jerryshao commented on code in PR #10720: URL: https://github.com/apache/gravitino/pull/10720#discussion_r3146846552
########## design-docs/iceberg-supported-nested-namespace.md: ########## @@ -0,0 +1,573 @@ +<!-- + Licensed to the Apache Software Foundation (ASF) under one + or more contributor license agreements. See the NOTICE file + distributed with this work for additional information + regarding copyright ownership. The ASF licenses this file + to you under the Apache License, Version 2.0 (the + "License"); you may not use this file except in compliance + with the License. You may obtain a copy of the License at + + http://www.apache.org/licenses/LICENSE-2.0 + + Unless required by applicable law or agreed to in writing, + software distributed under the License is distributed on an + "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY + KIND, either express or implied. See the License for the + specific language governing permissions and limitations + under the License. +--> +# [Iceberg REST] Supported Nested Namespace Design + +## Background + +This document describes one practical solution to support Iceberg nested namespaces in Gravitino. +The scope is not only UI privilege granting, but also namespace mapping, identifier handling, +authorization scope, and compatibility behavior across Iceberg REST and Gravitino. + +References: + +- https://github.com/apache/gravitino/blob/main/docs/security/access-control.md +- https://github.com/apache/gravitino/blob/main/docs/iceberg-rest-service.md +- https://github.com/apache/gravitino/blob/main/docs/manage-relational-metadata-using-gravitino.md +- https://github.com/apache/gravitino/discussions/7296 + +## Goal + +- Support nested namespace operations from Iceberg REST to Gravitino through schema mapping. +- Support privilege granting for different nested namespace scopes (including UI workflow). +- Keep metadata model stable and avoid heavy refactor. + + +## Solution Options + +### Option A: Add a new metadata object `NestedNamespace` + +Use a new metadata object `NestedNamespace` to represent nested namespace explicitly. +`NestedNamespace` has a one-to-one mapping with Iceberg `Namespace` to avoid ambiguity +with existing Gravitino `Namespace` concepts. + +Catalog -> NestedNamespace a -> NestedNamespace a.b -> Table a.b.c + -> NestedNamespace a.c -> NestedNamespace a.c.d -> Table a.c.d.e + +Pros: + +- Clearer concept modeling. + +Cons: + +- Large refactor across metadata model, API, authorization, and UI. + +### Option B (Recommended): Reuse `Schema` entity and enhance schema expression capability + +Keep physical metadata unchanged (still persisted as `Schema`) and introduce +`HierarchicalSchema` as a logical expression layer in Iceberg REST adaptation, +identifier rendering, and authorization scope matching. + +Pros: + +- Low-impact evolution path without introducing a new metadata entity. +- Decouples nested namespace semantics from `.` and reduces parser ambiguity. +- Reuses existing metadata and authorization model to reduce implementation risk. + +Cons: + +- Requires explicit conversion rules between logical path and physical schema name. +- Authorization matching and identifier serialization become more complex. +#### Option B Separator: Configurable logical separator (default `:`) + +Examples: + +- `A:B:C` as logical `HierarchicalSchema` path when separator is `:`. +- Physical schema name remains mapped through conversion layer. + +Pros: + +- Better readability than escaping `.` in many clients and UI forms. +- Lower routing conflict risk than `/`. +- Easier to keep backward compatibility with existing non-nested schema handling. + +Cons: + +- Needs clear validation rule to avoid ambiguity with existing schema names containing configured + separator. + +## Design + +### Identifier Rules + +- Introduce logical identifier concept: `HierarchicalSchema`. +- `HierarchicalSchema` uses a configurable logical separator (default `:`) in API/logic layer. +- For Gravitino REST create/update schema APIs, `request.getName()` keeps the logical schema name + and may contain `:` (for example `A:B` or `A:B:C`). +- Before persisting to `EntityStore`, schema path is normalized to `.`-separated physical schema + name. +- Escaping strategy: each path segment is encoded before physical flattening to avoid ambiguity. +- Configured logical separator is reserved as hierarchy separator and is not allowed inside one + namespace segment. +- `.