Working with TimescaleDB in Continuous Integration: Automating Materialized View Creation

If you’re integrating TimescaleDB into your CI/CD pipeline, you might have encountered a common issue when attempting to create a materialized view directly through your application code. Specifically, the error “ERROR: CREATE MATERIALIZED VIEW … WITH DATA cannot run inside a transaction block” can be a major stumbling block. Let’s explore how you can work around this issue and successfully set up a materialized view directly from your code, bypassing the need for manual terminal operations.

The Root of the Issue

TimescaleDB, an extension of PostgreSQL, does not allow the creation of a materialized view with data during an active transaction block. This is a constraint because PostgreSQL, by default, treats each set of operations executed together as a transaction. When your application sends commands to create a table, a hypertable, and then tries to immediately create a materialized view, it’s all lumped into one transaction block.

A Potential Solution

To automate the creation of materialized views in TimescaleDB within a continuous integration setup, you need to ensure that the command to create the materialized view is executed outside of any transaction. Here’s how you might adjust your existing Python code to handle this.

Adjusting Your Database Connection Code

First, you’ll need to adjust your database connection settings to allow commands to be executed outside of transaction blocks. This can be achieved by setting the autocommit property of your database connection object to True. This property ensures that every command sent to the database is committed immediately without waiting for the explicit commit command.

Here’s how you can modify your connection setup:

pythonCopy codeasync def connect_to_database():
    while True:
        try:
            await asyncio.sleep(1)
            connection = psycopg2.connect(user="postgres", password="password", host="timescaledb", port="5432", database="postgres")
            connection.autocommit = True  # Enable autocommit mode
            cursor = connection.cursor()

            cursor.execute("SELECT EXISTS (SELECT 1 FROM information_schema.tables WHERE table_name = 'bin1s')")
            table_exists = cursor.fetchone()[0]

            if not table_exists:
                cursor.execute(sql_create_table)
                cursor.execute(sql_create_hypertable)
                cursor.execute(sql_create_index)
                cursor.execute(sql_aggregate)  # This is now outside a transaction block
                print("Materialized view 'ohlc_data_minute' created successfully!")
            else:
                print("Table 'bin1s' already exists. Skipping table creation.")

            print("Database setup successful")
            return cursor, connection
        except psycopg2.Error as e:
            print(f"Error connecting to database: {e}")
            print("Retrying in 1 second...")
            await asyncio.sleep(1)

Conclusion

Setting autocommit to True allows each database operation to be committed right away, thereby circumventing the limitations set by PostgreSQL on transaction blocks for operations like creating materialized views. By making this adjustment, your continuous integration pipeline can automate the entire database setup process, including the creation of materialized views, without manual intervention. This approach not only streamlines your development workflow but also ensures that your database schemas and views are consistently set up across different environments.