> ## Documentation Index
> Fetch the complete documentation index at: https://docs.turntable.so/llms.txt
> Use this file to discover all available pages before exploring further.

# Sources

> Sources are typed data schemas that help Vinyl understand what data is available

## Setting up a Resource

A resource serves as a connection to data sources. Resources can be a data warehouse (BigQuery, Snowflake), transactional databases (Postgres), object storage (S3), data lakes (Delta) or local files (parquet, csv, json).
Vinyl comes with standard resource connectors:

* TableFileConnector (csv, json, parquet)
* BigQueryConnector
* PostgresConnector
* DatabaseFileConnector (duckdb)

Resources are defined in the `resources.py` file of our project. Resources are used to fetch metadata and source data queries.
Here's an example of a postgres connection:

```python my_project/resources.py theme={null}
from vinyl import resource
from vinyl.connectors import PostgresConnector

@resource
def saas_product_data():
    return PostgresConnector(
        host="db.mypostgres.com",
        port="5432",
        user="postgres",
        password="password",
        tables=["postgres.*.*"],
    )
```

## Generate Sources

Once we've defined a resource, we can pull in source data schemas automatically using the following vinyl CLI command

```bash theme={null}
vinyl generate sources
```

This command populates the `sources/` directory with typed source data schemas. These schemas are used to understand the structure of the data and to generate source data queries.
Here's an example of a source schema for a postgres table:

```python my_project/sources/user.py theme={null}
class User:
    user_id: t.String(nullable=False)
    created_at: t.Timestamp(timezone=None, scale=None, nullable=True)
    email: t.String(nullable=True)
    karma: t.Int32(nullable=True)
    last_login: t.Timestamp(timezone=None, scale=None, nullable=True)
    payment_method_id: t.String(nullable=True)
```

## Using Sources

Sources are used just like any python class. You can import a source in a notebook, script or vinyl project:

```python my_project/myfile.py theme={null}
from my_project.sources import User

user_table = User()
print(user_table.schema)
```

Generated sources serve as a data contract. With sources, you can validate data transforms without hitting the database and detect upstream schema drift to prevent breaking changes.

## List Sources

As you're adding resources and generating sources, you can list all the sources in your project using the following vinyl CLI command:

```bash theme={null}
vinyl sources list
```