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摘要

很多时候flink消费上游kafka的数据是有重复的，因此有时候我们想数据在落盘之前进行去重，这在实际开发中具有广泛的应用场景，此处不说详细代码，只粘贴相应的flinksql

代码

--********************************************************************--
-- 创建临时表(只在当前sessoin生效的表称为临时表) DDL
CREATE TEMPORARY TABLE UserAttrSource ( `data` string,`kafkaMetaTimestamp` TIMESTAMP(3) METADATA FROM 'timestamp', -- kafka record携带的源数据时间戳，参考官网kafka connectorproctime as PROCTIME() -- 获取数据处理时间，这是flink内置支持的关键字
) WITH ('connector' = 'kafka','topic' = 'user_attri_ad_dirty_data','properties.bootstrap.servers' = 'kafka地址','scan.startup.mode' = 'timestamp', -- kafka扫描数据模式，参考官网kafka connector'scan.startup.timestamp-millis' ='1687305600000' , -- 2023-06-21 08:00:00'format' = 'raw' -- 意思是将kafka数据格式化为string
);-- 创建SINK 表
CREATE TEMPORARY TABLE ADB (log_date DATE,`errorType` int,appId string,`errorCode` int,`errorReason` string,`deserialization` string,`originalData` string,kafkaMetaTimestamp TIMESTAMP,data_hash string,PRIMARY KEY (`data_hash`) NOT ENFORCED
)
WITH ('connector' = 'adb3.0','url' = 'jdbc:mysql://xxxx:3306/flink_data?rewriteBatchedStatements=true','tableName' = 'usr_attr_dirty', 'userName'='username','password'='password'
);
-- 去重视图， 这是关键（json_value是flink的内置函数，data_hash是数据本身的primary key）
-- 下述语句含义是：根据data_hash字段分组，按照处理时间排序，取出最新的一条数据，其他的重复数据将被抛弃
CREATE TEMPORARY VIEW quchong ASSELECT data,kafkaMetaTimestamp FROM (SELECT *,ROW_NUMBER() OVER (PARTITION BY json_value(data,'$.data_hash') ORDER BY proctime DESC) as row_numFROM UserAttrSource)WHERE row_num = 1;--  插入目标表
insert into ADB
select TO_DATE(DATE_FORMAT(kafkaMetaTimestamp,'yyyy-MM-dd') )AS log_date,json_value(data,'$.errorType' RETURNING INT) errorType,json_value(data,'$.appId' NULL ON EMPTY) appId,json_value(data,'$.errorCode'  RETURNING INT) errorCode,json_value(data,'$.errorReason' NULL ON EMPTY) errorReason,json_value(data,'$.deserialization' NULL ON EMPTY) deserialization,json_value(data,'$.originalData') originalData,kafkaMetaTimestamp,json_value(data,'$.data_hash') data_hash
from quchong;