How can I import a JSON file into PostgreSQL?

Taking it a notch higher :arrow_up:

To be a master at importing JSON files to postgreSQL, I got some extra tricks up my sleeve for you:

Struggling with nested JSON objects?

Create a staging table to unpack the nested JSON goodies:

-- "Nested JSONs are like those Russian dolls, let's open one up!"
CREATE TABLE staging_table (
  id serial PRIMARY KEY,
  raw_data jsonb
);

-- "Moving raw data, like moving houses...hard but fun"
COPY staging_table(raw_data) FROM '/path/to/jsonfile.json';

-- "Remember you are a data ninja, slicing and dicing data"
INSERT INTO target_table (column1, column2)
SELECT raw_data->>'key1', raw_data->'nested'->>'key2'
FROM staging_table;


Easier engagement with JSON data

You can use json_populate_recordset to make JSON data look like good old relational data:

-- "Creating a table is like choosing the right-sized Tupperware for your data"
CREATE TABLE json_records AS
SELECT * FROM json_populate_recordset(null::your_table_type, (SELECT raw_data FROM staging_table));


Here's how to upsert data

In case your JSON contains data for existing records, slap in the ON CONFLICT clause to handle it all:

-- "Did someone say UPSERT? You're covered mate!"
INSERT INTO target_table (id, data)
SELECT * FROM json_populate_recordset(null::target_table, '{"id": 1, "data": "new"}')
ON CONFLICT (id) DO UPDATE SET
data = EXCLUDED.data;


Taking your game to the SQL stratosphere

Elevate your JSON import game with a common table expression (CTE):

-- "With great CTE, comes great convenience!"
WITH preprocessed_json AS (
  SELECT id, data
  FROM json_populate_recordset(null::target_table, (SELECT raw_data FROM staging_table))
)
INSERT INTO target_table (id, data)
SELECT id, data FROM preprocessed_json
ON CONFLICT (id) DO NOTHING;


Boost your query speed with JSONB

The jsonb data type stores data in a decomposed binary format. It's like having a power engine for your queries!

-- "JSONB is basically JSON on steroids"
ALTER TABLE target_table ALTER COLUMN data TYPE jsonb USING data::jsonb;


Advanced tricks and tips

Harnessing meta-commands

Who's meta? Well, with psql, PostgreSQL's command-line interface, you can use \set and \copy to load files and execute SQL scripts:

-- "Meta is your new friend"
\set content `cat /path/to/jsonfile.json`
INSERT INTO json_data_table (data) VALUES (:'content');


Dealing with big files

When your JSON file is so large it breaks the scale, the csv trick will save the day:

-- "How to feed a big JSON file to PostgreSQL? Just use CSV!"
\copy large_json_data_table (data) FROM '/path/to/large_jsonfile.json' (FORMAT csv);


Turbocharge your JSON manipulation

jq and spyql can turn JSON data into SQL-compatible insert statements, faster than a twitchy rabbit:

-- "Making JSON and SQL play well together"
cat /path/to/jsonfile.json | jq '...' | spyql '...' | psql -c "COPY (FIELD LIST) FROM STDIN";
