This is a sample project generated by hydra-cli scaffold. Experiment by modifying schema.graphql and the mappings in the mappings folder.

• Node v14x
• Docker

# The dependencies setup relies on de-duplication, use `ci` to get everything right
npm ci

# Start a postgres instance
docker-compose up db # add optional -d flag to detach from terminal

# Apply migrations related to the processor's state keeping tables
npm run processor:migrate

# Apply the project's migrations
npm run db:migrate

# Now you can start processing chain data
npm run processor:start

# The above command will block
# Open a separate terminal and launch the graphql server to query the processed data
npm run query-node:start

Hydra tools expect a certain directory layout:

• src/generated - model/server definitions created by codegen. Do not alter the contents of this directory manually.
• src/server-extension - module with custom type-graphql based resolvers
• src/types - data type definitions for chain events and extrinsics created by typegen.
• src/mappings - mapping module.
• lib - compiled js files. The structure of this directory must reflect src.
• .env - hydra tools are heavily driven by environment variables defined here or supplied by a shell.

If you do not plan to extend GraphQl server you can delete server-extension module and then remove type-graphql and class-validator dependencies.

If you modified schema.graphql:

# Run codegen to re-generate model/server files
npm run codegen

# Analyze database state and create a new migration to match generated models
npm run db:create-migration # add -n "myName" to skip the migration name prompt

# Apply the migrations
npm run db:migrate

You might want update the Initial migration instead of creating a new one (e.g. during the development phase when the production database is not yet set up). In that case it convenient to reset the database schema and start afresh:

rm db/migrations/LastUnappliedMigration.ts
npm run db:reset
npm run db:create-migration
npm run db:migrate

To generate new type definitions for chain events and extrinsics:

# Review typegen section of manifest.yml (https://docs.subsquid.io/hydra-typegen)

# Delete old definitions
rm -rf src/types

# Run typegen tool
npm run typegen

It is recommended to use a readily set up indexer if available. It takes some time for a freshly started indexer to get in sync with chain and catch the events.

Have a look at ./indexer/docker-compose.yml for an example of how you can set up a self-hosted version.

For more details, please check out https://docs.subsquid.io.