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Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> Copilot-Session: 667c64a8-eb36-4440-bc41-6a97d8fb5542
28 lines
1.4 KiB
Markdown
28 lines
1.4 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 a known input determines which fields a subsequent record read will use, a single `SetLoadFields` containing every branch's fields loads unnecessary columns. Build the selection before `Get`, `FindFirst`, or `FindSet`: use `SetLoadFields` for fields common to every branch, then `AddLoadFields` for the selected branch. `SetLoadFields` replaces the current selection, while `AddLoadFields` preserves it.
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## Best Practice
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Call `SetLoadFields` with the common fields. In each branch, call `AddLoadFields` with that branch's normal fields and then perform the record read. This applies only when the discriminator is known before the read; branching on a field from an already-loaded row is too late to tailor that row's initial SQL projection.
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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 branch's fields, or a branch-local `SetLoadFields` that accidentally discards the common selection. Both make the declared load plan differ from the fields the selected path actually uses.
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See sample: `load-common-fields-before-branching-on-case.bad.al`.
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