bcquality/microsoft/knowledge/performance/skip-setloadfields-on-narrow-tables-and-short-loops.md
Jesper Schulz-Wedde e570d6113f Extract 55 knowledge articles from BC review-agent prompt
Adds 55 articles (plus 76 code samples) spanning four new domains and
two existing domains, extracted from the internal Business Central
review-agent prompt. Content was filtered against BCQuality's
remedial-knowledge premise: each article encodes BC-specific behaviour,
a CodeCop rule, a platform API semantic, or an anti-false-positive
guideline that a capable LLM would otherwise get wrong.

New domains:
- privacy (11 articles): DataClassification inheritance semantics, the
  StrSubstNo-defeats-Error-telemetry-classification pitfall, Privacy
  Notice consent for outgoing requests, anti-false-positives for pages
  and in-memory data.
- upgrade (11 articles): upgrade-codeunit structure, upgrade-tag
  lifecycle and registration, protected DB reads, DataTransfer for
  large datasets, InitValue semantics, enum-ordinal preservation,
  obsolete-workflow, first-install detection.
- ui (9 articles): caption capitalization by phrase type, tooltip voice,
  teaching-tip vs tooltip, tour-tip conventions, character limits,
  banned terms, ampersand handling, title punctuation.
- style (11 articles): label-suffix convention, API page naming,
  temporary-variable prefix, label properties (Comment/Locked), named
  invocations, FieldCaption in user messages, OptionCaption pairing,
  Error-parameter passing, `this` keyword, required parentheses, file
  naming.

Gaps in existing domains:
- performance (11 articles): production-scale table catalog (no row
  counts, per internal-data concern), anti-false-positive for bounded
  tables, guard-before-Get ordering, redundant-Get-in-OnAfterGetRecord,
  LockTable in read-only helpers, combined ModifyAll passes, writes in
  OnAfterGetRecord, SetLoadFields heuristics, temporary-table
  regressions, FlowField source-table widening, MaintainSQLIndex
  disabling SIFT.
- security (2 articles): environment-specific hardcoded GUIDs,
  ValidateTableRelation=false on user input.

Intentionally excluded: specific production P95 row-count numbers
(aggregated internal telemetry); rewritten as categorical guidance on
which tables to treat as production-scale without publishing sizes.

All articles use `bc-version: [all]` (applies to every BC version, per
the new schema sentinel). Validator passes with 0 errors / 0 warnings.
2026-04-23 16:43:42 +02:00

22 lines
1.8 KiB
Markdown

---
bc-version: [all]
domain: performance
keywords: [setloadfields, heuristics, narrow-table, short-loop, diminishing-returns]
technologies: [al]
countries: [w1]
application-area: [all]
---
# SetLoadFields pays off at scale; skip it on narrow tables and short loops
## Description
`SetLoadFields` reduces the number of columns the platform hydrates per record. It delivers real savings on wide tables with blob, media, or many text fields when the iteration touches a small subset. Below certain thresholds the accounting flips the other way: narrow tables (fewer than ~10 fields) save almost nothing per row, and short loops (fewer than ~10 iterations) amortize the narrowing over too few fetches to outweigh the extra code and the specification-and-access-set coupling that future edits have to maintain. Recommending SetLoadFields on every Find/Get call produces low-value churn and invites the opposite mistake — listing a field in SetLoadFields and then forgetting to access it, which triggers a second round-trip to load the missing field.
## Best Practice
Reach for SetLoadFields when the table is wide (10+ fields, especially with blobs) AND the code path reads a small subset AND the iteration or fetch count is material. When in doubt on a short loop over a narrow table, leave SetLoadFields out; the complexity cost is not earned. The filter-only-field rule from `omit-filter-only-fields-from-setloadfields` still applies: fields used only in filters stay out of the list.
## Anti Pattern
A 5-row loop over a 6-field setup table prefaced by `Rec.SetLoadFields(...)`. The author has added two lines of code, coupled the loop to a field specification that needs to be updated on every schema change, and saved nanoseconds. The same pattern applied mechanically to every Find call in a codebase produces hundreds of diffs that do not move the performance needle.