Skip empty ordering scans for a scoped numeric query

[stopachka]

An allowlisted numeric query can scan the full ordering index when its filter has no matches. Add a one-row existence probe inside the same SQL statement so that PostgreSQL can skip that empty join. The original joins, result envelope and pagination remain in place; nonempty requests continue through the original plan.

The override requires the exact app and complete normalized query shape plus the measured schema, scan choices and SQL layout. Existing hint-disable controls bypass it. The precheck copies the filter predicates, so correctness does not depend on cached cardinality metadata remaining current until execution.

Validation:

• Eight tests and 86 assertions pass, including complete-result/page comparisons, null/missing values, ties, scope and hint switches, and a stale-schema regression.
• Final-code synthetic benchmark with 20,000 entities and verified applied hints: empty range 27.85ms→0.06ms; shared-buffer hits 101,432→3, with the original scans never executed.
• Nonempty bounds retain the original scans and add four buffer hits; no measured slowdown across the tested cases. These are local measurements, not production savings.
• Independent review, clj-kondo and git diff --check pass.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

Review profile: CHILL

Plan: Advanced

Run ID: c1095bee-d280-41dd-8762-1529a87e0e68

📥 Commits

Reviewing files that changed from the base of the PR and between cddd016 and fe4a857.

📒 Files selected for processing (2)

• server/src/instant/db/scoped_query_plans.clj
• server/test/instant/db/numeric_range_plan_test.clj

Included review availability: Your plan provides up to 10 included reviews per hour; 7 remain after this review.

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📝 Walkthrough

Walkthrough

The query planner adds a guarded upper-bound rewrite for a specific timestamp query shape. Tests verify the generated CTE and hints, rewrite gates, feature flags, and equivalence of paged results.

Changes

Numeric upper-bound planning

Layer / File(s)	Summary
Upper-bound plan rewrite server/src/instant/db/scoped_query_plans.clj	Adds numeric-upper-bound, which validates the measured query shape and adds an upper-bound CTE, an :exists predicate, and an index-scan hint. apply-plan tries this rewrite after numeric-range.
Rewrite validation and result checks server/test/instant/db/numeric_range_plan_test.clj	Adds the upper-bound query fixture and tests for plan structure, exact matching conditions, hint switches, query-hash flags, schema changes, boundary values, ties, and paged-result equality.

Priority: ⬇️ Low

Estimated code review effort: 3 (Moderate) | ~30 minutes

Change: Refactor

Sequence Diagram(s)

sequenceDiagram
  participant QueryCompiler
  participant apply-plan
  participant numeric-upper-bound
  participant PostgreSQL
  QueryCompiler->>apply-plan: compile timestamp upper-bound query
  apply-plan->>numeric-upper-bound: validate query and scan layout
  numeric-upper-bound-->>apply-plan: return upper-bound CTE and exists predicate
  apply-plan-->>QueryCompiler: return rewritten query plan
  QueryCompiler->>PostgreSQL: execute rewritten SQL
  PostgreSQL-->>QueryCompiler: return paged results

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Merge Risk: ⚪ Minimal · up to fe4a8

The narrowly scoped query optimization retains equivalent paged results in the covered cases and respects existing hint-disable controls. No actionable merge risk remains.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: skipping empty ordering scans for scoped numeric queries.
Description check	✅ Passed	The description directly explains the existence-probe optimization, its scope, safeguards, unchanged behavior, and validation results.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check. Docstring coverage is scoped to functions touched by this diff. Analyzed 0 functions across 0…
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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