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The Art of PostgreSQL

Schemaless Design in PostgreSQL

Learn about schemaless design and how PostgreSQL manages giant documents.

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An area where the NoSQL systems have been prominent is in breaking with the normalization rules and the hard step of modeling a database schema. Instead, most NoSQL systems will happily manage any data the application sends through. This is called the schemaless approach.

In truth, there’s no such thing as a schemaless design, actually. What it means is that the name and type of the document properties, or fields, are hard-coded into the application code.

JSON data set

A readily available JSON dataset is provided at MTGJSON that provides Magic: The GatheringTM card data in JSON format, using the CC0 license. We can load it easily given this table definition:

PostgreSQL
begin;
drop schema if exists magic cascade;
create schema magic;
create table magic.allsets(data jsonb);
commit;

Then we use a small Python script:

Python
#! /usr/bin/env python3
import psycopg2
PGCONNSTRING = "user=postgres dbname=magic"
if __name__ == '__main__':
    pgconn = psycopg2.connect(PGCONNSTRING)
    curs = pgconn.cursor()
    allset = open('MagicAllSets.json').read()
    allset = allset.replace("'", "''")
    sql = "insert into magic.allsets(data) values('%s')" % allset
    curs.execute(sql)
    pgconn.commit()
    pgconn.close()

Giant documents and PostgreSQL

The giant JSON document in a single table doesn’t represent the kind of schemaless design. It goes ...