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Most of the corpus — FindSet/SetLoadFields/CalcFields patterns, permission sets, SingleInstance codeunits, DataClassification, IsolatedStorage, transaction scope, SecretText — describes BC platform behaviour that is identical across supported versions. The seed [26..28] range on every file implied a version-specificity the content does not actually have, and there was no way to express "applies to every version" in the schema the way [w1] and [all] already do for countries and application-area. Extend the v1 schema with a universal sentinel for bc-version, parallel to the sentinels already defined for the other dimensions: bc-version: [all] # applies to every BC version [all] is mutually exclusive with explicit versions. Range shorthand ([26..28]) and explicit lists ([26, 27, 28]) continue to work for files genuinely tied to a version-gated API or deprecation. Update read.md (field definition, matching semantics, partial-context rule), write.md (default to [all], use ranges only with a concrete reason), README.md (frontmatter example), and the CI validator. All forty existing knowledge files and the three action skills convert to [all]; none of the current content is version-gated. Validator passes.
28 lines
1.7 KiB
Markdown
28 lines
1.7 KiB
Markdown
---
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bc-version: [all]
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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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