Kafka SQL (KSQL)流不适用于包含嵌套字段的JSON数据

Question

我正在尝试用KSQL在Kafka主题之上创建一个Kafka流。我有如下的JSON记录存储在Kafka主题中。

{ "venue": { "venue_name": "HATCH", "lon": -71.18291, "lat": 42.36667, "venue_id": 22491322 }, "visibility": "public", "response": "yes", "guests": 0, "member": { "member_id": 237655942, "member_name": "Nts" }, "rsvp_id": 1724941595, "mtime": 1524620970613, "event": { "event_name": "Intro to Soldering", "event_id": "250106100", "time": 1526853600000, "event_url": "https:\/\/www.meetup.com\/Makers-of-HATCH-Makerspace\/events\/250106100\/" }, "group": { "group_topics": [ { "urlkey": "quilting", "topic_name": "Quilting" }, { "urlkey": "robotics", "topic_name": "Robotics" }, { "urlkey": "sewing", "topic_name": "Sewing" }, { "urlkey": "edtech", "topic_name": "Education & Technology" }, { "urlkey": "craftswap", "topic_name": "Crafts" }, { "urlkey": "diy", "topic_name": "DIY (Do It Yourself)" }, { "urlkey": "hacking", "topic_name": "Hacking" }, { "urlkey": "3d-modeling", "topic_name": "3D Modeling" }, { "urlkey": "tools", "topic_name": "Tools" }, { "urlkey": "arduino", "topic_name": "Arduino" }, { "urlkey": "makers", "topic_name": "Makers" }, { "urlkey": "makerspaces", "topic_name": "Makerspaces" }, { "urlkey": "3d-printing", "topic_name": "3D Printing" }, { "urlkey": "laser-cutting", "topic_name": "Laser Cutting" }, { "urlkey": "scrapbook-die-cutting-machines", "topic_name": "Scrapbook die cutting machines." } ], "group_city": "Watertown", "group_country": "us", "group_id": 18457932, "group_name": "Makers of HATCH Makerspace", "group_lon": -71.18, "group_urlname": "Makers-of-HATCH-Makerspace", "group_state": "MA", "group_lat": 42.37 } }

此数据已加载到Kafka主题中。

我已经在KSQL中创建了一个流，如下所示。

CREATE STREAM meetup_rsvp_raw 
(  Venue varchar, 
   Visibility varchar, 
   Response varchar, 
   Guests integer, 
   Member varchar, 
   rsvp_id bigint, 
   mtime bigint, 
   event varchar, 
   group_info varchar 
) WITH (KAFKA_TOPIC='meetup-rsvp', VALUE_FORMAT='JSON');

我在group_info( kafka流中的最后一个字段)字段中看到了null。注意: Kafka没有让我创建一个名称为"group“的字段，因为它是一个关键字。因此将该字段命名为group_info。

ksql> select * from meetup_rsvp_raw limit 2;

1524624181126 | null | {"venue_name":"Houghton's Pond - Blue Hills","lon":-71.09453,"lat":42.208187,"venue_id":1506300} | public | yes | 0 | {"member_id":159617162,"photo":"https://secure.meetupstatic.com/photos/member/7/2/b/c/thumb_215729372.jpeg","member_name":"Tena Kerns"} | 1724949934 | 1524623875376 | {"event_name":"Blue Hills Buck Hill - Easy Pace / Moderate hike","event_id":"250084062","time":1525010400000,"event_url":"https://www.meetup.com/HikeBikeSocialClub/events/250084062/"} | null

1524624181126 | null | {"venue_name":"Community Wholeness Centre CWC","lon":-79.69191,"lat":44.38976,"venue_id":19966962} | public | no | 0 | {"member_id":222279178,"photo":"https://secure.meetupstatic.com/photos/member/d/3/f/c/thumb_273714268.jpeg","member_name":"Natalie Roy"} | 1724949935 | 1524623875430 | {"event_name":"Karate Class - Ken Shin Budo Kai","event_id":"kbsjtmyxgbnc","time":1525129200000,"event_url":"https://www.meetup.com/CWCBarrie/events/250120204/"} | null

不知道我做错了什么，但欢迎任何建议。

Answer 1

你说得对，'GROUP‘是KSQL中的一个关键字。在CREATE STREAM语句中重命名字段名称是行不通的，因为KSQL不知道您的group_info列引用了group字段。

您可以使用列两边的引号来允许您导入主题(目前，引号中的标识符需要大写，但这是一个错误)，例如

CREATE STREAM meetup_rsvp_raw 
(  venue varchar, 
   visibility varchar, 
   response varchar, 
   guests integer, 
   member varchar, 
   rsvp_id bigint, 
   mtime bigint, 
   event varchar, 
   "GROUP" varchar 
) WITH (KAFKA_TOPIC='meetup-rsvp', VALUE_FORMAT='JSON');

请注意，在选择此字段时还需要使用引号：

SELECT `GROUP` from meetup_rsvp_raw limit 5;

我已经创建了一个Github issue to track the lack of documentation in this area。

让我们知道你在这方面的进展。

谢谢,

安迪