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fix(query): preserve discriminator predicates in type filters #263

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9ffd311
feat(query): support inheritance discriminator filters
j-d-ha Jun 24, 2026
7e76384
docs(query): document inheritance type filtering
j-d-ha Jun 24, 2026
7059be0
docs(skills): require spec work on feature branches
j-d-ha Jun 24, 2026
8309363
feat(test): add SQL assertions to inheritance query tests
j-d-ha Jun 24, 2026
77da5ce
feat(query): enhance `OfType<T>` queries with SQL assertions and pred…
j-d-ha Jun 24, 2026
bef4635
fix(query): preserve discriminator predicates in type filters
j-d-ha Jun 24, 2026
6c3dc0d
Merge branch 'main' into test/tests-inheritance-query-spec
j-d-ha Jun 24, 2026
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35 changes: 20 additions & 15 deletions docs/limitations.md
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Expand Up @@ -34,19 +34,19 @@ request is sent.

See [Supported Operators](querying/operators.md) for the full list of what does translate.

| Category | Operators | Why |
| --------------------------------------- | ---------------------------------------------------------------------------- | -------------------------------------------------------------------------------------------------- |
| Aggregation | `Count`, `LongCount`, `Sum`, `Average`, `Min`, `Max` | DynamoDB PartiQL has no aggregate functions |
| Grouping | `GroupBy` | `GROUP BY` is not supported in DynamoDB PartiQL |
| Joins | `Join`, `GroupJoin`, `LeftJoin`, `RightJoin`, `SelectMany`, `DefaultIfEmpty` | DynamoDB does not support cross-item joins |
| Set operations | `Union`, `Concat`, `Except`, `Intersect` | Not supported in DynamoDB PartiQL |
| Offset / paging | `Skip`, `Take`, `ElementAt`, `ElementAtOrDefault` | DynamoDB has no offset semantics — use `Limit(n)` for an evaluation budget |
| Element operators | `Any`, `All` | Not supported server-side |
| Reverse traversal | `Last`, `LastOrDefault`, `Reverse` | Requires reverse index traversal, not implemented |
| Deduplication | `Distinct` | `SELECT DISTINCT` is not supported in DynamoDB PartiQL |
| Type filtering | `OfType<T>`, `Cast<T>` | Not supported |
| Conditional skipping | `SkipWhile`, `TakeWhile` | Not supported |
| Queryable `Contains` over query sources | `Queryable.Contains(dbSet, item)` | Not supported; in-memory membership translates to `IN`, native collection membership to `contains` |
| Category | Operators | Why |
| --------------------------------------- | ---------------------------------------------------------------------------- | ----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| Aggregation | `Count`, `LongCount`, `Sum`, `Average`, `Min`, `Max` | DynamoDB PartiQL has no aggregate functions |
| Grouping | `GroupBy` | `GROUP BY` is not supported in DynamoDB PartiQL |
| Joins | `Join`, `GroupJoin`, `LeftJoin`, `RightJoin`, `SelectMany`, `DefaultIfEmpty` | DynamoDB does not support cross-item joins |
| Set operations | `Union`, `Concat`, `Except`, `Intersect` | Not supported in DynamoDB PartiQL |
| Offset / paging | `Skip`, `Take`, `ElementAt`, `ElementAtOrDefault` | DynamoDB has no offset semantics — use `Limit(n)` for an evaluation budget |
| Element operators | `Any`, `All` | Not supported server-side |
| Reverse traversal | `Last`, `LastOrDefault`, `Reverse` | Requires reverse index traversal, not implemented |
| Deduplication | `Distinct` | `SELECT DISTINCT` is not supported in DynamoDB PartiQL |
| Type casting | `Cast<T>` | Not supported; TPH discriminator filtering via `OfType<TDerived>()` and `is` requires active discriminator metadata; `GetType()` checks require active discriminator metadata and are limited to exact concrete mapped entity types |
| Conditional skipping | `SkipWhile`, `TakeWhile` | Not supported |
| Queryable `Contains` over query sources | `Queryable.Contains(dbSet, item)` | Not supported; in-memory membership translates to `IN`, native collection membership to `contains` |

Value-converted enum numeric casts are also rejected when compared to parameters. For example, `(int)entity.Status == value` is not translated if `Status` uses `.HasConversion<string>()`, because DynamoDB stores the converted string value. Compare `entity.Status` to an enum value directly, or map the enum numerically.

