PostgreSQL regexp_replace square brackets to other format - sql

Question

I have this column text in a table which contains following string
{
"person": {
"id": "b01d9bf1-998f-4fa8-879a-0f8d0de4b626",
"creationDate": [
2022,
1,
22
],
"modificationDate": [
2022,
1,
27
]
}
}
I have the following regexp_matches query:
select regexp_matches('"creationDate": [2022,1,22], "modificationDate": [2022,1,27],', '\[(.[^)]+)\]', 'g')
but I need to replace
"creationDate": [2022,1,22], "modificationDate": [2022,1,27],
to
"creationDate": "2022-01-22", "modificationDate": "2022-01-27",
I'm not very good working with regular expressions. Also the difficulty is in adding a leading zero to the month as you can see.

Answer 1

Regex-based
A nested regex replacement does the trick:
select regexp_replace(
regexp_replace(
'"creationDate": [2022,1,22], "modificationDate": [2022,1,27],'
, '\[(\d+),(\d+),(\d+)\]'
, '"\1-\2-\3"'
, 'g'
)
, '-(\d)-'
, '-0\1-'
, 'g');
The outer replacement only fires if the month is represented by a single digit.
JSON-based
Dwelling on the comment by #a_horse_with_no_name, the following query operates uses json operators:
select x.key
, (x.value ->> 0) || '-' || LPAD(x.value ->> 1, 2, '0') || '-' || LPAD(x.value ->> 2, 2, '0') mydate
from json_each ( '{"creationDate": [2022,1,22], "modificationDate": [2022,1,27] }'::json ) x
;
The query builds a set of records from a JSON object consisting of a key (the JSON property name) and a value of the native JSON datatype, which happens to be an array. The array elements are extracted, padded with leading zeros where appropriate and concatenated.
See the Postgresql docs for JSON operators and functions for more info.
Full-fledged example
Query to produce a recordset of persons containing their id plus the creation and modification date based on a json array of objects as given in the question.
select id
, ("creationDate" ->> 0) || '-' || LPAD("creationDate" ->> 1, 2, '0') || '-' || LPAD("creationDate" ->> 2, 2, '0') creation_date
, ("modificationDate" ->> 0) || '-' || LPAD("modificationDate" ->> 1, 2, '0') || '-' || LPAD("modificationDate" ->> 2, 2, '0') modification_date
from jsonb_to_recordset (
(
select jsonb_path_query_array ( orig.j, '$.person' ) part
from (
select '[
{ "person": { "id": "b01d9bf1-998f-4fa8-879a-0f8d0de4b626", "creationDate": [2022,1,22], "modificationDate": [2022,1,27] } }
, { "person": { "id": "deadcafe-998f-4fa8-879a-0f8d0de4b626", "creationDate": [2000,1,1], "modificationDate": [2000,12,31] } }
]'::jsonb j
) orig
)
) as x( id varchar(50), "creationDate" json, "modificationDate" json )
;
Available live here (dbfiddle.co.uk).