implement-repository

Write SQL in a query file per aggregate, run sqlc generate with sql_package pgx/v5, and call sqlcgen.New(tx) directly in each method. The repository takes the pgx.Tx from context and never opens its own transaction.

Use an UPDATE with WHERE current_version = expected_version via sqlc :execrows, where expected_version is the event version minus one. Zero affected rows translate to a conflict sentinel, and a unique constraint on (aggregate_id, version) is the last line of defense.

The usecase owns the transaction through a tx.Manager that places pgx.Tx on the context. The repository only reads it via tx.From(ctx) and returns an error if none exists, never calling Begin, Commit, or Rollback itself.

Inspect pgconn.PgError by SQLSTATE and named constraint, then return the domain sentinel matching that constraint from a single translation table. ErrNoRows becomes a NotFound sentinel, and unlisted violations pass through untranslated with one layer of context.

Choose event-sourced persistence when the data model document defines base and detail event tables, giving the aggregate a version and Apply{Event} methods. Use plain Create/Update overwrites when only resource tables exist and the aggregate has no version.

It excludes repository interface design, transaction initiation, read models like lists and search, DDL and migration tooling, and test strategy, each delegated to its own convention. It also refuses to enforce invariants via SELECT checks, requiring DB constraints instead.