Sylin.Koan.Data.Core

Sylin.Koan.Data.Core

Data access core for Koan: common primitives, options, and helpers used by relational/document/vector providers and apps.

• Target framework: net10.0
• License: Apache-2.0

Capabilities

• Entity contracts and helpers for aggregate storage
• Options and conventions shared across data adapters
• Data-owned adapter option binding for readiness and default paging
• Immutable named-source lifecycle/access policy enforced before readiness or provider work
• Separate host-owned reachability, declared-shape validation, and authorized provisioning stages
• Source-only inspection and registered reads without an Entity repository shim
• Bounded provider-neutral RecordSet materialization and compiled ordinal DTO projection
• Compact provider-neutral aggregate mapping with host-scoped compiled plans and shared physical encodings
• Selection-aware health semantics for data connectors
• Support for paging, streaming, and batching semantics (see references)

Install (minimal setup)

dotnet add package Sylin.Koan.Data.Core

Usage - quick examples

Constrained generated endpoints automatically use Data's insert-only terminal when their visible read cannot find the submitted identity. The elected adapter must support native atomic insertion; no application registration or new Entity verb is required. Existing Save remains an upsert. A conflicting insert exposes no prior row and runs no completion lifecycle. This does not make authorized updates conditional on their earlier read or provide atomic mixed bulk writes.

• Prefer first-class model statics for top-level data access in your app models:
  • Item.All(ct)
  • Item.Query(predicate, ct)
  • Item.FirstPage(size, ct) and Item.Page(pageNumber, pageSize, ct)
  • Item.QueryStream(predicate, ct)
• AllStream/QueryStream lazily compose numbered pages only when the selected adapter proves provider-bounded paging and complete ordering. Otherwise they reject correctively before query/yield; there is no materializing fallback. batchSize bounds Koan-visible candidates, not opaque driver buffers. No public cursor or resume-token API exists.
• If a first-class static isn’t available, you can fall back to the generic facade (second-class): Data<TEntity, TKey>.Query(...).

Host-owned persistence policy composes beside the normal zero-configuration bootstrap:

services.AddKoan(() =>
    Item.Lifecycle.BeforeUpsert(context =>
        context.Current.Price < 0
            ? context.Cancel("Price cannot be negative.", "item.price")
            : context.Proceed()));

The same Lifecycle boundary governs Entity/Data calls and generated REST/MCP entity operations. See /docs/reference/data/entity-lifecycle.md for phases, bulk/transaction semantics, and deliberate bypasses.

Use a named source when the application needs to inspect or query an external system without adopting Entity persistence. The connector supplies the final native binding leaf; the application declares the business name, parameters, lane, and bounds once:

services.AddKoan(koan =>
{
    koan.Data.Source("LegacyErp")
        .Query("orders.recent", query => query
            .Lane("Reports")
            .Sql("select ... where CREATED_UTC >= @since")
            .Parameter<DateTimeOffset>("since")
            .MaxRecords(500));
});

var source = Data.Source("LegacyErp");
var description = source.Describe();
var explanation = source.Explain("orders.recent");
var diagnosis = await source.Doctor(ct);
var recent = await source.Query("orders.recent", new { since }, ct);
var orders = recent.Project<RecentOrder>();
var containers = await source.Inspect().Containers(50, ct: ct);

The runtime call cannot change the provider payload, source, or read lane. Opaque bindings require a provider-enforced read lane. Inspection uses neutral containers rather than schemas/tables, and RecordSet preserves duplicate fields, missing/null, nested values, explicit bounds, and honest completion. Describe and Explain are pure and never activate a client; Doctor is explicit, bounded, non-mutating, and returns stable corrective findings.

Map an Entity to an external record shape in the same source declaration:

services.AddKoan(koan =>
{
    koan.Data.Source("LegacyErp").Map<Customer>(map => map
        .Container("dbo", "CUSTOMER")
        .Key(customer => customer.Id).Name("CUSTOMER_NO")
        .Property(customer => customer.Name.Full).Name("DISPLAY_NM")
        .Property(customer => customer.Profile).Object("PROFILE_JSON"));
});

Name is a scalar physical value, Object keeps one logical subtree together, and Path("NAME_DATA", "full") places a flat logical value inside a structured physical value. Key(...).Parts(...), Generated, ReadOnly, and Codec remain explicit only when needed.

When insert/update distinction matters, ask for it explicitly; ordinary Save stays the low-ceremony default:

var result = await item.SaveWithOutcome(ct);
// result.Outcome is Inserted or Updated; result.CommitOutcome is Committed.

This stronger path is available only when the selected adapter proves exact native mutation outcomes. Bulk writes prepare the complete Entity set, dispatch once, and reject an inexact affected-count receipt without replay.

Child relationships are strict by default. Native and in-memory providers execute directly; a scan-backed provider fails with a corrective RelationshipQueryRejectedException unless the call chooses a finite budget:

var children = await todo.GetChildren<TodoItem>(
    RelationshipQueryPolicy.Bounded(maxCandidates: 1_000, maxResults: 200), ct);

This policy bounds candidates before rows escape and never returns a partial relationship.

Load every declared direct edge with the same Relatives operation for one Entity, a finite selection, or a provider-bounded stream. Model and key types are inferred:

var graph = await todo.Relatives(ct);
var graphs = await todos.Where(todo => !todo.IsCompleted).Relatives(ct);

await foreach (var current in Todo.QueryStream(todo => !todo.IsCompleted).Relatives(ct))
{
    // current.Entity, current.Parents, current.Children
}

Finite and stream forms preserve source order and multiplicity. Parent edges use batched keyed reads; child edges retain the same strict or explicitly bounded negotiation and runtime facts as GetChildren<TChild>.

