MSQ exporting fails to output headers with complex column types (array/json)

[egor-ryashin]

MSQ exporting fails to output headers with complex column types (array/json)

Affected Version

29.0.0

Description

This query produces a file with incorrect headers and complex object aren't properly converted to strings:

INSERT INTO
  EXTERN(
    local(exportPath => '/tmp/test_export11')
  )
AS csv
SELECT
  1 m1, 'a' d1, array[1,2] array1, json_object('a':1) json1

CSV contents:

v0,v1,v2,v3
1,a,[Ljava.lang.Number;@9553825,StructuredData{value={a=1}}

Expected something like:

m1,d1,array1,json1
1,a,"[1,2]","{""a"":1}"

[LakshSingla]

29.0.1 and subsequent versions should resolve this via #16167.