RedShift: Unnest subquery's result on leader is not supported - amazon-redshift

Question

I try to parse JSON in RedShift.
My string in column "inputs" is:
[{"desc": "How many people does the video contain?", "name": "Number of People", "type": "dropdown", "values": ["", "Only 1", "2-3", "3+"]}, {"desc": "What is the camera position?", "name": "Movement", "type": "dropdown", "values": ["", "Fixed position", "Moving"]}, {"desc": "From which angle did you shoot the video?", "name": "Shoot Angle", "type": "dropdown", "values": ["", "Frontal recording", "Tight angle: 10-40 degree", "Wide angle: 40-70 degree"]}, {"desc": "From which distance did you shoot the video?", "name": "Distance", "type": "dropdown", "values": ["", "Near/Selfie", "Mid (3-6 ft)", "Far (>6 ft)"]}, {"desc": "What is the video lighting direction?", "name": "Lighting Direction", "type": "dropdown", "values": ["", "Front lit", "Side lit", "Back lit"]}, {"desc": "What is the video background?", "name": "Background", "type": "dropdown", "values": ["", "Outdoors", "In office", "At home", "Plain background"]}, {"desc": "What is the topic in your speech?", "name": "Topic", "type": "dropdown", "values": ["", "Arts and Media", "Business", "Education", "Entertainment", "Food/Eating", "Nutrition", "Healthcare ", "High School Life", "Mental Health", "News", "Technology", "Morals and Ethics", "Phones and Apps", "Sports", "Science"]}]
My task is: "Each value, name, desc from JSON need to be stored as one row in the table".
Example:
id: 1, desc: "How many people does the video contain?"
id: 2, desc: "What is the camera position?"
etc.
I use query:
SELECT c.*, d.desc, d.name, d.values FROM source.table AS c, c.inputs AS d;
And got an ERROR: navigation on column "inputs" is not allowed as it is not SUPER type
And query:
SELECT c.*, d.desc, d.name, d.values FROM source.table AS c, JSON_PARSE(c.inputs) AS d;
gives me another error: "function expression in FROM may not refer to other relations of same query level"
But when I have created test JSON as:
CREATE TABLE test_parse_json_super
(
id smallint,
details super
);
INSERT INTO test_parse_json_super VALUES(1, JSON_PARSE('[{"desc": "How many people does the video contain?", "name": "Number of People", "type": "dropdown", "values": ["", "Only 1", "2-3", "3+"]}, {"desc": "What is the camera position?", "name": "Movement", "type": "dropdown", "values": ["", "Fixed position", "Moving"]}, {"desc": "From which angle did you shoot the video?", "name": "Shoot Angle", "type": "dropdown", "values": ["", "Frontal recording", "Tight angle: 10-40 degree", "Wide angle: 40-70 degree"]}, {"desc": "From which distance did you shoot the video?", "name": "Distance", "type": "dropdown", "values": ["", "Near/Selfie", "Mid (3-6 ft)", "Far (>6 ft)"]}, {"desc": "What is the video lighting direction?", "name": "Lighting Direction", "type": "dropdown", "values": ["", "Front lit", "Side lit", "Back lit"]}, {"desc": "What is the video background?", "name": "Background", "type": "dropdown", "values": ["", "Outdoors", "In office", "At home", "Plain background"]}, {"desc": "What is the topic in your speech?", "name": "Topic", "type": "dropdown", "values": ["", "Arts and Media", "Business", "Education", "Entertainment", "Food/Eating", "Nutrition", "Healthcare ", "High School Life", "Mental Health", "News", "Technology", "Morals and Ethics", "Phones and Apps", "Sports", "Science"]}]'));
and use query "SELECT c.*, d.desc, d.name, d.values FROM test_parse_json_super AS c, c.details AS d;" from official RedShift docs - it's work fine and all data from JSON is parsing to each rows and JSON is correct.
How I can fix query for work with my real data?
Thnx.

Answer 1

It looks like you are confusing the concepts of SUPER data type for sub-select. You cannot cast a string to super (using JSON_PARSE) and then use it as the source of the FROM clause at the same level of the query. I don't have a complete understanding of your situation but I think something like this should get you closer:
SELECT c.*, d.desc, d.name, d.values
FROM (
SELECT *, JSON_PARSE(inputs) AS inputs_super
FROM source.table
) AS c,
JSON_PARSE(c.inputs_super) AS d
;
(This is an off the cuff response to show structure so please forgive any syntax issues)

Answer 2

It will be more correct:
SELECT c.*, d.desc, d.name, d.values
FROM (
SELECT id, created, JSON_PARSE(inputs) AS inputs_super
FROM source.table
WHERE prompttype = 'input'
) AS c,
c.inputs_super AS d
;

Answer 3

I ran into a similar issue. The json has to be parsed in a created table before use, and cannot be referenced via a CTE or subquery and then used. Therefore I believe the answer is:
CREATE TABLE my_table_with_super
AS
(
SELECT c.*,
JSON_PARSE(c.inputs) AS inputs_json_super
FROM source.table c
);
SELECT c.*,
json_row.desc,
json_row.name,
json_row.values
FROM my_table_with_super as c,
c.inputs_json_super as json_row;