Make Argus.Sync.EntityFramework provider-agnostic (support EF Core adapters beyond Postgres)

[Mercurial]

Summary

Argus.Sync.EntityFramework is named for EF Core (which is provider-agnostic) but is currently wired specifically to PostgreSQL. EF Core supports many providers — SQLite, SQL Server, MySQL/MariaDB, etc. — and the bulk of the backend is already provider-neutral, so opening it up is a contained change.

What is already provider-agnostic

CardanoDbContext, EfBlockUnitOfWork, and EfBlockUnitOfWorkFactory use only EF Core APIs (SaveChanges, transactions, the change-tracker) — no Npgsql types.

• Caveat: EfBlockUnitOfWork sets Database.AutoSavepointsEnabled = false. That is a generic EF property, but the motivation was an Npgsql quirk (auto-savepoints tripping under repeated same-transaction SaveChanges). Worth confirming the value is correct/harmless on other providers.

What is Postgres-specific today

1. Registration — EfServiceCollectionExtensions.cs hardcodes options.UseNpgsql(...) (one line).
2. Single-instance lock — PostgresSingleInstanceLockWorker is entirely NpgsqlConnection + pg_advisory_lock / pg_advisory_unlock. This is the only genuinely DB-specific component.
3. Package dependency — pulls Npgsql.EntityFrameworkCore.PostgreSQL.

Proposed approach

• Pluggable provider: add a generic registration that takes the provider setup, e.g. AddCardanoEntityFrameworkIndexer<TContext>(config, Action<DbContextOptionsBuilder> configureProvider), and keep AddCardanoPostgresIndexer<T> as a thin convenience wrapper (configureProvider = o => o.UseNpgsql(...)) so current behavior is unchanged.
• Pluggable lock: the single-instance lock already sits behind ISingleInstanceLock (core), with Postgres + Mongo implementations. For a new EF provider, either:
  • supply a native lock (SQL Server sp_getapplock, MySQL GET_LOCK, …), or
  • provide a generic EF lease-lock (a ReducerLocks row with atomic upsert + heartbeat, like the Mongo lease) as a provider-neutral default — less ideal than native advisory locks, but works on any provider.
• Packaging decision: keep Argus.Sync.EntityFramework generic with Postgres as a supported provider, vs. split the Npgsql dependency into a separate Argus.Sync.EntityFramework.Postgres.

Scope note

The unit of work and DbContext are free; the real per-provider cost is the single-instance lock (plus verifying the savepoint setting). Ship Postgres as the reference implementation and document "bring your own EF provider."

[Mercurial]

Closing for now — deferring until there's a concrete need for a non-Postgres EF provider.

The provider-agnostic plumbing landed in #179 (released as v1.3.0-alpha): Argus.Sync.EntityFramework is now provider-neutral with a public AddCardanoEntityFrameworkIndexer<T>(configureProvider) seam, and the PostgreSQL/Npgsql specifics live in a separate Argus.Sync.EntityFramework.Postgres package. So adding another EF provider is now a small sibling package rather than a fork of the core.

Deferred (the remaining work): actually shipping a non-Postgres provider (SQLite / SQL Server / MySQL). The one non-trivial piece is the single-instance lock — Postgres uses pg_advisory_lock, which other providers lack, so each needs either a native lock (sp_getapplock, GET_LOCK, …) or a generic EF lease-lock (a heartbeat row, like the Mongo backend). Reopen when a concrete provider is wanted.

[Mercurial]

Correction on the closure reason — re-closing as completed, not "not planned".

Re-reading this issue's own scope, the Proposed approach + Scope note asked for: a pluggable AddCardanoEntityFrameworkIndexer<TContext>(config, configureProvider) seam (keeping AddCardanoPostgresIndexer as a wrapper), the packaging split into Argus.Sync.EntityFramework.Postgres, and "ship Postgres as the reference implementation, document bring-your-own EF provider." All of that shipped in #179 (v1.3.0-alpha). The provider-agnostic goal is met — the core is provider-neutral and any EF Core provider can be plugged via the public seam.

Out of scope here (a separate future enhancement, not needed now): shipping a concrete in-box provider such as Argus.Sync.EntityFramework.Sqlite, plus an optional generic EF lease-lock for providers without native advisory locks. File a fresh issue if/when a specific provider is actually wanted.