migra

import os from migra import Migration from sqlalchemy import create_engine, MetaData, Table, Column, Integer, String # Use environment variables for PostgreSQL connection strings for safety # Ensure POSTGRES_SOURCE_URL and POSTGRES_TARGET_URL are set to real PostgreSQL databases. # For a demo, you can point them to two different databases on the same host, # or create a temporary 'source' schema and an empty 'target' schema. source_url = os.environ.get('POSTGRES_SOURCE_URL', 'postgresql+psycopg2://user:pass@localhost:5432/source_db') target_url = os.environ.get('POSTGRES_TARGET_URL', 'postgresql+psycopg2://user:pass@localhost:5432/target_db') # Establish SQLAlchemy engines source_engine = create_engine(source_url) target_engine = create_engine(target_url) # Define a simple schema for the "source" database (what we want the target to look like) source_metadata = MetaData() Table('users', source_metadata, Column('id', Integer, primary_key=True), Column('name', String(50), nullable=False), Column('email', String(100), unique=True)) # Apply the source schema to the source database (if not already there) print("Ensuring source schema exists in source_db...") with source_engine.connect() as conn: source_metadata.create_all(conn) conn.commit() # The target database is assumed to be empty or have an older schema. # migra will generate SQL to make target look like source. # Create a Migration object to compare the live schemas m = Migration(source=source_engine, target=target_engine) # Get the DDL statements to transform target to source sql_statements = m.statements print("\nGenerated SQL statements to migrate target_db to source_db schema:") if sql_statements: for stmt in sql_statements: print(stmt) # To apply the migration to the target database (UNCOMMENT WITH EXTREME CAUTION!) # print("\nApplying migration to target database...") # with target_engine.connect() as conn: # m.apply(conn) # conn.commit() # print("Migration applied successfully.") else: print("No migration statements needed (schemas are identical or target is already ahead).")