Aggregate columns containing dictionary in SQL presto - sql

Question

Hi I want to do SQL Presto query for the data table (say user_data) looks like
user | target | result
-----------------------------
1 | b | {A: 1}
2 | a | {C: 2}
1 | c | {A: 2, B: 3}
2 | d | {A: 1}
1 | d | {C: 4}
With this data table, I would like to generate the following two outputs.
Output 1: Aggregate the values of the {key:value} dictionary based on the user and regardless of target
user | result
-------------------
1 | {A:3, B:3, C:4}
2 | {A:1, C:2}
Output 2: Aggregate the last column based on the targets of the user.
user | result
-------------------
1 | {A:[b,c], B:[c], C:[d]}
2 | {A:[d], C:[a]}
Can anyone help me with it? I would really appreciate it.

Answer 1

Second one can be easily achieved with multimap_agg (add transform_values with array_distinct to remove duplicates if needed):
-- sample data
WITH dataset(user, target, result) AS (
values (1, 'b', map(array['A'], array[1])),
(2, 'a', map(array['C'], array[2])),
(1, 'c', map(array['A', 'B'], array[1, 2]))
)
-- query
select user, multimap_agg(k, target)
from dataset,
unnest(result) as t (k,v)
group by user;
Output:
user
_col1
1
{A=[b, c], B=[c]}
2
{C=[a]}
As for the first one - you can look into using map_union_sum if it is available in your version of Presto. Or use some magic with unnest and transform_values:
-- query
select user,
transform_values(
multimap_agg(k, v),
(k,v) -> reduce(v, 0, (s, x) -> s + x, s -> s) -- or array_sum if available
)
from dataset,
unnest(result) as t (k, v)
group by user;
Output:
user
_col1
1
{A=2, B=2}
2
{C=2}