Question

我有一个配置单元表，其中包含复杂类型，即字符串数组。我试图从黑斑羚查询它并将其提取到数组中的列，但当我这样做时，它返回数组的笛卡尔联接结果您可能会看到代码并在您的身边创建示例

-- I adapted from this example https://www.cloudera.com/documentation/enterprise/5-5-x/topics/impala_complex_types.html#complex_types_ex_hive_etl

-- impala side

CREATE TABLE flat_struct_array (continent STRING, country STRING, city STRING);

INSERT INTO flat_struct_array VALUES
    ('North America', 'Canada', 'Toronto') , ('North America', 'Canada', 'Vancouver')
  , ('North America', 'Canada', "St. John\'s") , ('North America', 'Canada', 'Saint John')
  , ('North America', 'Canada', 'Montreal') , ('North America', 'Canada', 'Halifax')
  , ('North America', 'Canada', 'Winnipeg') , ('North America', 'Canada', 'Calgary')
  , ('North America', 'Canada', 'Saskatoon') , ('North America', 'Canada', 'Ottawa')
  , ('North America', 'Canada', 'Yellowknife') , ('Europe', 'France', 'Paris')
  , ('Europe', 'France', 'Nice') , ('Europe', 'France', 'Marseilles')
  , ('Europe', 'France', 'Cannes') , ('Europe', 'Greece', 'Athens')
  , ('Europe', 'Greece', 'Piraeus') , ('Europe', 'Greece', 'Hania')
  , ('Europe', 'Greece', 'Heraklion') , ('Europe', 'Greece', 'Rethymnon')
  , ('Europe', 'Greece', 'Fira');

CREATE TABLE complex_struct_array2
(continent STRING, country array< STRUCT <name: STRING, city: ARRAY <string> >   > ) STORED AS PARQUET;

-- hive side

INSERT INTO complex_struct_array2
select continent, collect_list(struct1)
from (
SELECT continent, named_struct('name', country, 'city', collect_list(city)) as struct1 FROM flat_struct_array GROUP BY continent, country
) a group by continent

select * from complex_struct_array2
-- you'll see table with 2 records, and in Europe it has 2 countries
-- France has 4 cities and Greece has 6 cities

--back to impala side

select * 
from complex_struct_array2 t, t.country t2, t.country.city t3

-- you'll see the result that France contains 10 records (with Greece cities) and vice versa
continent     |name   |item        |
--------------|-------|------------|
Europe        |France |Paris       |
Europe        |France |Nice        |
Europe        |France |Marseilles  |
Europe        |France |Cannes      |
Europe        |France |Athens      |<-- should not be shown
Europe        |France |Piraeus     |<-- should not be shown
Europe        |France |Hania       |<-- should not be shown
Europe        |France |Heraklion   |<-- should not be shown
Europe        |France |Rethymnon   |<-- should not be shown
Europe        |France |Fira        |<-- should not be shown
...

我希望结果是法国仅包含4条记录，并且仅显示我们在Hive方面看到的法国城市

我在Hive上尝试过此方法，它返回了正确的结果

select aa.continent, aa.country_name, cityinfo.*
from (
select a.continent, countryinfo.name as country_name, countryinfo.city  as cityarray
from  complex_struct_array2 a 
lateral view inline(a.country) countryinfo 
) aa
lateral view explode(aa.cityarray) cityinfo

continent     |country_name |col         |
--------------|-------------|------------|
Europe        |France       |Paris       |
Europe        |France       |Nice        |
Europe        |France       |Marseilles  |
Europe        |France       |Cannes      |

在impala中查询结构数组

0 个答案: