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The data indexed by a squid into a Postgres database can be automatically presented with a GraphQL API service powered by the OpenReader lib of the Squid SDK. The OpenReader GraphQL server takes the schema file as an input and serves a GraphQL API supporting OpenCRUD queries for the entities defined in the schema.

To start the API server based on the schema.graphql run in the squid project root:

npx squid-graphql-server

or, for more options,

npx squid-graphql-server

The squid-graphql-server binary supports multiple optional flags to enable caching, subscriptions, DoS protection etc. Its features are covered in the next sections.

The API server listens at port defined by GQL_PORT (defaults to 4350). The database connection is configured with the env variables DB_NAME, DB_USER, DB_PASS, DB_HOST, DB_PORT.

The GraphQL API is enabled by the api: service in the deploy section of squid.yaml for Subsquid Cloud deployments.

Supported Queries

The details of the supported OpenReader queries can be found in a separate section Query a Squid. Here is a brief overview of the queries generated by OpenReader for each entity defined in the schema file:

Union and typed JSON types are mapped into GraphQL Union Types with a proper type resolution with __typename.

Built-in custom scalar types

The OpenReader GraphQL API defines the following custom scalar types:

  • DateTime entity field values are presented in the ISO format
  • Bytes entity field values are presented as hex-encoded strings prefixed with 0x
  • BigInt entity field values are presented as strings