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Ports 14 concern-sized articles (8 performance, 6 security) and 25
AL samples from BC Code Intelligence, restructured to BCQuality's v1
schema and layered under /community/knowledge/. Each article is
atomic, under 100 lines, and ships <slug>.good.al and (where the
pattern has a clear anti-example) <slug>.bad.al siblings.
Jesper's microsoft-layer leaves (al-performance-review and
al-security-review) source across every enabled layer via
*/knowledge/<domain>/**, so these additions are picked up by the
existing action skills without any new skill definitions.
Performance (8):
- use-deleteall-for-filtered-bulk-deletion
- call-setloadfields-before-filters
- load-common-fields-before-branching-on-case
- load-only-primary-key-fields-for-reference-work
- omit-filter-only-fields-from-setloadfields
- choose-maintainsiftindex-by-read-write-ratio
- avoid-growing-globals-in-singleinstance-subscribers
- order-case-branches-by-frequency
Security (6):
- classify-every-field-with-dataclassification
- protect-sensitive-data-in-temporary-tables
- guard-bulk-operations-with-istemporary
- compose-permission-sets-with-included-sets
- do-not-grant-rights-beyond-a-users-entitlement
- prefer-oauth2-over-api-keys-for-external-http-calls
Graveyard-bound items (not ported; to be captured in a later
/docs/triage-graveyard.md):
- testfield-performance (soft guidance, low actionability)
- table-event-batch-operation-impact (keep-event-subscribers-lightweight
already carries the core insight)
- Most of /roger-reviewer (AL formatting - frontier-model territory)
- sift-technology-fundamentals (descriptive, not a citable concern)
- bc-telemetry-buddy-* (tooling promotion, not guidance)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
28 lines
1.7 KiB
Markdown
28 lines
1.7 KiB
Markdown
---
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bc-version: [26..28]
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domain: performance
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keywords: [singleinstance, subscriber, event, memory, session]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Avoid growing globals in SingleInstance subscribers
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> **Seed article.** Ported from BC Code Intelligence to seed the community corpus. Community contributors are invited to expand or refine.
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## Description
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A codeunit with `SingleInstance = true` is allocated once per session and lives until the session ends. Global variables on it are never collected between event fires. A subscriber that accumulates data into a global — buffering payloads, appending to a list, caching without a cap — steadily grows its session footprint for the entire user session. The symptom is memory that only recovers on sign-out, and it surfaces only on long-running sessions.
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## Best Practice
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Keep the global footprint on a SingleInstance subscriber bounded and intentional: a handful of flags, a setup record, a bounded cache with a maximum size. When cross-event state is genuinely needed, define an explicit reset point — end of a business process, arrival of a specific terminal event — that clears the growing collection.
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See sample: `avoid-growing-globals-in-singleinstance-subscribers.good.al`.
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## Anti Pattern
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A SingleInstance subscriber that appends each event's payload to a global list, dictionary, or temporary record without a cap or cleanup trigger. The list grows for hours, memory pressure builds quietly, and debugging the root cause on a live environment is substantially harder than noticing the unbounded append in code review.
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See sample: `avoid-growing-globals-in-singleinstance-subscribers.bad.al`.
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