Execute .sql schema in psycopg2 in Python

Question

I have a PostgreSQL schema stored in .sql file. It looks something like:

CREATE TABLE IF NOT EXISTS users (
    id INTEGER PRIMARY KEY,
    facebook_id TEXT NOT NULL,
    name TEXT NOT NULL,
    access_token TEXT,
    created INTEGER NOT NULL
);

How shall I run this schema after connecting to the database?

My existing Python code works for SQLite databases:

# Create database connection
self.connection = sqlite3.connect("example.db")

# Run database schema
with self.connection as cursor:
    cursor.executescript(open("schema.sql", "r").read())

But the psycopg2 doesn’t have an executescript method on the cursor. So, how can I achieve this?

Asked By: linkyndy

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Source

Answer 1

You can just use execute:

with self.connection as cursor:
    cursor.execute(open("schema.sql", "r").read())

though you may want to set psycopg2 to autocommit mode first so you can use the script’s own transaction management.

It’d be nice if psycopg2 offered a smarter mode where it read the file in a statement-at-a-time and sent it to the DB, but at present there’s no such mode as far as I know. It’d need a fairly solid parser to do it correctly when faced with $$ quoting (and its $delimiter$ variant where the deimiter may be any identifier), standard_conforming_strings, E'' strings, nested function bodies, etc.

Note that this will not work with:

anything containing psql backslash commands
COPY .. FROM STDIN
very long input

… and therefore won’t work with dumps from pg_dump

Answered By: Craig Ringer

Answer 2

I can’t reply to comments of the selected answer by lack of reputation, so i’ll make an answer to help with the COPY issue.

Depending on the volume of your DB,pg_dump --inserts outputs INSERTs instead of COPYs

Answered By: Lisael

Execute .sql schema in psycopg2 in Python

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