Mapping array to composite type to a different row type - sql

Question

I want to map an array of key value pairs of GroupCount to a composite type of GroupsResult mapping only specific keys.
I'm using unnest to turn the array into rows, and then use 3 separate select statements to pull out the values.
This feels like a lot of code for something so simple.
Is there an easier / more concise way to do the mapping from the array type to the GroupsResult type?
create type GroupCount AS (
Name text,
Count int
);
create type GroupsResult AS (
Cats int,
Dogs int,
Birds int
);
WITH unnestedTable AS (WITH resultTable AS (SELECT ARRAY [ ('Cats', 5)::GroupCount, ('Dogs', 2)::GroupCount ] resp)
SELECT unnest(resp)::GroupCount t
FROM resultTable)
SELECT (
(SELECT (unnestedTable.t::GroupCount).count FROM unnestedTable WHERE (unnestedTable.t::GroupCount).name = 'Cats'),
(SELECT (unnestedTable.t::GroupCount).count FROM unnestedTable WHERE (unnestedTable.t::GroupCount).name = 'Dogs'),
(SELECT (unnestedTable.t::GroupCount).count FROM unnestedTable WHERE (unnestedTable.t::GroupCount).name = 'Birds')
)::GroupsResult
fiddle
http://sqlfiddle.com/#!17/56aa2/1

Answer 1

A bit simpler. :)
SELECT (min(u.count) FILTER (WHERE name = 'Cats')
, min(u.count) FILTER (WHERE name = 'Dogs')
, min(u.count) FILTER (WHERE name = 'Birds'))::GroupsResult
FROM unnest('{"(Cats,5)","(Dogs,2)"}'::GroupCount[]) u;
db<>fiddle here
See:
Aggregate columns with additional (distinct) filters
Subtle difference: our original raises an exception if one of the names pops up more than once, while this will just return the minimum count. May or may not be what you want - or be irrelevant if duplicates can never occur.
For many different names, crosstab() is typically faster. See:
PostgreSQL Crosstab Query