npm package: @raphiniert/ra-data-postgrest
Description: postgREST data provider for react-admin
Latest version: 2.5.1

# PostgREST Data Provider For React-Admin
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PostgREST Data Provider for [react-admin](https://github.com/marmelab/react-admin), the frontend framework for building admin applications on top of REST/GraphQL services.

## Installation

```sh
npm install --save @raphiniert/ra-data-postgrest
```

## Citation
If you use the PostgREST Data Provider in your research or project, please consider citing the corresponding [paper](https://www.sciencedirect.com/science/article/pii/S2665963824000873). Feel free to include the following BibTeX entry in your publications:

```bibtex
@article{SCHEIBLE2024100699,
    title = {PostgREST Data Provider for React-Admin: Bootstrap the creation of user interfaces on top of PostgreSQL databases},
    journal = {Software Impacts},
    volume = {21},
    pages = {100699},
    year = {2024},
    issn = {2665-9638},
    doi = {https://doi.org/10.1016/j.simpa.2024.100699},
    author = {Raphael Scheible}
}
```


## REST Dialect

This Data Provider fits REST APIs using simple GET parameters for filters and sorting. This is the dialect used for instance in [PostgREST](http://postgrest.org).

| Method             | API calls                                                                            |
| ------------------ | ------------------------------------------------------------------------------------ |
| `getList`          | `GET http://my.api.url/posts?order=title.asc&offset=0&limit=24&filterField=eq.value` |
| `getOne`           | `GET http://my.api.url/posts?id=eq.123`                                              |
| `getMany`          | `GET http://my.api.url/posts?id=in.(123,456,789)`                                    |
| `getManyReference` | `GET http://my.api.url/posts?author_id=eq.345`                                       |
| `create`           | `POST http://my.api.url/posts`                                                       |
| `update`           | `PATCH http://my.api.url/posts?id=eq.123`                                            |
| `updateMany`       | `PATCH http://my.api.url/posts?id=in.(123,456,789)`                                  |
| `delete`           | `DELETE http://my.api.url/posts?id=eq.123`                                           |
| `deleteMany`       | `DELETE http://my.api.url/posts?id=in.(123,456,789)`                                 |

**Note**: The PostgREST data provider expects the API to include a `Content-Range` header in the response to `getList` calls. The value must be the total number of resources in the collection. This allows react-admin to know how many pages of resources there are in total, and build the pagination controls.

```
Content-Range: posts 0-24/319
```

If your API is on another domain as the JS code, you'll need to whitelist this header with an `Access-Control-Expose-Headers` [CORS](https://developer.mozilla.org/en-US/docs/Web/HTTP/Access_control_CORS) header.

```
Access-Control-Expose-Headers: Content-Range
```

## Usage

```jsx
// in src/App.js
import * as React from 'react';
import { Admin, Resource, fetchUtils } from 'react-admin';
import postgrestRestProvider,
     { IDataProviderConfig,
       defaultPrimaryKeys,
       defaultSchema } from '@raphiniert/ra-data-postgrest';

import { PostList } from './posts';

const config: IDataProviderConfig = {
    apiUrl: 'http://path.to.my.api/',
    httpClient: fetchUtils.fetchJson,
    defaultListOp: 'eq',
    primaryKeys: defaultPrimaryKeys,
    schema: defaultSchema
}

const App = () => (
    <Admin dataProvider={postgrestRestProvider(config)}>
        <Resource name="posts" list={PostList} />
    </Admin>
);

export default App;
```

### Adding Custom Headers

The provider function accepts an HTTP client function as second argument. By default, they use react-admin's `fetchUtils.fetchJson()` as HTTP client. It's similar to HTML5 `fetch()`, except it handles JSON decoding and HTTP error codes automatically.

