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Version: FireSquid

Custom Database

A custom implementation of the Database interface is a recommended solution for squids with multiple data sinks and/or for non-transactional or non-relational databases. In such a case, the inferred Store facade exposed to the handlers may provide multiple targets for persisting the data. Database.transact should handle potential edge-cases when writes to either of the data sinks fail.

In order to implement a custom adapter to a data sink, it suffices to implement the Database interface:

export interface Database<S> {
    // initialize the connection and run migrations 
    connect(): Promise<number>
    // run handlers for blocks in the range `[from, to]` in a single transaction
    // cb is the callback passed to processor.run()
    transact(from: number, to: number, cb: (store: S) => Promise<void>): Promise<void>
    // update and persist the processor status to `height`
    advance(height: number): Promise<void>
}

The interface only defines how the processor advances with the indexing and connects to the data sink. The following is left as implementation details:

  • persisting the indexing status
  • opening and rolling back the transaction (if applicable)

Consult these implementations for details: