32 lines
2.5 KiB
Markdown
32 lines
2.5 KiB
Markdown
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# Postgraphile
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You can expose VulcanizeDB data via [Postgraphile](https://github.com/graphile/postgraphile).
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Check out [their documentation](https://www.graphile.org/postgraphile/) for the most up-to-date instructions on installing, running, and customizing Postgraphile.
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## Simple Setup
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As of April 30, 2019, you can run Postgraphile pointed at the default `vulcanize_public` database with the following commands:
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```
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npm install -g postgraphile
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postgraphile --connection postgres://localhost/vulcanize_public --schema=public,custom --disable-default-mutations
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```
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Arguments:
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- `--connection` specifies the database. The above command connects to the default `vulcanize_public` database defined in [the example config](../staging/environments/public.toml.example).
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- `--schema` defines what schema(s) to expose. The above exposes the `public` schema (for core VulcanizeDB data) as well as a `custom` schema (where `custom` is the name of a schema defined in executed transformers).
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- `--disable-default-mutations` prevents Postgraphile from exposing create, update, and delete operations on your data, which are otherwise enabled by default.
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## Customizing Postgraphile
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By default, Postgraphile will expose queries for all tables defined in your chosen database/schema(s), including [filtering](https://www.graphile.org/postgraphile/filtering/) and [auto-discovered relations](https://www.graphile.org/postgraphile/relations/).
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If you'd like to expose more customized windows into your data, there are some techniques you can apply when writing migrations:
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- [Computed columns](https://www.graphile.org/postgraphile/computed-columns/) enable you to derive additional fields from types defined in your database.
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For example, you could write a function to expose a block header's state root over Postgraphile with a computed column - without modifying the `public.headers` table.
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- [Custom queries](https://www.graphile.org/postgraphile/custom-queries/) enable you to provide on-demand access to more complex data (e.g. the product of joining and filtering several tables' data based on a passed argument).
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For example, you could write a custom query to get the block timestamp for every transaction originating from a given address.
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- [Subscriptions](https://www.graphile.org/postgraphile/subscriptions/) enable you to publish data as it is coming into your database.
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The above list is not exhaustive - please see the Postgraphile documentation for a more comprehensive and up-to-date description of available features.
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