refactor(dns): remove the unused instance-DNS view and its SQL hostname function

[chet]

Summary

nico_inet_to_dns_hostname (a PL/pgSQL function) and the dns_records_instance view derived forward A/AAAA names directly from instance IP addresses (10.1.2.3 → 10-1-2-3). The view was dropped from the served dns_records view in early 2025 and hasn't been served since — repo-wide, the only thing touching either object was a unit test. IP-derived hostnames are produced by the host-naming strategy (the Rust address_to_hostname helper) and stored in machine_interfaces.hostname, which the shortname/adm views serve, so the SQL function was a stale duplicate of that logic.

• Migration drops dns_records_instance, then nico_inet_to_dns_hostname(inet).
• Removes the two tests that exercised them.

Verified no remaining consumers: nothing in code or config queries them (PowerDNS uses the remote backend → the combined dns_records view, which excludes instance), no external grants on the view, and a RESTRICT DROP of both succeeds cleanly against the schema. IP-derived DNS is unchanged — it flows through the naming strategy + the stored hostname, not this view.

Implements #2709. Follow-up to the #2630 reverse-DNS epic.

Draft pending review.

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📥 Commits

Reviewing files that changed from the base of the PR and between f947966 and 894641f.

📒 Files selected for processing (2)

• crates/api-db/migrations/20260622072105_remove_unused_instance_dns_view.sql
• crates/api-db/src/dns/mod.rs

💤 Files with no reviewable changes (1)

• crates/api-db/src/dns/mod.rs

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Summary by CodeRabbit

• Chores
  • Removed unused database objects and their corresponding tests. This maintenance activity eliminates redundant components, reduces technical debt, optimizes the database schema, and improves overall system organization. The internal cleanup enhancements focus on code quality and long-term maintainability without any impact on user-facing features or existing functionality.

Walkthrough

A database migration drops the dns_records_instance SQL view and nico_inet_to_dns_hostname(inet) function using IF EXISTS guards, as equivalent hostname derivation now occurs in Rust. Two integration tests validating those removed database objects, along with their associated test-support imports, are deleted from the DNS module.

Changes

DNS SQL Object Removal and Test Cleanup

Layer / File(s)	Summary
Drop dns_records_instance view and nico_inet_to_dns_hostname function crates/api-db/migrations/20260622072105_remove_unused_instance_dns_view.sql	Migration issues DROP VIEW IF EXISTS dns_records_instance and DROP FUNCTION IF EXISTS nico_inet_to_dns_hostname(inet) to remove stale database objects whose logic has been superseded in Rust.
Remove integration tests for dropped SQL objects crates/api-db/src/dns/mod.rs	Removes the carbide_test_support, Case/check_cases_async, and sqlx::Row test imports, along with two #[crate::sqlx_test] async tests that validated IPv6 hostname expansion and dns_records_instance qname resolution against the now-dropped SQL objects.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~3 minutes

Possibly related issues

• Move nico_inet_to_dns_hostname (instance DNS) from SQL to Rust #2709: This PR directly fulfills the objective of migrating instance DNS logic from SQL to Rust by removing the nico_inet_to_dns_hostname SQL function and dns_records_instance view, along with their associated integration tests.

Possibly related PRs

• NVIDIA/infra-controller#2691: Directly related — that PR introduced the Rust arpa_qname_to_ip parser and normalization logic that replaces the SQL-based hostname derivation being removed here; both PRs mutate crates/api-db/src/dns/mod.rs in the same functional area.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately and concisely summarizes the primary change: removing an unused DNS view and its supporting SQL function, directly reflecting the changeset.
Description check	✅ Passed	The description provides comprehensive context for the changes, explaining why the objects are unused, how functionality was replaced, and verification that removal is safe.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
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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[chet]

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🔍 Container Scan Summary

Service	Total	Critical	High	Medium	Low	Other
boot-artifacts-aarch64	3	0	0	3	0	0
boot-artifacts-x86_64	3	0	0	3	0	0
forge-admin-cli-x86_64	264	6	23	99	6	130
machine-validation-runner	704	34	183	258	35	194
machine_validation	704	34	183	258	35	194
nvmetal-carbide	704	34	183	258	35	194
TOTAL	2382	108	572	879	111	712

Per-CVE detail lives in the per-service grype-* artifacts (JSON + SARIF). Severity counts only — no CVE IDs published here.