如何加入雅典娜的unnest功能？

Question

我在 Athena 上有这个查询

trip.id as tripid
, segment.id as segmentid
, segment.distance as mileage
, segment.maxspeed as maxspeed
, segment.duration as duration
, segment.roadtype as roadtype
, segment.timeslotdata as timeslots
, extract( week from (from_unixtime(trip.referencedate /1000))) as weekyear
, extract( year from (from_unixtime(trip.referencedate /1000))) as year
, extract( month from (from_unixtime(trip.referencedate/1000))) as month
, unn.firstpositionlat
, unn.firstpositionlong
from
trip
, UNNEST(segments) as t(segment)
left join
(
select
position.latitude as firstpositionlat
, position.longitude as firstpositionlong
, position.id as id
from
trip
, UNNEST(segments) as t(segment)
, UNNEST(segment.positions) as t(position)
where
anno = 2021
and mese = 01
and giorno = 01
and tscid = 'XXX'
)
unn
on
segment.startpositionid = unn.id
where
anno = 2021
and mese = 01
and giorno = 01
and tscid = 'XXX'

问题是我无法加入，因为在线 16:19 出现错误，我遇到了这个错误

SYNTAX_ERROR: line 16:19: Column 'segments' cannot be resolved

我想不通问题出在哪里。没有 ON 语句，这个效果很好。

提前致谢

Answer 1

Presto（Athena 的基础 SQL 引擎）仅在 CROSS JOIN 的右侧支持 UNNEST。例如：

-- sample data
WITH dataset (id, animals) AS (
    values (1, ARRAY['dog', 'cat', 'bird']),
    (2, ARRAY['cow', 'pig'])
) 

-- query
SELECT id, animals, a
FROM dataset
CROSS JOIN UNNEST(animals) AS t (a);

输出：

id	animals	a
1	[dog, cat, bird]	dog
1	[dog, cat, bird]	cat
1	[dog, cat, bird]	bird
2	[cow, pig]	cow
2	[cow, pig]	pig

似乎 shorthand 表示法 (from trip, UNNEST(segments) as t(segment)) 在后跟另一个带有 on 条件的连接时无法正常工作，请尝试将其扩展为完整形式：

from trip
cross join UNNEST(segments) as t(segment)
left join (...)
on ...

如何加入雅典娜的unnest功能？

How to join with unnest function in athena?

sql

amazon-s3

amazon-athena

presto

unnest