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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
1.4 KiB
Markdown
26 lines
1.4 KiB
Markdown
---
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bc-version: [all]
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domain: performance
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keywords: [n-plus-one, get, findfirst, loop, inner-lookup, large-table]
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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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# Avoid Get / FindFirst inside a loop on a large inner table
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## Description
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A `Get` or `FindFirst` against another persistent table inside a loop can produce an N+1 access pattern: one outer query followed by repeated inner lookups. Server and primary-key caches can satisfy some `Get` calls, so a source-level `Get` is not proof of one SQL round-trip. The concern is an unbounded loop whose lookup keys are not known to repeat or remain cached.
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## Best Practice
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Use a query object to join the outer and inner tables when the relationship and filters can be expressed as one query. If keys repeat, a dictionary cache can reduce lookups to one per distinct key. `SetLoadFields` can reduce the columns transferred by unavoidable inner reads, but it does not eliminate the N+1 shape and must not be presented as doing so.
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See sample: [`avoid-get-inside-loop-on-large-table.good.al`](avoid-get-inside-loop-on-large-table.good.al).
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## Anti Pattern
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Iterating production BOM lines and calling `Item.Get(BOMLine."No.")` for each line when the same result can be produced by a query joining Production BOM Line to Item. Partial loading alone is only a payload mitigation for this pattern.
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See sample: [`avoid-get-inside-loop-on-large-table.bad.al`](avoid-get-inside-loop-on-large-table.bad.al).
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