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2b5550c346
Lead with a complete plugin quick start and add task-oriented usage, troubleshooting, customization, and contribution guides. Preserve the broader plugin framing, correct conflicting contract guidance, support Agents folder reviews, and align repository validation. Convert existing sample references to clickable links without changing knowledge rules. Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
26 lines
1.8 KiB
Markdown
26 lines
1.8 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [calcfields, calcsums, loop, flowfield, n-plus-one, aggregation]
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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 CalcSums to aggregate, not CalcFields inside a loop
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## Description
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`CalcFields` materializes FlowField values for one record. Each call against a persistent table is "a separate SQL query"; running it inside a `repeat ... until Next() = 0` over a large table issues one query per row on top of the iteration itself. `CalcSums` answers the same aggregation question — "give me the sum of this FlowField over the filtered set" — as a single SQL statement. Per the upstream guidance, `CalcFields` inside loops on large persistent tables is "a performance problem"; the aggregation form is `CalcSums()`.
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## Best Practice
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When the procedure totals a FlowField (or several) across a filtered set, set the filters, then call `CalcSums("Field 1", "Field 2", ...)`. The platform issues one query; the result is read off the record's FlowField slot. Single `CalcFields` outside loops is fine, and `CalcFields` on the current row in a page's `OnAfterGetRecord` or in `OnValidate` is the standard pattern — those are per-action, not per-row over a large set.
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See sample: [`calcsums-instead-of-calcfields-in-loop.good.al`](calcsums-instead-of-calcfields-in-loop.good.al).
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## Anti Pattern
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`if CustLedgerEntry.FindSet() then repeat CustLedgerEntry.CalcFields("Remaining Amount"); Total += CustLedgerEntry."Remaining Amount"; until CustLedgerEntry.Next() = 0;` — exactly the upstream-flagged shape. The iteration is the cheap part; the per-row `CalcFields` is what scales linearly with table size.
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See sample: [`calcsums-instead-of-calcfields-in-loop.bad.al`](calcsums-instead-of-calcfields-in-loop.bad.al).
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