` inside one segment is allowed and must not be treated as hierarchy separator. +- Parsing is direct split/join by configured logical separator at API boundary. +- Keep flat storage model and convert `HierarchicalSchema` path to physical schema name by mapping rules. +- Identifier rendering rule: + - Use encoded `HierarchicalSchema` path directly in schema position. + - Do not rely on single-quote wrapping for schema disambiguation in this phase. + +Examples: + +- Nested namespace `A:B` maps to logical `HierarchicalSchema` path `A:B` (assuming configured + separator is `:`). +- Nested namespace `A:B:C` maps to logical `HierarchicalSchema` path `A:B:C` (assuming configured + separator is `:`). +- Logical `HierarchicalSchema` path is then converted to physical schema name through mapping rules. +- Namespace levels `["team", "sales"]` are serialized using configured separator, e.g. + `team:sales`. +- Parsing `team:sales` returns `["team", "sales"]` when separator is `:`. +- Identifier rendering example: + - `metalake.catalog.A:B.table1` + - `metalake.catalog.team:sales.table2` +- In UI display and API transport, use logical path directly (for example `A:B:C`). + +### Physical Name Mapping and Reversibility + +- **Persisted schema name in `EntityStore` always uses `.` as the internal storage separator** for + stable storage semantics. +- External request/response handling uses configured logical separator and converts at API boundary. +- Connector-facing behavior remains Iceberg-compatible and does not require users to configure or + input internal storage representation. +- Mapping must be reversible: + - `logical path segments` -> `encode each segment` -> `join by '.'` for physical storage. + - physical schema name -> `split by '.'` -> `decode each segment` -> logical path segments. + - This avoids ambiguity when one segment contains `.` (for example `my.schema`). + +### Existing Name Compatibility and Migration Guard + +- Before enabling nested namespace mode for a catalog, run a pre-check scan on existing schema names + against configured logical separator. +- If existing schema names conflict with selected separator, enabling is rejected with actionable + error and user can choose another separator or rename conflicting schema names. +- Once nested mode is enabled for a catalog, creating new schema names containing configured logical + separator as plain text is rejected. + +### Delimiter Configuration Policy + +- Logical separator is configurable (for example `:`, `;`, `$`) and can be chosen to avoid conflict + with existing names. +- Physical separator in storage remains fixed as `.`. +- Recommended: keep logical separator stable after nested namespace is enabled for a catalog. +- Delimiter is configured at server level for nested-namespace parsing behavior. + +Two delimiter-governance options are under evaluation: + +- **Option 1 (restricted delimiter set)**: + - Server only accepts delimiters from a predefined allowed set. + - Delimiter is treated as a reserved hierarchy marker in nested-aware flows. + - Behavior difference for new object creation: + - Iceberg nested schema creation that uses delimiter as hierarchy path is allowed. + - Hive creation of a non-nested schema name that contains the configured delimiter is rejected + with validation error. +- **Option 2 (unrestricted delimiter)**: + - Server allows any delimiter value configured by users. + - Compatibility is prioritized for engines that treat schema name as plain string. + - Behavior difference for new object creation: + - Hive can create a non-nested schema successfully even when the schema name contains the + configured delimiter. + - Nested interpretation is applied only in nested-aware request paths (for example Iceberg + namespace APIs), not as a blanket rule for all engines. + +### Delimiter Validation and Rejection Rationale + +Delimiter validity should be explicit and observable, not implicit. + +- Validation checkpoints: + - Validate delimiter when server starts or when delimiter configuration is updated. + - Re-validate against existing catalog schema names before enabling nested mode for a catalog. + - Reject invalid delimiter configuration early before request-time namespace operations. +- Validation rules: + - Delimiter must be a single non-empty character. + - Delimiter must not be `.` because `.