Prevent divide-by-zero errors in cache_score function

[jc-harrison]

Closes #7027

I have:

• Formatted any Python files with black
• Brought the branch up to date with master
• Added any relevant Github labels
• Added tests for any new additions
• Added or updated any relevant documentation
• Added an Architectural Decision Record (ADR), if appropriate
• Added an MPLv2 License Header if appropriate
• Updated the Changelog

Description

We already had a safeguard in the FlowDB touch_cache function to increase table size to a non-zero value. This PR moves the safeguard into cache_score, so that it takes effect everywhere cache_score is used.

Summary by CodeRabbit

• Bug Fixes
  • Improved cache score calculation to prevent errors with very small or zero table sizes, ensuring more reliable performance when handling cache operations.

[coderabbitai]

Walkthrough

The update revises the handling of the tablesize parameter in SQL utility functions. The cache_score function now internally applies a lower bound to tablesize using the greatest function, and touch_cache is updated to pass raw values rather than pre-processed ones. Function signatures and internal logic were adjusted accordingly.

Changes

File(s)	Change Summary
flowdb/bin/build/0030_utilities.sql	Updated cache_score to apply greatest to tablesize internally; modified touch_cache to pass unprocessed tablesize directly to cache_score.

Assessment against linked issues

Objective	Addressed	Explanation
Ensure tablesize used in cache_score is always > 0 to prevent divide-by-zero errors (#7027)	✅

Poem

A hop, a skip, a database tweak,
Cache scores now stronger, never weak!
No more fears of zero divide,
With greatest guards now set inside.
Rabbits cheer with every run—
Safe and sound, the queries fun!
🐇✨

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[coderabbitai]

Actionable comments posted: 1

🧹 Nitpick comments (1)

flowdb/bin/build/0030_utilities.sql (1)

270-270: Internalise divide-by-zero guard in cache_score
Centralising the greatest(tablesize, 0.00001) check inside cache_score is an improvement for robustness. As an enhancement, consider declaring the function IMMUTABLE (since it has no side effects and depends only on its inputs) and adding the STRICT modifier to explicitly handle NULL inputs.

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• flowdb/bin/build/0030_utilities.sql (2 hunks)

⏰ Context from checks skipped due to timeout of 90000ms (3)

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[cypress]

FlowAuth    Run #24628

Run Properties:   Failed #24628  •  f17586679b: Merge branch 'fix-cache-score' of github.com:Flowminder/FlowKit into fix-cache-s...

Project	FlowAuth
Branch Review	fix-cache-score
Run status	Failed #24628
Run duration	03m 13s
Commit	f17586679b: Merge branch 'fix-cache-score' of github.com:Flowminder/FlowKit into fix-cache-s...
Committer	James Harrison
View all properties for this run ↗︎

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Test results
Failures	1
Flaky	3
Pending	0
Skipped	6
Passing	36
View all changes introduced in this branch ↗︎

---

Tests for review

  cypress/e2e/role_list.js • 1 failed test

View Output

Test		Artifacts
role list screen > Add blank role		Test Replay Screenshots

  add_new_server.js • 2 flaky tests

View Output

Test		Artifacts
Server management > Add duplicate Server name		Test Replay Screenshots
Server management > Add server		Test Replay Screenshots

  add_new_user.js • 1 flaky test

View Output

Test		Artifacts
User management > Add password with less strength		Test Replay Screenshots

[greenape]

LGTM. Worth adding a test case for the bug?