Question

我创建了一个表格如下：

CREATE TABLE TEST (ID INT, SCORE INT, NAME STRING);

并插入了几条记录。我想执行top-k查询，返回每个ID的最高记录，按SCORE排序。

我正在使用Hivemall库中的each_top_k（）UDF，如下所示：https://hivemall.incubator.apache.org/userguide/misc/topk.html

SELECT EACH_TOP_K(1, ID, SCORE, ID, NAME) AS (RANK, SCORE, ID, NAME) FROM (
SELECT * FROM TEST
CLUSTER BY ID
) T;

成功返回每个ID的顶级SCORE。但是，我创建了一个视图，如下所示：

CREATE VIEW TEST_VIEW AS SELECT EACH_TOP_K(1, ID, SCORE, ID, NAME) AS (RANK, SCORE, ID, NAME) FROM (
SELECT * FROM TEST
CLUSTER BY ID
) T;

并且它成功执行。但是，那么简单

SELECT * FROM TEST_VIEW;

返回以下错误：

错误：编译语句时出错：FAILED：SemanticException View test_view对应于UDTF，而不是SelectOperator。（状态= 42000，代码= 40000）

我无法提及此错误。有什么建议吗？

Answer 1

我认为Hive在运行时为你的udtf推断每个字段的数据类型有问题。这应该解决它，尝试在查询之上提出查询，例如

CREATE VIEW TEST_VIEW AS 
select cast(rank as long) as rank, cast(score as double) as score, cast(id as string) as id, cast(name as string) as name from (
SELECT EACH_TOP_K(1, ID, SCORE, ID, NAME) AS (RANK, SCORE, ID, NAME) FROM (
SELECT * FROM TEST
CLUSTER BY ID
) T ) t2;

无法查询依赖于UDTF的Hive视图

1 个答案: