fix(wren-core): preserve composite-key predicates in relationship joins

[goldmedal]

Summary

• RelationChain::plan extracted all identifiers from a relationship condition and then used only the first two — so a.x = b.x AND a.y = b.y lost the second equality, breaking composite-key joins. The TPCH partsupp fixture in this repo already carries a TODO noting the gap (// ps_partkey and ps_suppkey should be composite primary key).
• Add collect_join_keys (new helper in mdl/utils.rs) that parses the condition expression and returns equality pairs in AST order, rejecting non-equality / disjunction / non-column shapes with a clear error.
• relation_chain.rs now rebases each column to the right alias (same logic as before) and ANDs the per-pair equalities into the final join predicate.
• This is the Phase 1 prerequisite for declarative composite primary keys (separate follow-up); on its own it already unlocks composite-join condition strings, which were previously expressible in MDL but silently truncated.

Test plan

• cargo fmt --all
• cargo clippy --all-targets --all-features -- -D warnings
• RUST_MIN_STACK=8388608 cargo test --lib --tests --bins --release — 133 passed (8 new helper tests + 1 new e2e composite-key test)
• sqllogictest suites (view.slt, model.slt, tpch/tpch.slt, type.slt) all pass

🤖 Generated with Claude Code

Summary by CodeRabbit

• New Features

  • Support composite relationship keys: joins can be defined by multiple column equalities.

• Bug Fixes

  • Preserve multi-column join predicates during SQL transformation so all key equalities are included.

• Tests

  • Added unit and integration tests validating single- and multi-key join conditions, error cases, and snapshot coverage.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Pro

Run ID: b5ecb6ba-b95e-4308-ab50-935890f38e9e

📥 Commits

Reviewing files that changed from the base of the PR and between 1cba5ef and 05febe4.

📒 Files selected for processing (1)

• core/wren-core/core/src/mdl/mod.rs

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Walkthrough

Parses SQL join condition strings into ordered column-equality pairs, updates relation chain logic to rebase and AND-conjoin all equality predicates for composite-key relationships, and adds an end-to-end test validating composite join predicates appear in generated SQL.

Changes

Composite Key Join Condition Support

Layer / File(s)	Summary
Join key extraction utilities core/wren-core/core/src/mdl/utils.rs	New public function collect_join_keys parses SQL join condition strings into DataFusion expressions, recursively extracts ordered column pairs from AND-conjoined equality predicates, and rejects non-equality operators, disjunctions, and non-column operands. Unit tests validate single-key, composite/multi-key, parenthesized, and quoted-identifier extraction plus error handling for > operators, OR disjunctions, and literal operands.
Relation chain join predicate construction core/wren-core/core/src/logical_plan/analyze/relation_chain.rs	Updated imports to use collect_join_keys and DataFusionError. Join predicate logic now parses relationship conditions into key pairs, rebases each pair to the correct table alias, and combines all equalities with AND conjunctions, replacing the previous single-equality assumption.
Composite-key relationship integration test core/wren-core/core/src/mdl/mod.rs	New async test test_composite_key_relationship builds a manifest with a composite-key relationship between partsupp and part, runs the SQL transformation for a calculated field, and snapshot-tests that both equality predicates appear in the generated ON clause conjoined with AND.

🎯 3 (Moderate) | ⏱️ ~20 minutes

🐰 I nibble through predicates bright,
Equalities pair up, snug and tight,
AND by AND the join lines sing,
Composite keys make my heart spring! 🌿

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title 'fix(wren-core): preserve composite-key predicates in relationship joins' directly and clearly describes the main change: fixing how relationship joins handle composite-key predicates by preserving all equality conditions instead of truncating them.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch worktree-plan-0525-115336

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