That means that if you need to add custom headers to your requests, you just need to _wrap_ the `fetchJson()` call inside your own function:

```jsx
import { fetchUtils, Admin, Resource } from 'react-admin';
import postgrestRestProvider from '@raphiniert/ra-data-postgrest';

const httpClient = (url, options = {}) => {
    if (!options.headers) {
        options.headers = new Headers({ Accept: 'application/json' });
    }
    // add your own headers here
    options.headers.set('X-Custom-Header', 'foobar');
    return fetchUtils.fetchJson(url, options);
};

const config: IDataProviderConfig = {
    ...
    httpClient: httpClient,
    ...
}

const dataProvider = postgrestRestProvider(config);

render(
    <Admin dataProvider={dataProvider} title="Example Admin">
        ...
    </Admin>,
    document.getElementById('root')
);
```

Now all the requests to the REST API will contain the `X-Custom-Header: foobar` header.

**Tip**: The most common usage of custom headers is for authentication. `fetchJson` has built-on support for the `Authorization` token header:

```js
const httpClient = (url, options = {}) => {
    options.user = {
        authenticated: true,
        token: 'SRTRDFVESGNJYTUKTYTHRG',
    };
    return fetchUtils.fetchJson(url, options);
};
```

Now all the requests to the REST API will contain the `Authorization: SRTRDFVESGNJYTUKTYTHRG` header.

### Special Filter Feature

As postgRest allows several comparators, e.g. `ilike`, `like`, `eq`...
The dataProvider is designed to enable you to specify the comparator in your react filter component:

```jsx
<Filter {...props}>
    <TextInput label="Search" source="post_title@ilike" alwaysOn />
    <TextInput label="Search" source="post_author" alwaysOn />
    // some more filters
</Filter>
```

One can simply append the comparator with an `@` to the source. In this example the field `post_title` would be filtered with `ilike` whereas `post_author` would be filtered using `eq` which is the default if no special comparator is specified.

#### RPC Functions

Given a RPC call as `GET /rpc/add_them?post_author=Herbert HTTP/1.1`, the dataProvider allows you to filter such endpoints. As they are no view, but a SQL procedure, several postgREST features do not apply. I.e. no comparators such as `ilike`, `like`, `eq` are applicable. Only the raw value without comparator needs to be send to the API. In order to realize this behavior, just add an "empty" comparator to the field, i.e. end `source` with an `@` as in the example:

```jsx
<Filter {...props}>
    <TextInput label="Search" source="post_author@" alwaysOn />
    // some more filters
</Filter>
```

### Compound primary keys

If one has data resources without primary keys named `id`, one will have to define this specifically. Also, if there is a primary key, which is defined over multiple columns:

```jsx
const config: IDataProviderConfig = {
    ...
    primaryKeys: new Map([
        ['some_table', ['custom_id']],
        ['another_table', ['first_column', 'second_column']],
    ]),
    ...
}

const dataProvider = postgrestRestProvider(config);
```

### Custom schema
PostgREST allows to [select and switch the database schema](https://postgrest.org/en/stable/api.html#switching-schemas) by setting a custom header. Thus, one way to use this function would be adding the custom header as a string while using react-admin hooks within `meta.schema` (compare to next section) or to set it up as function of `() => (string)` while using the data provider just component based. The latter can be done as follows and gives the opportunity to use some central storage (e.g. localStorage) which can be changed at multiple points of the application:
```jsx
const config: IDataProviderConfig = {
    ...
    schema: () => localStorage.getItem("schema") || "api",
    ...
}

const dataProvider = postgrestRestProvider(config);
```

### Passing extra headers via meta
Postgrest supports calling functions with a single JSON parameter by sending the header Prefer: params=single-object with your request according to its [docs](https://postgrest.org/en/stable/api.html#calling-functions-with-a-single-json-parameter).

Within the data provider one can add any kind of header to the request while calling react-admin hooks, e.g.:

```jsx
const [create, { isLoading, error }] = useCreate(
    'rpc/my-function',
    {
        data: { ... },
        meta: { headers: { Prefer: 'params=single-object' } },
    }
);
```

### Null sort order

Postgrest supports specifying the position of nulls in [sort ordering](https://postgrest.org/en/v12/references/api/tables_views.html#ordering). This can be configured via an optional data provider parameter:

```jsx
import { PostgRestSortOrder, IDataProviderConfig } from '@raphiniert/ra-data-postgrest';

const config: IDataProviderConfig = {
    ...
    sortOrder: PostgRestSortOrder.AscendingNullsLastDescendingNullsLast
    ...
}

const dataProvider = postgrestRestProvider(config);
```

This parameter impacts the `getList` and `getManyReference` calls.

