Fix nested relation paths generating invalid SQL multi-level dot notation

[Copilot]

SQL only supports two-level dot notation ("table"."column"). Paths like projects.user.name were generating "projects"."user"."name" — invalid in every SQL dialect. The correct output is "user"."name", using the leaf relation segment as the joined table alias.

Changes

interpreter.ts — field() method

• Applies a second lastIndexOf on the relation path to extract only the leaf alias ('user' from 'projects.user')
• Passes the leaf alias to joinRelation(alias, context) — ORM implementations are responsible for resolving the full join chain
• Tracks only the alias in _joins
• _foreignField() reverted to simple two-part escaping: "alias"."column"
• usingFieldPrefix() keeps prefix accumulation so nested elemMatch correctly builds the full path before alias extraction

// Before (invalid SQL):
new Field('eq', 'projects.user.name', 'test')
// → "projects"."user"."name" = $1  ❌

// After (valid SQL):
// → "user"."name" = $1  ✅
// joinRelation called with: 'user'

Works for both direct field notation (projects.user.name) and nested elemMatch:

elemMatch('address', elemMatch('city', eq('name', 'NYC')))
// prefix accumulates: 'address.city.' → field 'name' → alias 'city'
// → "city"."name" = $1  ✅

interpreters.spec.ts

• Corrected 3 tests from the previous session that asserted invalid multi-level SQL output
• Added describe('auto join nested relations') block covering direct nested field notation, consistent with PR feat: support deeply nested field path #55

Original prompt

Start implementation

[Chronological Review: The conversation began with the user requesting to find potential issues in the file `interpreter.ts`, particularly related to joining nested relations. The user then shifted to requesting the start of the implementation phase, indicating a transition from analysis to action.]

[Intent Mapping:

1. "find potential issues, especially related to joining nested relations and suggest a fix" - The user is looking for specific problems in the code that could affect functionality.
2. "Start implementation" - The user is ready to move forward with coding after identifying issues.]

[Technical Inventory:

• File: /Users/sergiistotskyi/projects/ucast/packages/sql/src/interpreter.ts - This file is central to the user's current work, likely containing logic for SQL interpretation and execution.
• Concepts: Nested relations and SQL joins are critical to the user's focus, indicating a need for robust handling of complex data structures.]

[Code Archaeology: No specific code changes or functions were discussed in detail yet, but the focus is on identifying issues in the existing code.]

[Progress Assessment: The user has identified a need for issue discovery and is transitioning to implementation. No specific tasks have been completed yet, but the groundwork for understanding the code is being laid.]

[Context Validation: The user is working on the interpreter.ts file and is focused on ensuring that nested relations are handled correctly in SQL operations.]

[Recent Commands Analysis:

• Last Agent Commands: The user requested to find potential issues and then to start implementation.
• Tool Results Summary: No specific tool results were generated as the conversation was primarily focused on user requests.
• Pre-Summary State: The agent was actively discussing potential issues in the interpreter.ts file related to nested relations when the token budget was exceeded.
• Operation Context: The commands were executed to address the user's goal of improving the SQL interpreter's handling of complex data structures.]

1. Conversation Overview: - Primary Objectives: - "find potential issues, especially related to joining nested relations and suggest a fix" - "Start implementation" - Session Context: The user is focused on the `interpreter.ts` file, seeking to identify and resolve issues related to SQL joins and nested relations before proceeding with implementation. - User Intent Evolution: The user initially sought to identify issues but quickly moved to the implementation phase, indicating readiness to act on findings.

2. Technical Foundation:

• File: /Users/sergiistotskyi/projects/ucast/packages/sql/src/interpreter.ts
• Purpose: This file is crucial for SQL interpretation and execution, particularly in handling nested relations.
• Current State: The user is in the process of identifying issues before starting implementation.

3. Codebase Status:

• File Name: interpreter.ts
• Purpose: Contains logic for SQL interpretation, particularly for handling nested relations.
• Current State: No specific modifications have been made yet, but the user is preparing to implement fixes.
• Key Code Segments: Not yet discussed in detail.
• Dependencies: Relates to SQL execution and data handling.

4. Problem Resolution:

• Issues Encountered: Potential issues with joining nested relations.
• Solutions Implemented: None yet, as the user is still in the analysis phase.
• Debugging Context: Ongoing identification of issues before implementation.
• Lessons Learned: Understanding of nested relations is critical for SQL operations.

5. Progress Tracking:

• Completed Tasks: None yet; the user is still in the analysis phase.
• Partially Complete Work: Identifying issues related to nested relations.
• Validated Outcomes: None yet.

6. Active Work State:

• Current Focus: Identifying issues in interpreter.ts related to nested relations.
• Recent Context: The user has requested to find potential issues and then to start implementation.
• Working Code: No specific code snippets have been discussed yet.
• Immediate Context: The user is preparing to address issues in the SQL interpreter.

7. Recent Operations:

• Last Agent Commands:
  • "find potential issues, especially related to joining nested relations and suggest a fix"
  • "Start implementation"
• Tool Results Summary: No specific tool results were generated; the focus was on user requests.
• Pre-Summary State: The agent was discussing potential issues in interpreter.ts when the token budget was exceeded.
• Operation Context: The commands were executed to align with the user's goal of improving the SQL interpreter's handling of nested relations.

8. Continuation Plan:

• [Pending Task 1]: Identify specific issues in interpreter.ts related to nested relations and suggest fixes.
• [Pending Task 2]: Begin implementation of identified fixes once issues are clarified.
• [Priority Information]: Addressing ...

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.06%. Comparing base (8c518ea) to head (2ed2f3a).
⚠️ Report is 4 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master      #71      +/-   ##
==========================================
+ Coverage   91.93%   92.06%   +0.12%     
==========================================
  Files          12       12              
  Lines         248      252       +4     
  Branches       40       41       +1     
==========================================
+ Hits          228      232       +4     
  Misses         12       12              
  Partials        8        8              

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