Expand Down Expand Up @@ -396,8 +396,13 @@ provider cannot guarantee auto-increment semantics on DynamoDB item writes.

### Shared-Table Discriminator Constraints

When multiple entity types share the same DynamoDB table, a discriminator is required. The
following constraints are validated at startup:
When multiple entity types share the same DynamoDB table, discriminator metadata is required only
when the provider needs server-side type discrimination or type filtering. `HasNoDiscriminator()`
can disable discriminator metadata for a shared-table group when your key design already isolates
entity types. With discriminator metadata disabled, derived `OfType<T>()`, `is`, and `GetType()`
type filters cannot be translated.

When discriminator metadata is enabled, the following constraints are validated at startup:

- Discriminator values must be unique within the table group.
- All entity types in the group must use the same discriminator attribute name.
Expand Down
30 changes: 27 additions & 3 deletions docs/modeling/single-table-design.md
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Expand Up @@ -248,10 +248,34 @@ For key-shape examples, continue with [Practical single-table pattern](#practica
Base queries materialize polymorphically (`DbSet<Person>` can return `Employee` and `Manager`).
When discrimination is active, the discriminator attribute is included in projection.

### `OfType<TDerived>()` limitation
### Type filtering

`Queryable.OfType<TDerived>()` is not currently translated by the provider.
Query derived sets directly (for example `context.Employees`) instead.
`Queryable.OfType<TDerived>()` translates to a discriminator predicate for TPH hierarchies:

```csharp
context.People
.OfType<Employee>()
.Where(x => x.Pk == "TENANT#1")
.ToListAsync();
```

Type tests in predicates also translate when they can be expressed as discriminator checks:

```csharp
context.People.Where(x => x is Manager);
context.People.Where(x => x.GetType() == typeof(Employee));
```

`GetType()` comparisons are exact-type checks. Use them for concrete mapped leaf types, such
as `Employee` in the example above. For base or intermediate type matching, use `is` or
`OfType<T>()`.

When `HasNoDiscriminator()` disables discrimination for a shared-table group, derived
`OfType<T>()`, `is`, and `GetType()` type filters cannot be translated to server-side type
predicates. Use key predicates or query the concrete `DbSet` directly when your PK/SK pattern
already isolates types.

`Cast<T>()` is not translated.

!!! tip "Index selection with inheritance/shared-table queries"

Expand Down
3 changes: 2 additions & 1 deletion docs/querying/operators.md
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Expand Up @@ -32,6 +32,7 @@ _This page is the authoritative reference for which LINQ operators translate to
| `string.Length` | `size(attr)` | DynamoDB `size` semantics; for strings, use with care when non-ASCII text matters |
| `string.IsNullOrEmpty(s)` | `attr IS NULL OR attr IS MISSING OR attr = ''` | Matches DynamoDB `NULL`, missing attributes, or empty string |
| `collection.Contains(prop)` | `prop IN [?, ...]` | In-memory collection membership; max 50 PK values, 100 non-key values |
| `OfType<TDerived>()` | discriminator predicate | TPH inheritance only; filters by concrete discriminator values for the requested derived type. `x is TDerived` translates when the target type can be expressed as discriminator values. `x.GetType() == typeof(TConcrete)` translates only for exact concrete mapped entity types. |

## Projection Operators

Expand Down Expand Up @@ -105,7 +106,7 @@ The following operators are not supported and throw `InvalidOperationException`
| Joins | `Join`, `GroupJoin`, `SelectMany`, `LeftJoin`, `RightJoin`, `DefaultIfEmpty` | DynamoDB does not support cross-item joins |
| Set operations | `Union`, `Concat`, `Except`, `Intersect` | Not supported |
| Conditional filtering | `SkipWhile`, `TakeWhile` | Not supported |
| Type filtering | `OfType<T>`, `Cast<T>` | Not supported |
| Type casting | `Cast<T>` | Not supported; use TPH inheritance queries with `OfType<TDerived>()` for type filtering |

## Scalar Type Support

Expand Down
22 changes: 11 additions & 11 deletions docs/spec-test-coverage.md
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Expand Up @@ -166,16 +166,16 @@ These tests use non-Northwind models and fixtures.

