README.md
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### Deprecated
This is deprecated because it is merged with [postgraphile-polymorphic-relation-plugin](https://github.com/hansololai/postgraphile-polymorphic-relation-plugin)
# PostGraphile Connection Plugin Polymorphic
This plugin exposes nested filters created by polymorphic associations.
Polymorphic associations are defined like this [in ruby on rails](https://guides.rubyonrails.org/association_basics.html#polymorphic-associations).
## Usage
Requires postgraphile@4.2+ and the following plugins appended prior to this plugin:
- `postgraphile-plugin-connection-filter@^1.0.0`
## Feature
### Motivation
The connection filter has already come with very nice and comprehensive nested assocation filters. But it does not support polymorphic associations.
For example, if you have a tag table, that is polymorphic associated with multiple tables.
```sql
create table taggs(
id: integer primary_key,
taggable_type: text,
taggable_id: integer,
);
create table user(
id: integer,
name: text,
);
```
And a record in taggs is
```
id: 50
taggable_type: 'User'
taggable_id: 1
```
This means the tag(id:50) is connected to User record of id:1.
If you want to filter the connections like the following:
```graphql
allTaggs(filter:{
userAsTaggable:{id:1} // This does not exist in regular connection filter
}){
nodes{
id
}
}
```
and hoping to find the tag(id:50). You won't be able to do it because the `userAsTaggable` does not exist.
### What this plugin does
This plugin will create the forward relationship. (this `userAsTaggable`) field, and also the backward relationship. (the `taggs` field on User Connection, and other connections that is associated). Also if the `taggable_type` and `taggable_id` are has an unique constraint. The backward filter is not a single object filter, instead of a multi-field, which consist of three fields `some`,`every`,`none`.
### Install
```
yarn add postgraphile-plugin-connection-filter-polymorphic
```
### How to use
This plugin uses [smart comments](https://www.graphile.org/postgraphile/smart-comments/) to know the association. Originally I was planning to use a distinct query on the table to find all possible associations, but that took a long time and is not very customizable. The smart comments are on the `type` field
```
@isPolymorphic
@polymorphicTo User
@polymorphicTo Post
```
Use the previous example, where a tag is associated with User, and Post.
```sql
comment on column taggs.taggable_type is E'@isPolymorphic\n@polymorphicTo User\n@polymorphicTo Post';
```
The meta information will transfer to a {isPolymorphic:true, polymorphicTo:['User','Post]}.
Note you MUST have at least two entries for @polymorphicTo in the comment. Because otherwise it will be converted as a string, insteady of array.
## Development
To establish a test environment, create an empty PostgreSQL database and set a `TEST_DATABASE_URL` environment variable with your database connection string.
```bash
createdb graphile_test
export TEST_DATABASE_URL=postgres://localhost:5432/graphile_test
yarn
yarn test
```