learning/prompts/code-explanation/11_io_jdbc.md

Prompt:
What does this code do?
```python
class ExampleRow(NamedTuple):
    id: int
    name: str

class JdbcOptions(PipelineOptions):
    @classmethod
    def _add_argparse_args(cls, parser):
        parser.add_argument(
            '--table_name',
            help='Table name'
        )
        parser.add_argument(
            '--jdbc_url',
            help='JDBC URL'
        )
        parser.add_argument(
            '--driver_class_name',
            help='Driver class name'
        )
        parser.add_argument(
            '--username',
            help='Username'
        )
        parser.add_argument(
            '--password',
            help='Password'
        )

options = JdbcOptions()
coders.registry.register_coder(ExampleRow, coders.RowCoder)

with beam.Pipeline(options=options) as p:

    output = (p | 'Read from JDBC' >> ReadFromJdbc(
        table_name=options.table_name,
        driver_class_name=options.driver_class_name,
        jdbc_url=options.jdbc_url,
        username=options.username,
        password=options.password
        )
        | 'Log Data' >> Map(logging.info))
```

Response:
This code reads data from an [Oracle Java Database Connectivity (JDBC) enabled database](https://docs.oracle.com/javase/8/docs/technotes/guides/jdbc/) using the `ReadFromJdbc` transform from the built-in [JdbcIO connector](https://beam.apache.org/releases/pydoc/current/apache_beam.io.jdbc.html).

```python
class ExampleRow(NamedTuple):
    id: int
    name: str
```

This code defines a named tuple `ExampleRow` with two fields: `id` and `name`.

```python
class JdbcOptions(PipelineOptions):
    @classmethod
    def _add_argparse_args(cls, parser):
        parser.add_argument(
            '--table_name',
            help='Table name'
        )
        parser.add_argument(
            '--jdbc_url',
            help='JDBC URL'
        )
        parser.add_argument(
            '--driver_class_name',
            help='Driver class name'
        )
        parser.add_argument(
            '--username',
            help='Username'
        )
        parser.add_argument(
            '--password',
            help='Password'
        )

options = JdbcOptions()
```

The `JdbcOptions` class defines the command-line arguments `--table_name`, `--jdbc_url`, `--driver_class_name`, `--username`, and `--password`, which specify the JDBC connection parameters. To parse command-line arguments, this code uses [pipeline options](https://beam.apache.org/documentation/patterns/pipeline-options/).

```python
coders.registry.register_coder(ExampleRow, coders.RowCoder)
```

This code registers a coder for the `ExampleRow` class. This is required for the `ReadFromJdbc` transform to read data from the table.

```python
with beam.Pipeline(options=options) as p:

    output = (p | 'Read from JDBC' >> ReadFromJdbc(
        jdbc_url=options.jdbc_url,
        username=options.username,
        password=options.password,
        table_name=options.table_name,
        driver_class_name=options.driver_class_name
        )
        | 'Log Data' >> Map(logging.info))
```

The Apache Beam pipeline uses the `JdbcOptions` class to set the path to the database and the [`ReadFromJdbc` transform](https://beam.apache.org/releases/pydoc/current/apache_beam.io.jdbc.html#apache_beam.io.jdbc.ReadFromJdbc) to read data from the database via JDBC.