### Implemented

| Test Class | Methods | Cosmos | MongoDB | Notes |
| -------------------------- | ------: | :----: | :-----: | --------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `ComplexTypeQueryTestBase` | 74 | ✓ | ✗ | All inherited methods are registered/overridden with explicit outcomes; supported projection/filter, nested struct projection, and complex equality subsets execute, while navigation, set-operation, GroupBy, subquery/Contains, and pushdown cases are explicitly skipped |
| Test Class | Methods | Cosmos | MongoDB | Notes |
| -------------------------- | ------: | :----: | :-----: | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| `ComplexTypeQueryTestBase` | 74 | ✓ | ✗ | All inherited methods are registered/overridden with explicit outcomes; supported projection/filter, nested struct projection, and complex equality subsets execute, while navigation, set-operation, GroupBy, subquery/Contains, and pushdown cases are explicitly skipped |
| `InheritanceQueryTestBase` | 52 | ✓ | ✗ | Single-table inheritance with discriminator predicates is covered, including `OfType`, `is`, `GetType()` leaf checks, derived-property filters, and discriminator projections. Skips remain for keyless views, navigations/includes, transactions, set operations, non-key ordered result assumptions, scan-like `Single`, and a few unsupported projection/query shapes. |

### Future

| Test Class | Methods | Cosmos | MongoDB | Feasibility | Rationale |
| -------------------------------------------- | ------: | :----: | :-----: | ----------: | ----------------------------------------------------------------------------------------------------------------------- |
| `AdHocComplexTypeQueryTestBase` | 13 | ✓ | ✗ | ~65% | Ad-hoc complex type query scenarios; same fixture dependency |
| `InheritanceQueryTestBase` | 52 | ✓ | ✗ | ~60% | Single-table inheritance with discriminator; DynamoDB has discriminator support |
| `FiltersInheritanceQueryTestBase` | 11 | ✗ | ✗ | ~55% | Query filters on inherited types |
| `FunkyDataQueryTestBase` | 19 | ✗ | ✗ | ~60% | Edge-case strings (null chars, Unicode, SQL injection chars); WHERE translation should handle these |
| `PrimitiveCollectionsQueryTestBase` | 156 | ✓ | ✗ | ~50% | DynamoDB LIST/SET attribute querying; PartiQL supports `CONTAINS` on lists; complex collection operations not supported |
Expand Down Expand Up @@ -316,7 +316,7 @@ ______________________________________________________________________
| Non-Query (top-level) | 18 classes / 356 methods | — | 4 classes / 410 methods | 21 classes / 1,058 methods |
| BulkUpdates | — | — | 5 classes / 135+ methods | 1 class / 33 methods |
| Northwind Query | 8 classes / 458 methods | — | 1 class / 469 methods | 13 classes / 929+ methods |
| Other Query | 1 class / 74 methods | — | 10 classes / 381 methods | 18 classes / 1,691 methods |
| Other Query | 2 classes / 126 methods | — | 9 classes / 329 methods | 18 classes / 1,691 methods |
| Associations | 3 classes / 42 methods | — | 2 classes / 4 methods | 13+ classes / 123+ methods |
| Translations | 5 classes / 134 methods | — | 8 classes / 162 methods | 3 classes / 25 methods |

Expand Down Expand Up @@ -351,6 +351,7 @@ This list records recently completed additions; authoritative implemented/not-im
21. `StringTranslationsDynamoTest` — 100 methods
22. `ComplexPropertiesStructuralEqualityDynamoTest` — 16 methods
23. `ComplexPropertiesProjectionDynamoTest` — 20 methods
24. `InheritanceQueryDynamoTest` — 52 methods

### Near-term (small, high confidence)

Expand All @@ -362,16 +363,15 @@ No medium-term specification test classes are currently queued here.

### Long-term (after core coverage is stable)

1. `InheritanceQueryDynamoTest` — blocked on `OfType`, `is`/`GetType()` discriminator translation, and fixture work
2. `PrimitiveCollectionsQueryDynamoTest`
3. `BulkUpdates` family — blocked on `ExecuteUpdate`/`ExecuteDelete`
4. Remaining translation tests (Math, ByteArray)
1. `PrimitiveCollectionsQueryDynamoTest`
2. `BulkUpdates` family — blocked on `ExecuteUpdate`/`ExecuteDelete`
3. Remaining translation tests (Math, ByteArray)

### Current totals

| Status | Classes | Methods |
| -------------- | ------: | ------: |
| Implemented | 35 | 1,064 |
| Implemented | 36 | 1,116 |
| Implement Next | 0 | 0 |
| Future | 30 | 1,561+ |
| Future | 29 | 1,509+ |
| Skip | 69+ | 3,859+ |
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