 生成器在我的 Kafka 主题顶部插入数据.然后我使用 Kafka jdbc connect 将数据插入到我的 Oracle 表中.下面是我的生产者代码.

I am using a Java producer to insert data top my Kafka topic. Then I use Kafka jdbc connect to insert data into my Oracle table. Below is my producer code.

package producer.serialized.avro;

import org.apache.avro.Schema;
import org.apache.avro.generic.GenericData;
import org.apache.avro.generic.GenericRecord;
import org.apache.kafka.clients.producer.KafkaProducer;
import org.apache.kafka.clients.producer.ProducerConfig;
import org.apache.kafka.clients.producer.ProducerRecord;

import java.util.Properties;


public class Sender4 {

    public static void main(String[] args) {

        String flightSchema = "{\"type\":\"record\"," + "\"name\":\"Flight\","

                + "\"fields\":[{\"name\":\"flight_id\",\"type\":\"string\"},{\"name\":\"flight_to\",\"type\":\"string\"},{\"name\":\"flight_from\",\"type\":\"string\"}]}";                

        Properties props = new Properties();

        props.put(ProducerConfig.BOOTSTRAP_SERVERS_CONFIG, "192.168.0.1:9092");
        props.put(ProducerConfig.KEY_SERIALIZER_CLASS_CONFIG,io.confluent.kafka.serializers.KafkaAvroSerializer.class);
        props.put(ProducerConfig.VALUE_SERIALIZER_CLASS_CONFIG,io.confluent.kafka.serializers.KafkaAvroSerializer.class);    
        props.put("schema.registry.url", "http://192.168.0.1:8081");            

        KafkaProducer producer = new KafkaProducer(props);    

        Schema.Parser parser = new Schema.Parser();

        Schema schema = parser.parse(flightSchema);            

        GenericRecord avroRecord = new GenericData.Record(schema);

        avroRecord.put("flight_id", "myflight");
        avroRecord.put("flight_to", "QWE");
        avroRecord.put("flight_from", "RTY");    

        ProducerRecord<String, GenericRecord> record = new ProducerRecord<>("topic9",avroRecord);

        producer.send(record);
    }
}


下面是我的 Kafka 连接属性
Below is my Kafka connect properties 
name=test-sink-6
connector.class=io.confluent.connect.jdbc.JdbcSinkConnector
tasks.max=1
topics=topic9
connection.url=jdbc:oracle:thin:@192.168.0.1:1521:usera
connection.user=usera
connection.password=usera
auto.create=true
table.name.format=FLIGHTS4
key.converter=io.confluent.connect.avro.AvroConverter
key.converter.schema.registry.url=http://192.168.0.1:8081
value.converter=io.confluent.connect.avro.AvroConverter
value.converter.schema.registry.url=http://192.168.0.1:8081

根据我的架构，我希望插入到我的 Oracle 表中的值是 varchar2.我创建了一个包含 3 个 varchar2 列的表.当我启动我的连接器时，没有插入任何东西.然后我删除了表并在表自动创建模式下运行连接器.那个时候，表被创建并且值被插入.但问题是，列数据类型是 CLOB.我希望它是 varchar2，因为它使用的数据较少.
From my schema, I am expecting the values inserted to my Oracle table to be varchar2. I have created a table having 3 varchar2 columns. When i started my connector, nothing got inserted. Then i deleted the table and ran the connector with table auto create mode on. That time, the table got created and values got inserted. But the problem is, the column data type is CLOB. I want it to be varchar2 since it use less data.
为什么会发生这种情况，我该如何解决?谢谢你.
Why is this happening and how can i fix this? Thank you. 
推荐答案
貌似Kafka的String映射到Oracle的NCLOB:
Looks like Kafka's String is mapped to Oracle's NCLOB:



<table border="1">
<tr>
<th>Schema Type</th><th>MySQL</th><th>Oracle</th><th>PostgreSQL</th><th>SQLite</th>
</tr>
<tr>
<td>INT8</td><td>TINYINT</td><td>NUMBER(3,0)</td><td>SMALLINT</td><td>NUMERIC</td>
</tr>
<tr>
<td>INT16</td><td>SMALLINT</td><td>NUMBER(5,0)</td><td>SMALLINT</td><td>NUMERIC</td>
</tr>
<tr>
<td>INT32</td><td>INT</td><td>NUMBER(10,0)</td><td>INT</td><td>NUMERIC</td>
</tr>
<tr>
<td>INT64</td><td>BIGINT</td><td>NUMBER(19,0)</td><td>BIGINT</td><td>NUMERIC</td>
</tr>
<tr>
<td>FLOAT32</td><td>FLOAT</td><td>BINARY_FLOAT</td><td>REAL</td><td>REAL</td>
</tr>
<tr>
<td>FLOAT64</td><td>DOUBLE</td><td>BINARY_DOUBLE</td><td>DOUBLE PRECISION</td><td>REAL</td>
</tr>
<tr>
<td>BOOLEAN</td><td>TINYINT</td><td>NUMBER(1,0)</td><td>BOOLEAN</td><td>NUMERIC</td>
</tr>
<tr>
<td>STRING</td><td>VARCHAR(256)</td><td>NCLOB</td><td>TEXT</td><td>TEXT</td>
</tr>
<tr>
<td>BYTES</td><td>VARBINARY(1024)</td><td>BLOB</td><td>BYTEA</td><td>BLOB</td>
</tr>
<tr>
<td>'Decimal'</td><td>DECIMAL(65,s)</td><td>NUMBER(*,s)</td><td>DECIMAL</td><td>NUMERIC</td>
</tr>
<tr>
<td>'Date'</td><td>DATE</td><td>DATE</td><td>DATE</td><td>NUMERIC</td>
</tr>
<tr>
<td>'Time'</td><td>TIME(3)</td><td>DATE</td><td>TIME</td><td>NUMERIC</td>
</tr>
<tr>
<td>'Timestamp'</td><td>TIMESTAMP(3)</td><td>TIMESTAMP</td><td>TIMESTAMP</td><td>NUMERIC</td>
</tr>
</table>



来源:https://www.ibm.com/support/knowledgecenter/en/SSPT3X_4.2.5/com.ibm.swg.im.infosphere.biginsights.admin.doc/doc/admin_kafka_jdbc_sink.html
https://docs.confluent.io/current/connect/connect-jdbc/docs/sink_connector.html
更新

OracleDialect 类(https://github.com/confluentinc/kafka-connect-jdbc/blob/master/src/main/java/io/confluent/connect/jdbc/sink/dialect/OracleDialect.java) 具有硬编码的 CLOB 值，只需使用您自己的类扩展它，更改映射将无济于事，因为方言类型是在 CLOB 中的静态方法中定义的代码>JdbcSinkTask (https://github.com/confluentinc/kafka-connect-jdbc/blob/master/src/main/java/io/confluent/connect/jdbc/sink/JdbcSinkTask.java)

OracleDialect class (https://github.com/confluentinc/kafka-connect-jdbc/blob/master/src/main/java/io/confluent/connect/jdbc/sink/dialect/OracleDialect.java) has hardcoded CLOB value and simply extend it with your own class and change that mapping will not help as type of dialect is defined in static method in JdbcSinkTask (https://github.com/confluentinc/kafka-connect-jdbc/blob/master/src/main/java/io/confluent/connect/jdbc/sink/JdbcSinkTask.java)

final DbDialect dbDialect = DbDialect.fromConnectionString(config.connectionUrl);

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为什么 Kafka jdbc 将插入数据作为 BLOB 而不是 var

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