` is reserved as physical storage separator. + - Delimiter should avoid characters that cause parser or route ambiguity in REST/SQL contexts + (for example `/`). + - Under Option 1, delimiter must belong to server predefined allowlist. + - Under Option 2, delimiter is user-defined but still must pass safety checks above. +- Rejection rationale (why some delimiters are not permitted): + - Avoid hierarchical parsing ambiguity and inconsistent split/join behavior. + - Preserve compatibility with existing schema/table identifier parsing across engines. + - Prevent migration risk where existing names collide with hierarchy semantics. + - Keep cross-engine behavior predictable when Iceberg and Hive treat schema names differently. +- Error reporting requirements: + - Return actionable validation error containing rejected delimiter, rejection reason, and + suggested alternatives. + - Example: "Delimiter '/' is not allowed because it conflicts with path parsing. Try ':', ';', + or '$'." + + +### Parsing Sequence Diagram + +```mermaid +sequenceDiagram + participant Client as Client/Connector + participant Config as Connector Config + participant API as Gravitino REST API + participant Mapper as HierarchicalSchema Mapper + participant Store as EntityStore + + Client->>Config: Load namespace separator + Config-->>Client: separator (for example ':') + Client->>API: GET /schemas?parentSchema=A:B + API->>Mapper: Parse parentSchema by separator ':' + Mapper->>Store: list all schemas + Store-->>Mapper: all schemas + Mapper->>Mapper: filter direct children under A:B + Mapper-->>API: hierarchy-aware result + API-->>Client: response (Iceberg-compatible namespace view) +``` + + +### Iceberg REST Side Behavior + +- **Create nested namespace**: + - Creating `A:B:C` creates (or ensures existence of) `A`, `A.B`, and `A.B.C` in one atomic + operation. + - Parent-chain creation is transactional: if any step fails, all created parents in this request + are rolled back and no partial parent namespaces remain. + - Owner assignment rule for auto-created parents: + - If a parent is newly auto-created, owner must be the same as the owner assigned to the final + target namespace in the same create request. + - The full auto-created parent chain and the final target namespace must share a consistent owner + value for that operation. +- **Update nested namespace**: + - Support updating namespace properties through mapped schema operations. + - Property update is applied to the mapped target namespace scope. +- **Drop nested namespace**: + - Iceberg REST side does not support cascade delete for namespace. + - If cascade parameter is provided, return unsupported-parameter error directly. + - Drop must fail when target namespace still contains child namespaces, tables, or views. + - Users must delete children objects explicitly before dropping parent namespace. +- **Rename nested namespace**: not needed because Iceberg REST does not support namespace rename. + +### Gravitino Side Behavior + +- `list schema` should express nested hierarchy semantics for users. +- `list schema` REST API (GET `/metalakes/{metalake}/catalogs/{catalog}/schemas`) should support an + optional query parameter `parentSchema`. + - When `parentSchema` is absent, return top-level schemas only (first layer). + - When `parentSchema` is provided, return only the + direct child schemas under the + given parent (next layer), instead of the full subtree. + - `parentSchema` value follows direct `HierarchicalSchema` path format with configured separator + (for example `A:B` when separator is `:`). +- Gravitino does not provide a dedicated `list sub-schema` API; hierarchy is expressed via + `list schema`/`list namespaces` results. +- Example: for schemas `A`, `B`, `A:B`, `A:B:C`, hierarchy view is `A -> A:B -> A:B:C` and `B`; + root listing returns `A` and `B`, and querying parent `A` returns `A:B`. +- To make nested semantics explicit, `list namespaces` should express parent-child relationships + (hierarchical view) even when underlying storage is flat. +- Example hierarchical view from flat schemas: `A` -> `A:B` -> `A:B:C`, and `B` as another root. +- This list-level hierarchical expression is the primary semantic model for users, reducing + ambiguity caused by one request creating multiple physical schema objects. +- Gravitino server REST supports namespace create/update/drop operations for nested namespace + workflows, aligned with Iceberg REST behavior. +- Existing schema/table APIs remain compatible with non-nested cases. + +Examples (Gravitino REST side): + +- **Create from Gravitino side** + - Request: `POST /metalakes/m1/catalogs/c1/schemas` with `name=A:B:C` + - Behavior: ensure parent chain exists (`A`, `A:B`) and then create `A:B:C`. +- **List from Gravitino side** + - Request: `GET /metalakes/m1/catalogs/c1/schemas` + - Behavior: return top-level schemas only (first layer), for example `A`, `B`. + - Request: `GET /metalakes/m1/catalogs/c1/schemas?parentSchema=A:B` + - Behavior: return direct children of `A:B` only (next layer), for example `A:B:C`, `A:B:D`. +- **Alter from Gravitino side** + - Request: `PUT /metalakes/m1/catalogs/c1/schemas/A:B:C` with updates + (for example set/remove properties). + - Behavior: update properties on target schema `A:B:C` only; parent