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* Add BC performance knowledge from OptimAL learnings Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> * Address review feedback on performance guidance Clarify predicate-supporting keys versus covering queries, demonstrate proven cache reuse, and evaluate the updated partial-load and bulk-update rules. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
26 lines
1.9 KiB
Markdown
26 lines
1.9 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [modifyall, deleteall, bulk, loop, modify, set-based]
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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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# Use ModifyAll only for equivalent bulk assignments
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## Description
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`ModifyAll` assigns one value to one field across the filtered set. It does not run the field's `OnValidate` trigger. Its optional `RunTrigger` parameter controls the table `OnModify` trigger, not field validation. Replacing a loop is therefore correct only when direct assignment is semantically equivalent for every row.
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## Best Practice
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Use `ModifyAll` when the loop directly assigns the same value, does not call `Validate`, needs no per-row calculation, and does not depend on `OnModify` unless the equivalent `RunTrigger` value is supplied. For a data-only update, exclude rows already holding the target value when that filter preserves the business outcome. Do not skip unchanged rows if the original call's per-row effects are required. Check whether table trigger code, related subscribers, security filtering, `Media`/`MediaSet`, or companion fields force row-by-row fallback (see `triggers-and-media-field-regress-modifyall.md`). A visible loop for progress UX is acceptable only when evidence shows the equivalent bulk call already executes as individual operations and the loop preserves trigger and business semantics.
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See sample: [`prefer-modifyall-over-per-row-modify.good.al`](prefer-modifyall-over-per-row-modify.good.al).
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## Anti Pattern
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A loop that only assigns a constant and calls `Modify(false)` on a field with no validation side effects or bulk fallback condition. A progress dialog alone does not exempt this loop. Conversely, replacing `Validate(Field, Value); Modify(true)` with `ModifyAll(Field, Value)` is also an anti-pattern because it silently drops field validation and may drop table-trigger behavior.
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See sample: [`prefer-modifyall-over-per-row-modify.bad.al`](prefer-modifyall-over-per-row-modify.bad.al).
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