Postgresql json select from values in second layer of containment of arrays - postgresql

Question

I have a jsonb column 'data' that contains a tree like json, example:
{
"libraries":[
{
"books":[
{
"name":"mybook",
"type":"fiction"
},
{
"name":"yourbook",
"type":"comedy"
}
{
"name":"hisbook",
"type":"fiction"
}
]
}
]
}
I want to be able to do a index using query that selects a value from the indented "book" jsons according to the type.
so all book names that are fiction.
I was able to do this using jsonb_array_elements a join query, but as i understand this would not be optimized with using the GIN index.
my query is
select books->'name'
from data,
jsonb_array_elements(data->'libraries') libraries,
jsonb_array_elements(libraries->'books') books,
where books->>'type'='grading'

Answer 1

If the example data you are showing is the type of data that is common in your JSON, I would suggest that you may be setting things up wrong.
Why not make a library table and a book table and not use JSON at all, it seems JSON is not the right choice here.
CREATE TABLE library
(
id serial,
name text
);
CREATE TABLE book
(
isbn BIGINT,
name text,
book_type text
);
CREATE TABLE library_books
(
library_id integer,
isbn BIGINT
)
select book.* from library_books where library_id = 1;