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- performance/use-setloadfields-for-partial-records: Clarify that filter-only fields (SetRange/SetFilter) do not need to be listed in SetLoadFields — the DB resolves them via the index without hydrating the value into AL memory. - performance/avoid-calcfields-in-loops: Add explicit exception for OnAfterGetRecord and OnValidate triggers, which are platform-managed and not developer-authored loops. - performance/split-read-only-and-write-paths-to-avoid-locktable: Add ReadIsolation as the primary recommendation for read-only paths; LockTable reserved for confirmed write paths only. - performance/prefer-direct-record-over-recordref: Scope the finding to hot unbounded loops (10k+ rows) over ledger-entry-scale tables; RecordRef in bounded/admin/setup contexts is not a concern. - upgrade/enum-changes-must-be-additive-at-the-end: Replace direct ObsoleteState = Removed guidance with the two-stage workflow (Pending first, Removed later); reference use-obsolete-pending-before-removed. - upgrade/use-datatransfer-for-large-dataset-initialization: Add the >300,000 records threshold as the concrete trigger for requiring DataTransfer. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
29 lines
1.6 KiB
Markdown
29 lines
1.6 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [calcfields, flowfield, loop, n-plus-one]
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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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# Do not call CalcFields inside loops
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## Description
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CalcFields evaluates one or more FlowFields for the current record by issuing a separate SQL aggregation. Called inside a loop over a record set, it becomes an N+1 problem: one aggregate per row. For any non-trivial set on a ledger-entry-backed FlowField this is orders of magnitude slower than the equivalent batched query.
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## Best Practice
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Move CalcFields out of the iteration. If the total is what you need, use CalcSums on the filtered parent set. If row-by-row FlowField values are needed, reshape the computation so the aggregate runs once — for example by joining against a temporary table populated in a single batched query.
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**Acceptable exceptions:** CalcFields inside an `OnAfterGetRecord` page trigger is the standard pattern for displaying computed FlowField values — the platform calls this trigger once per row and it is not a developer-authored loop. Similarly, CalcFields inside an `OnValidate` field trigger fires at most once per user action and is acceptable. The concern is only developer-written `FindSet … repeat … until Next() = 0` loops.
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See sample: `avoid-calcfields-in-loops.good.al`.
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## Anti Pattern
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Calling CalcFields inside `repeat ... until Next() = 0` on a hot parent record is the textbook N+1 pattern. Even a modest parent set size (hundreds of rows) turns into thousands of round-trips.
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See sample: `avoid-calcfields-in-loops.bad.al`.
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