scopes are not modified. +- **Delete from Gravitino side** + - Request: `DELETE /metalakes/m1/catalogs/c1/schemas/A:B` + - Behavior: fail if `A:B` still contains child namespace/table. + - Behavior: no cascade mode; children must be removed first, then delete `A:B`. + - Request with cascade parameter (for example `?cascade=true`): reject with unsupported-parameter + error. + +## Privileges and Authorization + +- Authorization follows nested namespace scope by logical `HierarchicalSchema` path and mapped schema name. +- Namespace privileges follow inheritance: privilege on parent namespace applies to child namespace. +- For operations requiring `USE_SCHEMA`, authorization succeeds if any ancestor scope + (including the current schema scope) has `USE_SCHEMA`; it is not required on every level. +- Effective rule for `A:B:C`: check `A:B:C` -> `A:B` -> `A`, and pass on the first scope that has + `USE_SCHEMA`. +- Parent-chain walking overhead is mitigated by existing `EntityStore` cache behavior; no additional + authorization-layer cache is introduced in this phase. +- UI privilege granting is one usage scenario of this overall nested namespace solution. +- To prevent privilege escalation, auto-creating missing parent namespaces requires one of: + - requester has `create_schema` on each missing parent scope, or + - requester has dedicated admin capability for bootstrap parent creation. +- If neither condition is met, create `A:B:C` must fail instead of implicitly creating unauthorized + parent scopes. + +### Client API Surface (Java/Python) + +- Java client: + - Keep existing string-based methods for compatibility. + - Only add `listSchemas(parentSchema)` support so callers can request direct children under a + specific parent namespace. + - For create/update/drop and other schema operations, continue using existing string-based schema + name parameters; users compose hierarchical schema names themselves (for example `A:B:C`). + - No new typed path wrapper (`SchemaPath`) or segment-based overloads are introduced in this + phase. + +Simple Java client examples: + +- `listSchemas()` -> returns top-level schemas, for example `A`, `B`. +- `listSchemas("A:B")` -> returns direct children, for example `A:B:C`, `A:B:D`. +- `createSchema("A:B:C", ...)` -> users pass composed schema name directly. + +### Option P1 (Recommended): Extend `create_schema` semantics + +- Keep current privilege model and do not add a new privilege type. +- Clarify `create_schema` as container-scoped capability: permission on parent namespace allows + creating direct child namespace under that scope. +- Example: `create_schema` on `A` allows creating `A:B`, and `create_schema` on `A:B` allows + creating `A:B:C`. + +Pros: + +- Lowest implementation and migration cost. +- Reuses existing authorization model and UI privilege workflow. +- Keeps backward compatibility for current grants. + +Cons: + +- Semantics are less explicit because `create_schema` now covers both normal schema creation and + nested namespace creation. + +### Option P2: Introduce a dedicated nested-namespace privilege + +- Add a new privilege (for example `create_nested_namespace`) for creating child namespaces. +- Keep `create_schema` semantics unchanged for existing schema creation behavior. +- Evaluate both privileges independently in authorization expression where needed. + +Pros: + +- Clearer and more explicit permission model. +- Better long-term extensibility for fine-grained namespace governance. + +Cons: + +- Requires privilege model/API/UI updates and migration planning. +- Increases operational complexity for users and administrators. + +### Selection Guidance + +- Phase-1 recommends Option P1 for faster delivery and lower risk. +- Option P2 can be considered in a later phase if stronger permission separation is required. + +Examples: + +- Privilege on `A:B` applies to that specific scope. +- Privilege on `A` also applies to `A:B` (or other configured child path) based on the namespace inheritance rule. + +## Code Snippets (Design-Level) + +The following snippets are design-level examples to clarify how `HierarchicalSchema` +(`:` preferred) should be converted and consumed in key code paths. + +### Snippet 1: Convert Iceberg namespace to logical path and physical schema + +```java +// Example utility methods in IcebergRESTUtils (or a dedicated HierarchicalSchemaUtil) +public static String serializeHierarchicalPath(String[] levels) { + // ["team", "sales"] -> "team:sales" + // logical separator is configurable and not allowed inside one level. + return String.join(configuredSeparator, levels); +} + +public static String[] parseHierarchicalPath(String path) { + // "team:sales" -> ["team", "sales"] + return