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Version: Old ArrowSquid docs

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 type Database<S> = FinalDatabase<S> | HotDatabase<S>

export interface FinalDatabase<S> {
supportsHotBlocks?: false
connect(): Promise<HashAndHeight>
transact(info: FinalTxInfo, cb: (store: S) => Promise<void>): Promise<void>
}

export interface HotDatabase<S> {
supportsHotBlocks: true
connect(): Promise<HotDatabaseState>
transact(info: FinalTxInfo, cb: (store: S) => Promise<void>): Promise<void>
transactHot(info: HotTxInfo, cb: (store: S, block: HashAndHeight) => Promise<void>): Promise<void>
}

Consult this file for details.

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: