Design notes

The condensed design and dependency record. For the user-facing architecture write-up see Architecture. The original per-workstream design specs are no longer carried in the tree; they remain in git history.

What Inquiry is

A compile-time-SQL micro-ORM: a Roslyn incremental source generator that bakes every SQL statement as a const string at build time and emits zero-allocation struct materializers. The runtime ships no SQL and no dialect type — each provider analyzer produces the right SQL flavor for its dialect when the compilation's [InquiryDialect] matches.

The feature roadmap (implemented)

The original 13-workstream roadmap is built and merged to main. It was sequenced to run as parallel git worktrees against a shared generator core:

ID	Workstream	ID	Workstream
E1	MySQL / MariaDB provider	W5	Projections + aggregations
E2	Oracle provider	W6	Optimistic concurrency / row-versioning
E3	Cloud-compat (Azure SQL / CockroachDB / Aurora retry)	W7	Migrations / schema DDL (Phase A)
W1	Richer WHERE predicates	W8	Soft deletes
W2	ORDER BY + pagination (offset + keyset)	W9	Full-text search
W3	Batch & bulk operations	W10	JSON / array / value-converter columns
W4	Automatic prepared-statement reuse

Each has a user-facing article under Features. Remaining follow-ups are on the Roadmap.

The shared "hot spine"

Nearly every workstream edits the same handful of generator files — the SqlBuilder hierarchy (+ each *SqlBuilder), StoreProcessor, StoreOperationEmitter, EntityProcessor, the column/operation models, and the diagnostic registry. Naive parallelism collides there. The project's answer:

Foundation-first. A serialized foundation pass turned the hot spine into stable extension points (init-only column metadata added additively; a single AppendWhere primitive through which key, concurrency, soft-delete, and filter predicates AND-compose; a shared MaterializerEmitter; a reserved diagnostic-ID registry). Only then do the feature workstreams fan out.
virtual-with-base-default over abstract. New SqlBuilder capabilities default in the base where the SQL is dialect-uniform, so a new provider inherits them and overrides only what differs. An abstract member breaks every provider's build until implemented, so it's used only when there's no portable default.
Append-only edits to the operation/diagnostic enums and registration arrays, so parallel branches merge textually. See Adding a provider for the append-point checklist.

Live-runtime testing & benchmarks

Per-dialect compilation. Each provider test project link-compiles the shared Northwind source under its own analyzer, so it tests that engine's real generated SQL — not a mock.
Testcontainers, skip-without-Docker. One container per provider test assembly (via Testcontainers); every live fact uses SkippableFact and skips gracefully when Docker is absent.
Schema-fidelity guardrail. Inquiry.IntegrationTesting holds the canonical expected-Northwind schema, a schema-fidelity comparator, and an ISchemaIntrospector per engine; the generated DDL (InquiryGeneratedSchema.Ddl) is verified to stand up on each live engine and to match the expected structure (tables + primary keys + foreign keys).
Apples-to-apples benchmarks. BenchmarkDotNet suites compare ADO.NET / Inquiry / Dapper / EF Core on the same operations, in-process on SQLite and per-dialect (PostgreSQL / MySQL / SQL Server / Oracle) over Testcontainers. The generated-store read overloads stream with CommandBehavior.SequentialAccess (generated materializers read each column once, in ascending order), bringing large-read allocation to raw-ADO levels. Headline: Inquiry allocates at raw-ADO levels (lowest of any wrapper); EF Core is several times higher.

Out of scope (by design)

Migrations Phase B (schema diff / ALTER / versioning) — delegate to DbUp or FluentMigrator; Inquiry generates the initial CREATE TABLE DDL only.
NoSQL / document engines (Cosmos DB, MongoDB) — they don't fit a SQL-generating, schema-bound model.
JOIN-based or lazy eager loading — the separate-query model is the recommended high-performance pattern; it is not considered a gap.