path.split(Pattern.quote(configuredSeparator), -1); +} + +public static String toPhysicalSchemaName(String hierarchicalPath) { + // Reversible mapping: encode each segment before join. + // Example: ["my.schema", "sales"] -> "my%2Eschema.sales" + return encodeAndJoinSegments(parseHierarchicalPath(hierarchicalPath)); +} +``` + +### Snippet 2: Namespace extraction in authorization interceptor + +```java +// Example in IcebergMetadataAuthorizationMethodInterceptor +Namespace rawNamespace = RESTUtil.decodeNamespace(value); +String hierarchicalPath = HierarchicalSchemaUtil.toPath(rawNamespace, ":"); +String schema = HierarchicalSchemaUtil.toPhysicalSchemaName(hierarchicalPath); + +nameIdentifierMap.put( + Entity.EntityType.SCHEMA, + NameIdentifierUtil.ofSchema(metalakeName, catalog, schema)); +``` + +### Snippet 3: Parent-scope authorization check + +```java +// Example path inheritance for A:B:C +List<String> authzScopes = HierarchicalSchemaUtil.parentScopes("A:B:C"); +// Result: ["A", "A:B", "A:B:C"] +// Authorization passes if user has required privilege on any allowed parent scope by policy. +``` + +### Snippet 4: Create nested namespace in executor flow + +```java +// For create namespace A:B:C, ensure parent schemas exist in physical model +for (String scope : HierarchicalSchemaUtil.parentScopes("A:B:C")) { + String schemaName = HierarchicalSchemaUtil.toPhysicalSchemaName(scope); // A, A.B, A.B.C + // create schema if not exists +} +``` + +## Affected Classes + +### Iceberg REST and namespace dispatch + +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/iceberg/service/IcebergRESTUtils.java` +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/iceberg/service/dispatcher/IcebergNamespaceOperationDispatcher.java` +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/iceberg/service/dispatcher/IcebergNamespaceOperationExecutor.java` +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/iceberg/service/dispatcher/IcebergNamespaceEventDispatcher.java` + +### Authorization interception + +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/server/web/filter/BaseMetadataAuthorizationMethodInterceptor.java` +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/server/web/filter/IcebergMetadataAuthorizationMethodInterceptor.java` +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/server/web/filter/LoadTableAuthzHandler.java` +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/server/web/filter/RenameTableAuthzHandler.java` +- `iceberg/iceberg-rest-server/src/main/java/org/apache/gravitino/server/web/filter/RenameViewAuthzHandler.java` + +### Identifier and metadata object mapping + +- `api/src/main/java/org/apache/gravitino/NameIdentifier.java` +- `core/src/main/java/org/apache/gravitino/utils/NameIdentifierUtil.java` + +### Tests + +- `iceberg/iceberg-rest-server/src/test/java/org/apache/gravitino/server/web/filter/TestIcebergMetadataAuthorizationMethodInterceptor.java` +- `api/src/test/java/org/apache/gravitino/TestNameIdentifier.java` +- `core/src/test/java/org/apache/gravitino/utils/TestNameIdentifierUtil.java` + +## Expected Changes + +### 1) Namespace path mapping + +- Add a dedicated conversion utility for `HierarchicalSchema` path: + - Iceberg namespace levels -> logical path (preferred `:`). + - Logical path -> physical schema name (phase-1 uses `.` flattened mapping). +- Override `Capability.specificationOnName(SCHEMA, name)` naming rules for related catalogs so + schema names containing `:` are accepted in this phase. + +### 2) Authorization behavior + +- In interceptor and handlers, stop treating the last namespace level as the only schema segment. +- Build schema identity from the full namespace path through conversion rules. +- Evaluate parent-scope inheritance using hierarchical logical scopes (`A`, `A:B`, `A:B:C`) before or during expression evaluation. +- For `USE_SCHEMA` checks, short-circuit on the nearest scope that has permission; do not require + `USE_SCHEMA` on each intermediate level. + +### 3) Namespace operation behavior + +- `createNamespace` should ensure parent schemas exist for each hierarchical level. +- Parent-chain creation must be atomic as one transaction; failures must not leave partial parents. +- `updateNamespace` should support property updates for mapped namespace scope. +- `dropNamespace` should target mapped physical schema and preserve existing non-nested behavior. +- `listSchemas` should accept optional query parameter `parentSchema`. + - Absent `parentSchema`: return top-level schemas only. + - Present `parentSchema`: return direct children only. +- `listNamespaces` should return hierarchy-aware semantics (or equivalent parent-child expression) + while