Persisted Event Store

A PersistedEventStore is used to back the CqrsFramework and handle the storing and loading of aggregates (including domain events) in a database. The PersistedEventStore relies on a PersistedEventRepository for the actual database access of events and snapshots. For the postgres-es crate this is implemented by a PostgresEventRepository which in turn relies on a database connection pool.

Creating a PostgresEventRepository

#![allow(unused)]
fn main() {
fn configure_repo() -> PostgresEventRepository {
    let connection_string = "postgresql://test_user:test_pass@localhost:5432/test";
    let pool: Pool<Postgres> = default_postgress_pool(connection_string).await;
    PostgresEventRepository::new(pool)
}
}

The default repository will expect to find tables named events and snapshots, but the table names are configurable. To create these tables in a PostgreSql database (see database initialization files for other repository crates):

CREATE TABLE events
(
    aggregate_type text                         NOT NULL,
    aggregate_id   text                         NOT NULL,
    sequence       bigint CHECK (sequence >= 0) NOT NULL,
    event_type     text                         NOT NULL,
    event_version  text                         NOT NULL,
    payload        json                         NOT NULL,
    metadata       json                         NOT NULL,
    timestamp      timestamp with time zone DEFAULT (CURRENT_TIMESTAMP),
    PRIMARY KEY (aggregate_type, aggregate_id, sequence)
);

CREATE TABLE snapshots
(
    aggregate_type   text                                 NOT NULL,
    aggregate_id     text                                 NOT NULL,
    last_sequence    bigint CHECK (last_sequence >= 0)    NOT NULL,
    current_snapshot bigint CHECK (current_snapshot >= 0) NOT NULL,
    payload          json                                 NOT NULL,
    timestamp        timestamp with time zone DEFAULT (CURRENT_TIMESTAMP),
    PRIMARY KEY (aggregate_type, aggregate_id, last_sequence)
);

Note that the snapshots table is not needed for pure event sourcing.