It is important to note that null positioning in sort will impact index utilization so in some cases you'll want to add  corresponding index on the database side.

You can also override this parameter on a per-query basis by passing `nullsfirst: true` or `nullslast: true` in the `meta` object of the query:

```jsx
const { data, total, isLoading, error } = useGetList(
    'posts',
    {
        pagination: { page: 1, perPage: 10 },
        sort: { field: 'published_at', order: 'DESC' },
        meta: { nullslast: true }
    }
);
```

### Vertical filtering
Postgrest supports a feature of [Vertical Filtering (Columns)](https://postgrest.org/en/stable/api.html#vertical-filtering-columns). Within the react-admin hooks this feature can be used as in the following example:

```jsx
const { data, total, isLoading, error } = useGetList(
    'posts',
    {
        pagination: { page: 1, perPage: 10 },
        sort: { field: 'published_at', order: 'DESC' }
        meta: { columns: ['id', 'title'] }
    }
);
```

Further, one should be able to leverage this feature to rename columns:
```jsx
columns: ['id', 'somealias:title']
```
, to cast columns:
```jsx
columns: ['id::text', 'title']
```
and even get bits from a json or jsonb column"
```jsx
columns: ['id', 'json_data->>blood_type', 'json_data->phones']
```

**Note**: not working for `create` and `updateMany`.

### Embeds and prefetch

`ra-data-postgrest` supports React Admin [embed](https://marmelab.com/react-admin/DataProviders.html#embedding-relationships) and [prefetch](https://marmelab.com/react-admin/DataProviders.html#prefetching-relationships) features.

For instance, here's how to prefetch posts authors (many-to-one relationship):

```jsx
import { Datagrid, List, ReferenceField, TextField } from 'react-admin';

const PostList = () => (
    <List queryOptions={{ meta: { prefetch: ['authors'] } }}>
        <Datagrid>
            <TextField source="title" />
            <ReferenceField source="author_id" reference="authors" />
        </Datagrid>
    </List>
)
```

Here's how to embed posts authors instead:

```jsx
import { Datagrid, List, ReferenceField, TextField } from 'react-admin';

const PostList = () => (
    <List queryOptions={{ meta: { embed: ['authors'] } }}>
        <Datagrid>
            <TextField source="title" />
            <TextField source="authors.name" />
        </Datagrid>
    </List>
)
```

This will result in a single query to the database and populate React Admin cache for the `authors` resource.

This works for one-to-many relationships too. For instance, here's how to prefetch all books from an author:

```jsx
import { Show, SimpleShowLayout, ReferenceManyField, Datagrid, TextField, DateField } from 'react-admin';

const AuthorShow = () => (
    <Show queryOptions={{ meta: { prefetch: ['books'] } }}>
        <SimpleShowLayout>
            <TextField source="first_name" />
            <TextField source="last_name" />
            <ReferenceManyField reference="books" target="author_id" label="Books">
              <Datagrid>
                <TextField source="title" />
                <DateField source="published_at" />
              </Datagrid>
            </ReferenceManyField>
        </SimpleShowLayout>
    </Show>
);
```

Here's how to embed the books instead:

```jsx
import { Show, SimpleShowLayout, ArrayField, Datagrid, TextField, DateField } from 'react-admin';

const AuthorShow = () => (
    <Show queryOptions={{ meta: { prefetch: ['books'] } }}>
        <SimpleShowLayout>
            <TextField source="first_name" />
            <TextField source="last_name" />
            <ArrayField source="books">
              <Datagrid>
                <TextField source="title" />
                <DateField source="published_at" />
              </Datagrid>
            </ArrayField>
        </SimpleShowLayout>
    </Show>
);
```

This will result in a single query to the database and populate React Admin cache for the `books` resource.

## Developers notes

The current development of this library was done with node v20.18.0 (npm v10.8.2). In this version the unit tests and the development environment should work.

## License

This data provider is licensed under the MIT License and sponsored by [raphiniert.com](https://raphiniert.com).