Change events (CDC)

Generate a coherent insert/update/delete history in Debezium's envelope shape — no database, no Kafka, just a file:

synth.WriteCDC[User]("changes.jsonl", 10_000, synth.CDCConfig{
    Table: "users", UpdateRate: 0.3, DeleteRate: 0.1, Snapshot: 100,
})

synth cdc -s users.yaml -o changes.jsonl -n 10000 --update-rate 0.3 --delete-rate 0.1

A row exists before it is updated, updates carry the true before image, and deleted rows are never touched again. LSNs and timestamps advance monotonically.

Soft deletes

Deletes are hard by default (op=d). Pass --soft-delete (or CDCConfig.SoftDelete) to emit them as op=u updates that stamp a deleted_at column instead, so a consumer can be tested against either workload from one spec:

synth cdc -s users.yaml -n 10000 --delete-rate 0.1 --soft-delete

Cascading across two tables

Give a child spec and the column that references the parent. Deleting a parent then deletes its children first, then the parent — the order a foreign key requires:

synth cdc -s orders.yaml --child items.yaml --child-fk order_id --delete-rate 0.2

Inserts keep integrity (a child only ever references a parent that exists), one LSN and clock run across both tables, and the stream is deterministic under the seed.

Related

Snapshots express the same history as state rather than as events — and replaying one over the other is an enforced identity.