keeping current flat storage model. +- Catalog implementations must support namespace lifecycle APIs (create/list/alter/drop namespace) + for this feature path. + +### 4) Identifier compatibility + +- Keep `NameIdentifier` external compatibility for existing dotted identifiers. +- Add schema-level rendering/parsing guidance for logical separator and quoted schema output where ambiguity exists. +- Keep change scope limited to schema handling in this phase to reduce regression risk for table/view/function paths. + +## Compatibility + +- No metadata model migration required. +- Existing non-nested namespace behavior remains unchanged. +- Limiting quoted identifier parsing to `schema` reduces regression risk for catalog/table/view/function identifier parsing. +- Internal representation in Gravitino may use `:` for hierarchical schema semantics. +- Spark/Flink/Trino connector-facing namespace representation must stay consistent with Iceberg + conventions and should not require users to input Gravitino-internal `:` format directly. +- Connector layer is responsible for translation between Iceberg-style namespace representation and + Gravitino internal hierarchical schema representation. +- Connector changes are mandatory in Spark/Flink/Trino integration layers; this is not a pure + server-only change. +- Upgrade guard: + - validate selected logical separator against existing schema names before enabling nested mode. + - if conflict exists, users can pick another logical separator or rename conflicting schemas. + +Rationale: + +- Keep connector-facing behavior aligned with Iceberg to preserve existing engine user experience + and avoid introducing a Gravitino-specific namespace syntax into Spark/Flink/Trino SQL or APIs. +- Reduce migration cost and compatibility risk for current Iceberg workloads, scripts, and + operational tooling that already assume Iceberg namespace conventions. +- Isolate internal representation changes inside Gravitino/connector translation boundaries, so + future internal evolution does not force external breaking changes for engine integrations. + +Engine Delimiter Support (Connector-facing): + +| Engine | User-facing namespace delimiter | Requires internal `:` input? | Notes | +|---|---|---|---| +| Spark connector | `a.b.c` style namespace string | No | Spark side uses dotted namespace representation and connector converts to internal format. | +| Flink connector | `a.b.c` style namespace string | No | Flink side uses dotted namespace representation and connector converts to internal format. | +| Trino connector | `"a.b.c"` style quoted namespace string | No | Trino side uses quoted dotted namespace representation and connector converts to internal format. | + +All engines should keep external namespace semantics aligned with Iceberg. Internal `:` is an +implementation detail inside Gravitino and connector translation logic. + +### Connector `NestedNameIdentifier` Conversion + +Connector side must explicitly convert namespace representation when building and parsing +`NestedNameIdentifier`/`NameIdentifier` values: + +- **Input parsing (engine -> connector)**: + - Read namespace in engine-native/Iceberg style. + - Build connector logical path first, then convert to Gravitino internal schema representation. +- **Request construction (connector -> Gravitino)**: + - For schema-level operations, send converted schema name in request/path/query expected by + Gravitino REST. + - For list operations, `parentSchema` must use the converted internal hierarchical schema + representation. +- **Response rendering (Gravitino -> connector -> engine)**: + - Convert internal hierarchical schema representation back to engine-native/Iceberg style before + returning identifiers to Spark/Flink/Trino users. +- **Round-trip requirement**: + - `engine identifier -> connector converted identifier -> server -> connector rendered identifier` + must be stable and lossless for nested namespace paths. + +Example conversion flow: + +- Engine input: namespace `[A, B, C]`, table `t1` +- Connector logical identifier: `A.B.C.t1` (engine-facing) +- Connector to Gravitino identifier: schema `A:B:C`, table `t1` +- Gravitino response schema: `A:B:C` +- Connector rendered back to engine: namespace `[A, B, C]`, table `t1` + +Trino-specific example: + +- Trino input namespace string: `"a.b.c"` +- Connector converts to Gravitino internal schema: `a:b:c` +- Gravitino returns schema: `a:b:c` +- Connector renders back to Trino quoted style: `"a.b.c"` Review Comment: Add a chapter to list all the planned works of this features. -- This is an automated message from the Apache Git Service. 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