perf(templates): avoid loading group members and batch list relations

[dr-hoseyn]

Summary

Creating or updating a user template currently loads every user and inbound in its selected groups, although only the group association is needed. Listing templates also loads groups once per template. Disable those unnecessary group relationship loads on create/update and use selectinload(UserTemplate.groups) for lists, preserving responses, filters, and pagination.

Measured improvement

Local before/after comparison against dev at 26047f6b, using the actual CRUD implementations on Python 3.14 / SQLite in memory:

Measurement	Before	After	Reduction
Create template with a 10,000-user group: median elapsed time	266.61 ms	6.63 ms	97.51%
Same operation: peak traced Python allocations	17.935 MiB	0.0607 MiB	99.66%
User objects loaded during creation	10,000	0	100%
SELECT statements for creation	5	3	40%
SELECT statements for a list of 100 templates	101	2	98.02%

Timing uses five alternating measurements per implementation after one warmup each, with a fresh session per call and response validation included. Memory was measured separately with tracemalloc; it is not process RSS. These are local synthetic CRUD measurements, not end-to-end API latency or a production guarantee. Larger lists use SQLAlchemy's select-in batches.

Type of change

• Refactor / cleanup (performance)

Checklist

• Tested locally.
• Existing tests and additional local regression checks passed; no test or benchmark files included.
• No documentation, translation, API, model, or migration changes required.
• No secrets or unrelated changes included; only app/db/crud/user_template.py changes.

Testing

• pytest tests/api/test_user_template.py -q --tb=short: 16 passed, with both DATABASE_URL and SQLALCHEMY_DATABASE_URL pointing to the same isolated temporary SQLite database.
• Local before/after regression checks: equivalent serialized create/update/list responses; group reassignment; empty/omitted update group IDs; ID filters; pagination; empty results; zero user loads during optimized updates.
• ruff check --no-fix app/db/crud/user_template.py, ruff format --check app/db/crud/user_template.py, and git diff --check: passed.
• Repository-wide ruff check --no-fix . reports seven pre-existing issues in unchanged files; the modified file is clean.

Screenshots

Not applicable.

Notes for reviewers

The existing group validation and authorization paths remain intact. PR #785 adds template ownership and does not implement this loading optimization; PR #772 optimizes group summaries rather than template CRUD. This PR targets dev, as next referenced in CONTRIBUTING no longer exists.

Summary by CodeRabbit

• Performance
  • Improved loading of user templates and their associated groups by avoiding unnecessary related data, while keeping the information available with templates.

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• app/db/crud/user_template.py

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Walkthrough

User template creation and modification fetch associated groups without loading users or inbounds. User template retrieval eagerly loads groups and no longer runs a separate attribute-loading loop.

Changes

User template group loading

Layer / File(s)	Summary
Fetch groups for template mutations app/db/crud/user_template.py	create_user_template and modify_user_template fetch associated groups with user and inbound loading disabled.
Eagerly load groups in template retrieval app/db/crud/user_template.py	get_user_templates eagerly loads groups and returns query results without the per-template attribute-loading loop.

Priority: ⬇️ Low

Estimated code review effort: 2 (Simple) | ~10 minutes

Change: Refactor

Suggested reviewers: m03ed

Merge Risk: ⚪ Minimal · up to 82c69

Template responses retain their group IDs, and no merge-blocking issue was identified.

🚥 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 clearly and concisely describes the main changes: avoiding group-member loading and batching list relationship loading.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 3 functions across 1 files.
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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_{A rabbit checks the template rows,
Where eager-loaded group data flows.
No users or inbounds tag along,
The loading loop is gone before long.
Soft paws hop through the query night,
Group links arrive in tidy flight.}

_{Comment @coderabbitai help to get the list of available commands.}

[dr-hoseyn]

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