postgres columns attribute for json - json

Question

I am currently a happy user of ngx_postgres. However I recently discover I need to do something very weird. Basically I need to produce the following json output:
{
"PatientName": {
"Tag": "00100010",
"VR": "PN",
"PersonName": [
{
"SingleByte": "Wang^XiaoDong",
"Ideographic": "王^小東"
}
]
},
},
{
"PatientName": {
"Tag": "00100010",
"VR": "PN",
"PersonName": [
{
"SingleByte": "John^Doe",
}
]
},
}
With a little reading of the DICOM standard it is easy to create (simplified) a table of equivalent for Keyword, Tag and VR:
CREATE TABLE equiv (
"Keyword" varchar(64) PRIMARY KEY,
"Tag" char(8) NOT NULL,
"VR" char(2) NOT NULL,
);
Well now the tricky part is this indirection with PatientName that I do not understand, I tried:
CREATE TABLE patientname (
"SingleByte" varchar(64) primary key,
"Ideographic" varchar(64),
);
CREATE TABLE patientlevel_impl_detail (
"PatientName" varchar(64) references patientname("SingleByte"),
"PatientID" character varying(64) NOT NULL
);
CREATE view patientlist as select
patientname."SingleByte",
patientname."Ideographic",
patientname."Phonetic",
patientlevel_impl_detail."PatientID"
FROM patientlevel_impl_detail,patientname where patientlevel_impl_detail."PatientName" = patientname."SingleByte";
However in any case a TABLE and/or a VIEW is always flatten, and instead I am getting something like:
$ curl http://localhost:8080/patients
[
{
"Tag": "00100010",
"VR": "PN",
"SingleByte": "John^Doe",
"Ideographic": null,
},
]
So I do not see how I can make PersonName an array of nested string (nested json tree).
Note: I am not using 9.3, I need to use 9.1 for now

Answer 1

On 9.1, do yourself a favor and get the json extension for 9.1. It will save you a lot of work.
The second thing you need to do is to create a nested data structure as a view which matches your json structure. You will use array_agg() for this:
CREATE view patientlist as select
arrayagg(patientname) as "PatientName"
patientlevel_impl_detail."PatientID"
FROM patientlevel_impl_detail,patientname
where patientlevel_impl_detail."PatientName" = patientname."SingleByte";
Then you should be able to:
SELECT row_to_json(patientlist) FROM patientlist;