WA-VERIFY-089: Fix embedded document count behavior change in Mongoid 8

[kitcommerce]

Summary

WA-VERIFY-083 (PR #1075) identified that Mongoid 8 changes embedded document .count behavior: it now always hits the database rather than using in-memory length. This can cause N+1 queries in code that calls .count on embedded associations.

Approach

# Find .count calls on embedded associations
grep -rn '\.count' app/models/ lib/ --include='*.rb' | grep -v '#.*count'

Audit all .count calls on embedded associations. Where in-memory length is semantically correct (already-loaded array), replace with .size or .length.

Acceptance Criteria

• Embedded association .count calls audited across all models
• In-memory count calls changed to .size where appropriate
• No performance regressions (N+1 queries introduced)
• Notes file documents the audit findings and changes

Client Impact

None expected (behavior unchanged; performance may improve).

Related

• Blocks: WA-RAILS7-004: Mongoid 8.x upgrade — implement changes from research doc #690 (WA-RAILS7-004 Mongoid 8 upgrade)
• Research: PR WA-VERIFY-083: Mongoid 8 upgrade readiness assessment (#1069) #1075 (WA-VERIFY-083 assessment)

[kitcommerce]

Review Wave 1 — Changes Requested

PR: #1087

Architecture review found a scope mismatch:

• PR body/notes claim embedded-association count→size fixes, but the current PR diff shows only a QueryCache migration (Mongoid::QueryCache → Mongo::QueryCache) + docs/notes.
• QueryCache migration is already represented by PR WA-VERIFY-086: migrate QueryCache to Mongo::QueryCache #1086 (closes WA-VERIFY-086: Fix Mongoid::QueryCache → Mongo::QueryCache API migration (Mongoid 8 Phase 1) #1077), so PR WA-VERIFY-089: use size for embedded association counts (Mongoid 8) #1087 appears to be duplicating that work.

Fix brief

• Update PR WA-VERIFY-089: use size for embedded association counts (Mongoid 8) #1087/branch so it actually contains the embedded-association count→size changes required by WA-VERIFY-089: Fix embedded document count behavior change in Mongoid 8 #1080.
• Remove unrelated QueryCache migration changes (and WA-VERIFY-086 notes/doc edits) from PR WA-VERIFY-089: use size for embedded association counts (Mongoid 8) #1087; keep that work in PR WA-VERIFY-086: migrate QueryCache to Mongo::QueryCache #1086.
• Align PR title/body + notes so they match the actual diff.
• Re-run build gate (rubocop diff-only + affected-engine tests).

Status moved to .

[kitcommerce]

Follow-up (quoting fix):

Fix PR #1087 on branch kit/1080-mongoid8-embedded-count so it actually contains the embedded-association count->size changes for #1080, and remove unrelated QueryCache migration changes + WA-VERIFY-086 notes/doc edits (that work belongs in PR #1086).

After updates: rerun rubocop diff-only + affected-engine tests, and ensure PR body/notes match the diff.

[kitcommerce]

Dispatcher: PR #1087 has been updated to include the embedded-association count→size changes for WA-VERIFY-089 (and now matches the issue). Moving back to status:ready-for-review.