Required Entity/Data operations without a usable Koan host throw KoanHostContextException. Its Failure, Operation, and RequiredService properties distinguish an absent host, a disposed host, and a host where the Data module was not composed.

EntityContext is deliberately Data-specific: it scopes source, adapter, partition, cache, and transaction routing. It stores that state in Core's logical-flow KoanContext, but it is not the generic API for tenancy, subjects, or other module-owned axes. Those modules own their business-facing facades and register durable carriage independently through Koan.Core.Context.

Named sources default to Managed + ReadWrite. Integrate an existing system without granting Koan shape or data mutation authority by declaring the two independent ceilings once:

{
  "Koan": {
    "Data": {
      "Sources": {
        "LegacyErp": {
          "Adapter": "sqlserver",
          "ConnectionString": "<provider-enforced read-only route>",
          "StorageLifecycle": "External",
          "Access": "ReadOnly"
        }
      }
    }
  }
}

Entity, batch, instruction, and Direct paths consume the same immutable source plan. ReadOnly blocks data writes; External independently blocks create/alter/drop/repair. Forbidden and opaque effects reject before lifecycle callbacks, readiness, resource creation, or provider I/O. Provider credentials remain the security boundary.

For a synchronous console process, new ServiceCollection().StartKoan() starts a standard .NET Generic Host and returns its active provider facade. The caller owns it; use using var app = (IDisposable)services.StartKoan() so disposal stops hosted capabilities and releases the ambient Koan host binding. ASP.NET Core and workers continue to use their native host builder with AddKoan().

Boundaries and failures

• Data Core is the Entity runtime and provider-election owner; it does not provide storage by itself. Reference a connector or use the JSON floor carried by a Koan entry bundle.
• Its dependency on Cache Abstractions is inert contract vocabulary. Referencing Data Core does not activate caching.
• Stream-shaped Entity APIs run only when the elected provider proves bounded paging. Unsupported providers reject before yielding instead of hiding whole-source materialization.
• Query lifecycle callbacks observe only the final visible rows after residual filtering, sort/page completion, and projection; discarded provider candidates never escape through Lifecycle.
• Atomic batches and exact per-item outcomes are negotiated execution seams. RequireAtomic rejects before deferred mutation loads or callbacks when the selected adapter cannot prove it.
• Relationship expansion is direct-edge and budgeted. It is not recursive graph traversal, snapshot isolation, or a promise that scan-backed providers can execute without an explicit candidate limit.
• EntityContext owns Data routing dimensions only; tenancy, subject, and other semantic axes are contributed and enforced by their owning modules.
• Canonical PatchPayload is provider-neutral. Web/MCP projections own protocol parsing and normalization before the operation reaches Data.
• Required Entity operations without a live composed host throw KoanHostContextException with the missing operation/service correction.
• A business operation is never treated as a missing-shape probe, provisioned from exception text, and replayed. Adapters translate native types/codes through the Data failure-classification seam.
• Registered reads are uncached and never replayed. Unknown effects, missing/unenforced lanes, parameter drift, scalar cardinality drift, extra result channels, and active segmentation reject before unsafe exposure.
• Direct typed ADO queries share RecordSet's compiled ordinal projection; they do not serialize dictionaries to JSON.

Customization

• Configuration and advanced usage are documented in TECHNICAL.md.

References

• Data access patterns
• Provider-bounded Entity streams
• Engineering guardrails
• Repo: https://github.com/sylin-org/koan-framework

Enum storage contract

Default Entity storage preserves enum names as strings, including nullable values, nested values, collections, and declared EnumMember aliases. Unnamed numeric values fail instead of silently changing the storage format. Queries use the same spelling. Ordinary enum ordering uses declared ordinal ranks in native expressions while the stored value stays a string; native ordering of arbitrary Flags combinations rejects correctively. An explicit external mapping codec remains responsible for its declared physical representation. Existing numeric rows or columns require a separate, explicit migration; upgrades do not rewrite them automatically.

Counterpart reads

Use Entity.AllWithCount(QueryDefinition.All.Where(Filter.SameIdIn<T>(policy, ""))) when content must have an eligible same-ID counterpart in the default partition. Set the content partition on QueryDefinition. Ordinary lambda and JSON query overloads AND their predicate with the structured filter. QueryStream accepts QueryDefinition for the same provider-bounded path. Both operands retain Data source and isolation guards; unsupported native shapes reject. Count and page share predicate meaning, not a transactional snapshot.

Explicit empty partitions select default in structured reads and positional Entity Get/GetMany helpers; null retains the ambient partition. The caller's scope is restored after execution.

Guarded replacement

await replacement.ReplaceIf(stored => stored.Revision == expected, partition: locale, ct: ct) replaces an existing row only when its native guard matches. False means missing or conflict; it never inserts; Data dispatches once. Existing bounded failed-compare retries remain adapter behavior. Null partition inherits, empty selects default. The guard is captured when called, before asynchronous preparation. Ordinary Save retains upsert behavior.

Use a qualified connector and an ordinary persisted revision field. Unsupported native predicates, variants and active managed/read scopes refuse. BeforeUpsert may run on conflict; AfterUpsert runs only after success. A cancellation, cache error or lifecycle exception after dispatch does not imply rollback. This protects one destination row, not equality with another document at commit time.