Hi,
We started to work with Avro in CDH4 and to query the Avro files using
Hive.
This does work fine for us, except for unions.
We do not understand how to query the data inside a union using Hive.
For example, let's look at the following schema:
{
"type":"record",
"name":"event",
"namespace":"com.mysite",
"fields":[
{
"name":"eventbody",
"type":{
"type":"record", "name":"eventbody",
"fields":[
{
"name":"body",
"type":[
"null",
{
"type":"record",
"name":"event1",
"fields":[
{
"name":"event1Header",
"type":["null", { "type":"array",
"items":"string" }], "default":null
},
{
"name":"event1Body",
"type":["null", { "type":"array",
"items":"string" }], "default":null
}
]
},
{
"type":"record",
"name":"event2",
"fields":[
{
"name":"page",
"type":{
"type":"record", "name":"URL",
"fields":[{ "name":"url", "type":"string" }]
},
"default":null
},
{
"name":"referrer", "type":"string",
"default":null
}
]
}
],
"default":null
}
]
},
"default":null
}
]}
Note that "body" is a union of three types:
null, "event1" and "event2"
If I run such a query:
SELECT eventbody.body from SRC;
I get line like this:
{2:{"page":{"url":"http://www.musite.com/index.jsp"},"referrer":{"url":";
www.search.com"}}}
The number "2" in the beginning of the JSON structure represents "events2"
union because it is the third element in the union.
My question then: If I want to query fields inside event2. E.g., the
page.url or the referrer fields how do I construct the select statement?
Thank you,
Ran
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