feat(cubesql): Support FULL and RIGHT joins with non-push-to-Cube SQL push down

[MazterQyou]

Check List

• Tests have been run in packages where changes have been made if available
• Linter has been run for changed code
• Tests for the changes have been added if not covered yet
• Docs have been added / updated if required

Description of Changes Made

This PR fixes a regression introduced by grouped joins with SQL push down (#10234): a FULL OUTER JOIN of two grouped subqueries (e.g. period-over-period cost comparison) now fails with Unsupported join type for join subquery: Full. The rewrite already produced the correct plan; only SQL generation and the join-type templates were limited to Inner/Left.

This adds FULL and RIGHT support for the non-push-to-Cube path (both sides as standalone subqueries, where outer-join semantics map cleanly to SQL). The push-to-Cube path — where the join is folded inside the Cube query with
its own grouping/measures — explicitly keeps refusing FULL/RIGHT, since NULL-extended outer rows there are not validated.

Push down is template-gated: FULL/RIGHT only push down when the target data source declares the join_types/* template, otherwise the join falls back to DataFusion.

[claude]

Claude finished @MazterQyou's task in 2m 16s —— View job

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Code Review

Verdict: Looks good overall — clean, well-scoped fix. 0 high, 0 medium, 3 low (all suggestions / nits posted inline).

Full review (expand)

Summary

The fix is well-scoped: the rewrite already produced a correct plan for FULL/RIGHT joins of two grouped subqueries; the PR just wires SQL generation and join-type templates through. Separation between the push-to-Cube path (refuses FULL/RIGHT) and the non-push-to-Cube path (now supports them) is clearly commented and consistently enforced.

What's good

• Template-gating via is_subquery_join_type_supported (join.rs:996) is the right abstraction — it composes the join-type rule with can_rewrite_template, so non-supporting drivers fall back to DataFusion rather than emitting unsupported SQL.
• push_to_cube parameter correctly differentiates the two paths: hardcoded true for transform_ungrouped_join_grouped (always refuses FULL/RIGHT), left_push_to_cube.0 for transform_grouped_join_grouped (refuses FULL/RIGHT only when folding into Cube query).
• continue vs return false in the grouped-grouped variant (join.rs:1320) is the right choice — lets the non-push variant of the eclass still match.
• Driver-specific opt-outs (CubeStoreQuery.ts, MysqlQuery.ts) are well-commented with the underlying reason.
• Comments at wrapper.rs:3462 and :3600 preserve the invariant for future maintainers.

Findings (all low)

1. BaseQuery.js — making right/full the default exposes all non-overriding drivers; verify each one. Snowflake's explicit templates.join_types.full = 'FULL' (SnowflakeQuery.ts:122) is now redundant. Inline comment posted.
2. Test coverage — only FULL is exercised; RIGHT is not, and there's no negative test for the template-gating fallback or for the push-to-Cube path still rejecting FULL/RIGHT. Inline comment posted.
3. Minor redundancy in transform_ungrouped_join_grouped — the data-source lookup runs even though push_to_cube=true makes Right/Full unreachable. Functionally correct but slightly misleading. Inline comment posted.

Security / performance

• No new user-input surfaces; the templates are static strings. No injection vector introduced.
• No allocation/hot-path concerns: the rewrite-rule helper does one extra MetaContext clone per rule construction (cheap, one-time at setup) and one template lookup per match attempt (already done for other gates).

Checklist

• Reviewed Rust changes (join.rs, wrapper.rs, service.rs, tests)
• Reviewed JS/TS adapter changes (BaseQuery.js, CubeStoreQuery.ts, MysqlQuery.ts)
• Posted 3 inline findings
• Verified push-to-Cube path still rejects FULL/RIGHT (both code paths in generate_sql_for_push_to_cube)

• [Branch](https://github.com/cube-js/cube/tree/cubesql/grouped-join-grouped-right-full)

[codecov]

Codecov Report

❌ Patch coverage is 96.37306% with 7 lines in your changes missing coverage. Please review.
✅ Project coverage is 83.37%. Comparing base (38b7d8c) to head (37109d0).

Files with missing lines	Patch %	Lines
.../cubesql/src/compile/rewrite/rules/wrapper/join.rs	90.90%	4 Missing ⚠️
...t/cubesql/cubesql/src/compile/test/test_wrapper.rs	97.79%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #11008      +/-   ##
==========================================
+ Coverage   78.82%   83.37%   +4.55%     
==========================================
  Files         471      255     -216     
  Lines       94412    77447   -16965     
  Branches     3494        0    -3494     
==========================================
- Hits        74417    64569    -9848     
+ Misses      19486    12878    -6608     
+ Partials      509        0     -509     

Flag	Coverage Δ
cube-backend	?
cubesql	83.37% <96.37%> (+0.04%)	⬆️

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[claude]

Claude finished @MazterQyou's task in 1m 6s —— View job

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Code Review

Re-checked after PR synchronize: no new commits since the prior review (still 37109d0). All 3 prior inline findings remain unresolved and still applicable to the current diff — re-affirming them rather than re-posting.

Verdict: Looks good overall — clean, well-scoped fix. 0 high, 0 medium, 3 low (suggestions only; all already inline on the PR).

Prior findings (still apply)

1. rust/cubesql/cubesql/src/compile/rewrite/rules/wrapper/join.rs:1068 — push_to_cube=true in transform_ungrouped_join_grouped makes the template lookup unreachable for Right/Full; consider a clarifying comment or inline match guard.
2. rust/cubesql/cubesql/src/compile/test/test_wrapper.rs:1249 — coverage gap: RIGHT JOIN isn't asserted, no negative test for template-gating fallback, no test that push-to-Cube path still rejects FULL/RIGHT.
3. packages/cubejs-schema-compiler/src/adapter/BaseQuery.js:4608 — making FULL/RIGHT base-default exposes every non-overriding driver; double-check exotic adapters (Druid, Pinot, Elasticsearch SQL, Materialize, MongoDB). Snowflake's templates.join_types.full = 'FULL' is now redundant.

No new high/medium issues introduced. Security and performance unchanged from prior pass.

• [Branch](https://github.com/cube-js/cube/tree/cubesql/grouped-join-grouped-right-full)