Is it possible to add index values to the rows of a postgreSQL query when expanding JSON array with json_array_elements?

Question

I have a database of resume data in json format which I am trying to transform. One of the sections in each jsib is work_history, this is in the form of a json array i.e.

"work_experience":[
   {
      "job_title":"title",
      "job_description":"description"
   },
   {
      "job_title":"title",
      "job_description":"description"
   }
]

I am iterating over each resume (json file) and importing this data into a new table using dbt and postgreSQL with each element of the array being a new row with the associated metadata of the resume. Here is the code I used for this

select
    json_array_elements(rjt.raw_json::json -> 'data' -> 'work_experience')  as we,
    json_array_elements(rjt.raw_json::json -> 'data' -> 'work_experience') -> 'job_title' as "name",
    rjt.uuid as uuid
from raw_json_table rjt

The last thing that I need to do is add a column that lists the index that each job came from within its individual workexperience array i.e. if a job was the third element in the array it would have a 2 in the "source_location" column. How can I generate this index such that it starts at 0 for each new json file.

raw_json should be defined as jsonb or at least json, not as text — user330315
– user330315, Commented May 25, 2022 at 6:04

user330315 · Accepted Answer · 2022-05-25 06:00:26Z

3

Move the function to the FROM clause (where set-returning functions should be used). Then you can use with ordinality which also returns a column that indicates the index inside the array

select w.experience as we,
       w.experience ->> 'job_title' as "name",
       w.experience ->> 'job_description' as "description",
       w.idx as "index",
       rjt.uuid as uuid
from raw_json_table rjt
  left join json_array_elements(rjt.raw_json::json -> 'data' -> 'work_experience') with ordinality 
            as w(experience, idx) on true

The left join is necessary so that rows from raw_json_table that don't contain array elements are still included.

answered May 25, 2022 at 6:00

user330315

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