[CALCITE-4063] Unnest an array of single-item structs causes ClassCastException

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.23.0
• Fix Version/s: 1.24.0
• Component/s: core
• Labels: pull-request-available
• Assignee: Ruben Q L
• Reporter: Ruben Q L
• Created: 12/Jun/20 14:15
• Updated: 19/Feb/21 15:53
• Resolved: 20/Jun/20 17:31

Description

If we run the following queries with UNNEST operator, we get the expected results:

select * from UNNEST(array[3, 4]) as T2(y);
-- y=3
-- y=4

select * from UNNEST(array[array[3], array[4]]) as T2(y)
-- y=[3]
-- y=[4]

select * from UNNEST(array[ROW(3), ROW(4)]) as T2(y)
-- y=[3]
-- y=[4]
-- Is this result ok? (see first comment of the current ticket)

However, if we try to combine them with a correlation with some other values, as we could do in more realistic examples:
select * from dept_nested as d, UNNEST(d.employees) e2

The first two return the expected results, but the last one throws an exception:

select * from (values (1), (2)) T1(x), UNNEST(array[3, 4]) as T2(y);
-- x=1; y=3
-- x=1; y=4
-- x=2; y=3
-- x=2; y=4

select * from (values (1), (2)) T1(x), UNNEST(array[array[3], array[4]]) as T2(y);
-- x=1; y=[3]
-- x=1; y=[4]
-- x=2; y=[3]
-- x=2; y=[4]

select * from (values (1), (2)) T1(x), UNNEST(array[ROW(3), ROW(4)]) as T2(y);
-- ERROR!!!
-- java.lang.ClassCastException: org.apache.calcite.runtime.FlatLists$Flat1List cannot be cast to java.lang.Integer

Issue Links

• relates to: CALCITE-2000 UNNEST a collection that has a field with nested data generates an Exception
• relates to: CALCITE-4064 Unnest on array with nested structs causes ArrayStoreException
• links to: PR#2031