> ## Documentation Index
> Fetch the complete documentation index at: https://mage-staging.mintlify.site/llms.txt
> Use this file to discover all available pages before exploring further.

# PostgreSQL

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  <img alt="" src="https://user-images.githubusercontent.com/78053898/198754399-3b594af0-cf84-41d3-8faf-e1f6e4c5182d.png" />
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## Add credentials

1. Create a new pipeline or open an existing pipeline.
2. Expand the left side of your screen to view the file browser.
3. Scroll down and click on a file named `io_config.yaml`.
4. Enter the following keys and values under the key named `default` (you can
   have multiple profiles, add it under whichever is relevant to you)

```yaml theme={null}
version: 0.1.1
default:
  POSTGRES_DBNAME: ...
  POSTGRES_HOST: ...
  POSTGRES_PASSWORD: ...
  POSTGRES_PORT: ...
  POSTGRES_USER: ...
  POSTGRES_CONNECTION_METHOD: direct
  POSTGRES_SSH_HOST:
  POSTGRES_SSH_PORT: 22
  POSTGRES_SSH_USERNAME:
  POSTGRES_SSH_PASSWORD:
  POSTGRES_SSH_PKEY:
```

### SSH tunneling

If you want to connect to Postgres cluster with ssh tunnel, update the value of `POSTGRES_CONNECTION_METHOD` to `ssh_tunnel`, and enter the values for keys with prefix `POSTGRES_SSH`.

| Key                     | Description                                                                                                                                                  | Sample value           |
| ----------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------ | ---------------------- |
| `POSTGRES_SSH_HOST`     | The host of the intermediate bastion server.                                                                                                                 | `123.45.67.89`         |
| `POSTGRES_SSH_PORT`     | The port of the intermediate bastion server. Default value: 22                                                                                               | `22`                   |
| `POSTGRES_SSH_USERNAME` | The username used to connect to the bastion server.                                                                                                          | `username`             |
| `POSTGRES_SSH_PASSWORD` | (Optional) The password used to connect to the bastion server. It should be set if you authenticate with the bastion server with password.                   | `password`             |
| `POSTGRES_SSH_PKEY`     | (Optional) The path to the private key used to connect to the bastion server. It should be set if you authenticate with the bastion server with private key. | `/path/to/private/key` |

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## Using SQL block

1. Create a new pipeline or open an existing pipeline.
2. Add a data loader, transformer, or data exporter block.
3. Select `SQL`.
4. Under the `Data provider` dropdown, select `PostgreSQL`.
5. Under the `Profile` dropdown, select `default` (or the profile you added
   credentials underneath).
6. Next to the `Save to schema` label, enter the schema name you want this block
   to save data to.
7. Under the `Write policy` dropdown, select `Replace` or `Append` (please see
   [SQL blocks guide](/guides/blocks/sql-blocks) for more
   information on write policies).
8. Enter in this test query: `SELECT 1`.
9. Run the block.

<br />

## Using Python block

1. Create a new pipeline or open an existing pipeline.
2. Add a data loader, transformer, or data exporter block (the code snippet
   below is for a data loader).
3. Select `Generic (no template)`.
4. Enter this code snippet (note: change the `config_profile` from `default` if
   you have a different profile):

```python theme={null}
from mage_ai.settings.repo import get_repo_path
from mage_ai.io.config import ConfigFileLoader
from mage_ai.io.postgres import Postgres
from os import path
from pandas import DataFrame

if 'data_loader' not in globals():
    from mage_ai.data_preparation.decorators import data_loader


@data_loader
def load_data_from_postgres(**kwargs) -> DataFrame:
    query = 'SELECT 1'
    config_path = path.join(get_repo_path(), 'io_config.yaml')
    config_profile = 'default'

    with Postgres.with_config(ConfigFileLoader(config_path, config_profile)) as loader:
        return loader.load(query)
```

5. Run the block.

### Export a dataframe

Here is an example code snippet to export a dataframe to Postgres:

```python theme={null}
from mage_ai.settings.repo import get_repo_path
from mage_ai.io.config import ConfigFileLoader
from mage_ai.io.postgres import Postgres
from pandas import DataFrame
from os import path

if 'data_exporter' not in globals():
    from mage_ai.data_preparation.decorators import data_exporter


@data_exporter
def export_data_to_postgres(df: DataFrame, **kwargs) -> None:
    schema_name = 'your_schema_name'  # Specify the name of the schema to export data to
    table_name = 'your_table_name'  # Specify the name of the table to export data to
    config_path = path.join(get_repo_path(), 'io_config.yaml')
    config_profile = 'default'

    with Postgres.with_config(ConfigFileLoader(config_path, config_profile)) as loader:
        loader.export(
            df,
            schema_name,
            table_name,
            index=False,  # Specifies whether to include index in exported table
            if_exists='replace',  # Specify resolution policy if table name already exists
            allow_reserved_words=True,
            unique_conflict_method='UPDATE',
            unique_constraints=['col'],
        )

```

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