flink-1.12.0 流模式 使用 lag问题

如何使用才是正确的，求大佬帮看看

behavior,next_bv 字段内容一直是保持一致的，无法得到自己想要的结果

发送的数据

{

  "user_id": 1,

  "item_id": 1,

  "behavior":"pv1"

}

{

  "user_id": 1,

  "item_id": 1,

  "behavior":"pv2"

}

CREATE TABLE KafkaTable (

  user_id BIGINT,

  item_id BIGINT,

  behavior STRING,

  proctime as PROCTIME()

) WITH (

  'connector' = 'kafka',

  'topic' = 'user_behavior',

  'properties.bootstrap.servers' = '',

  'properties.group.id' = 'testGroup',

  'scan.startup.mode' = 'earliest-offset',

  'format' = 'json'

);

SELECT

user_id,

item_id,

behavior,

next_bv 

FROM

( SELECT *, lag( behavior, 1 ) over ( PARTITION BY user_id ORDER BY proctime ) AS next_bv FROM KafkaTable ) t;*来自志愿者整理的flink邮件归档