[英]HiveQL query returns no results and no errors
我在Ubuntu 14.0上运行Apache Hadoop 2.6.0,并且在Hive 0.13.0中创建了一个表,如下所示:
CREATE TABLE IF NOT EXISTS recipes_hive.cuisine (
ID INT COMMENT 'Cuisine ID.',
name STRING COMMENT 'Cusine name - primary key.',
area STRING COMMENT 'Name of the area of origin - foreign key.',
scope STRING COMMENT 'Either country or area.')
COMMENT 'Table containing cuisines data.'
ROW FORMAT DELIMITED FIELDS TERMINATED BY ','
STORED AS TEXTFILE;
我用语句填充数据:
LOAD DATA LOCAL INPATH 'path_to_file/CUISINE.csv'
OVERWRITE INTO TABLE recipes_hive.cuisine;
我的数据库中有几个这样的表,它们都是用相同的过程创建并填充的。 在运行简单查询时,例如:
SELECT * FROM cuisine
甚至在WHERE子句中具有某些条件的情况下,我都能获得预期的结果,但运行更复杂的查询时会蹲下。 例如:
SELECT cuisine.name, SUM(IF (ingredient.category = "fruit",1,2))/count(*) AS PERC
FROM cuisine JOIN recipe ON recipe.cuisine = cuisine.name JOIN part_of ON part_of.id_recipe = recipe.id JOIN ingredient ON ingredient.name = part_of.ingredient
GROUP BY cuisine.name
ORDER BY PERC DESC
, 要么:
SELECT ingredient.id, ingredient.name
FROM cuisine JOIN recipe ON recipe.cuisine = cuisine.name JOIN part_of ON part_of.id_recipe = recipe.id JOIN ingredient ON ingredient.name = part_of.ingredient
WHERE ingredient.id IN (
SELECT ingredient.id
FROM cuisine c JOIN recipe ON recipe.cuisine = c.name JOIN part_of ON part_of.id_recipe = recipe.id JOIN ingredient ON ingredient.name = part_of.ingredient
WHERE c.name = "Pakistan") AND cuisine.name = "Bangladesh"
第一个示例计算一些百分比,第二个示例检查互斥元素。
正确调用了MapReduce和Hadoop,它们没有返回错误。 输出以以下结尾:
Execution completed successfully
MapredLocal task succeeded
OK
Time taken: 122.119 seconds
我已经检查了网络,人们也遇到了类似的问题。 我检查了:
但未能解决我的问题。 数据实际上位于HDFS中,并且如前所述,它可用于简单查询。
因此,我的Hive实例有问题或我的查询未正确编写。
任何帮助将不胜感激。 最好的祝福。
您确定结果联接将为非空。 因为,您已经实现了内部联接,所以即使一个表缺少记录,整个结果集也为0。尝试添加带有“ IS NULL”的左联接以验证所有表是否对结果集有所帮助。 如果所有子表在联接后各自的列中都具有非null值,则查询是好的。
如果我们有包含ID = {1,2,3}的Cuisine表和包含ID = {5,6,7}的Recipe表,那么即使这些表是非空的,当我们进行INNER JOIN时,我们仍然不会返回任何行Cuisine.ID = Recipe.ID(因为2个表中的ID不同),请检查是否没有这种条件。
SELECT count(1)
FROM cuisine c JOIN recipe ON recipe.cuisine = c.name WHERE c.name = "Pakistan";
--- must return > 0
select count(1) from recipe as recipe
JOIN part_of ON part_of.id_recipe = recipe.id ;
--- must return > 0
select count(1) from part_of as part_of
JOIN ingredient ON ingredient.name = part_of.ingredient ;
--- must return > 0
因此,当所有count(*)非零时,内部查询将返回一行。 现在测试外部选择:
SELECT ingredient.id, ingredient.name
FROM cuisine JOIN recipe ON recipe.cuisine = cuisine.name JOIN part_of ON part_of.id_recipe = recipe.id JOIN ingredient ON ingredient.name = part_of.ingredient
WHERE ingredient.id = <inner query result> and cuisine.name = "Bangladesh";
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