How to retrieve the list of dynamic nested keys of BigQuery nested records - google-bigquery

Question

My ELT tools imports my data in bigquery and generates/extends automatically the schema for dynamic nested keys (in the schema below, under properties)
It looks like this
How can I get the list of nested keys of a repeated record ? so for example I can group by properties when those items have said property non-null ?
I have tried
select column_name
from my_schema.INFORMATION_SCHEMA.COLUMNS
where
table_name = 'my_table
But it will only list first level keys
From the picture above, I want, as a first step, a SQL query that returns
message
user_id
seeker
liker_id
rateable_id
rateable_type
from_organization
likeable_type
company
existing_attempt
...
My real goal through, is to group/count my data based on a non-null value of a 2nd level nested properties properties.filters.[filter_type]
The schema may evolve when our application adds more filters, so this need to be dynamically generated, I can't just hard-code the list of nested keys.
Note: this is very similar to this question How to extract all the keys in a JSON object with BigQuery but in my case my data is already in a shcema and it's not a JSON object
EDIT:
Suppose I have a list of such records with nested properties, how do I write a SQL query that adds a field "enabled_filters" which aggregates, for each item, the list of properties for wihch said property is not null ?
Example input (properties.x are dynamic and not known by the programmer)
search_id
properties.filters.school
properties.filters.type
1
MIT
master
2
Princetown
null
3
null
master
Example output
search_id
enabled_filters
1
["school", "type"]
2
["school"]
3
["type"]

Answer 1

Have you looked at COLUMN_FIELD_PATHS? It should give you the paths for all columns.
select field_path from my_schema.INFORMATION_SCHEMA.COLUMN_FIELD_PATHS where table_name = '<table>'
[https://cloud.google.com/bigquery/docs/information-schema-column-field-paths]

Answer 2

The field properties is not nested by array only by structures. Then a UDF in JavaScript to parse thise field should work fast enough.
CREATE TEMP FUNCTION jsonObjectKeys(input STRING, shownull BOOL,fullname Bool)
RETURNS Array<String>
LANGUAGE js AS """
function test(input,old){
var out=[]
for(let x in input){
let te=input[x];
out=out.concat(te==null ? (shownull?[x+'==null']:[]) : typeof te=='object' ? test(te,old+x+'.') : [fullname ? old+x : x] );
}
return out;
Object.keys(JSON.parse(input));
}
return test(JSON.parse(input),"");
""";
with tbl as (select struct(1 as alpha,struct(2 as x, 3 as y,[1,2,3] as z ) as B) A from unnest(generate_array(1,10*1))
union all select struct(null,struct(null,1,[999])) )
select *,
TO_JSON_STRING (A ) as string_output,
jsonObjectKeys(TO_JSON_STRING (A),true,false) as output1,
jsonObjectKeys(TO_JSON_STRING (A),false,true) as output2,
concat('["', array_to_string(jsonObjectKeys(TO_JSON_STRING (A),false,true),'","' ) ,'"]') as output_sring,
jsonObjectKeys(TO_JSON_STRING (A.B),false,true) as outpu
from tbl