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28 lines
1.6 KiB
Markdown
28 lines
1.6 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [setloadfields, case, conditional, branch, field-loading]
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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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# Load common fields before branching on case
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> Contributions welcome — open a PR to refine or extend this article.
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## Description
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When record processing branches on state, different branches typically read different fields. A single `SetLoadFields` at the top listing every field any branch might touch pulls more data than any individual execution path needs — on the hot path, the rest is loaded for nothing. A two-tier approach matches loading to actual usage: load the fields the `case` expression evaluates plus any fields every branch uses, then add a branch-local `SetLoadFields` inside each branch for that branch's extra fields.
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## Best Practice
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Before the `case`, call `SetLoadFields` with the minimal set — the discriminator field and fields common to every branch. Inside each branch, before the first access to a branch-specific field, add a second `SetLoadFields` covering those fields. The platform honors the in-branch call for the next record operation, so the extra data is fetched only when the branch runs.
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See sample: `load-common-fields-before-branching-on-case.good.al`.
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## Anti Pattern
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A single top-level `SetLoadFields` enumerating every field any branch might read. On records whose state routes them to the fast common branch, the rarely-needed fields are still loaded — the optimization becomes a net-neutral or net-negative change on the hot path.
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See sample: `load-common-fields-before-branching-on-case.bad.al`.
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