a9f3c50863
The previous LLM-generated knowledge files contained factual
hallucinations. The most visible was the claim that `FindFirst` /
`FindLast` "forces a full-table scan" on an unfiltered record - it does
not; those APIs return a single row via the current key.
Other inaccuracies the audit found and fixed:
* `FindSet(true)` was described as "taking a LockTable". The correct
upstream phrasing is that `FindSet(true)` sets
`ReadIsolation::UpdLock` on the read. UpdLock and LockTable are
related but distinct mechanisms.
* The list of production-scale tables had been invented beyond the
upstream source (e.g. "Detailed Cust. Ledg. Entry") without a
citation. The regenerated list matches the ten tables upstream lists
with their P95 row counts.
* `SetLoadFields` guidance had been augmented with an extra mechanism
claim ("the database resolves the filter using the index without
hydrating the value") not present in upstream.
Approach: full regeneration of `microsoft/knowledge/` from the six
upstream BCApps Code Review instruction files, with Microsoft Learn /
the AL language reference as a secondary source. Every claim in every
regenerated file is anchored to a verbatim upstream quote (or a Learn
URL); the audit trail lives in artifacts/trace-<domain>.json on the
session workspace.
The PR #11 transaction/error-handling cluster is preserved verbatim:
* performance/understand-implicit-transaction-boundary.md
* performance/codeunit-run-as-atomic-sub-operation.{md,good.al,bad.al}
* performance/codeunit-run-requires-prior-commit-inside-transaction.{md,good.al,bad.al}
* performance/use-tryfunction-for-error-catching-not-rollback.{md,good.al,bad.al}
* performance/avoid-commit-inside-loops.{md,good.al,bad.al}
* security/commitbehavior-attribute-scopes-explicit-commits.{md,good.al,bad.al}
* testing/transactionmodel-attribute-governs-test-transactions.{md,good.al,bad.al}
These articles already cite Microsoft Learn and were carefully
cross-referenced; the regeneration skips their topics rather than
duplicating them.
File counts after regeneration:
performance 35 .md (5 preserved + 30 new)
privacy 17 .md
security 18 .md (1 preserved + 17 new)
style 33 .md
testing 1 .md (preserved)
ui 19 .md
upgrade 18 .md
Total 141 atomic knowledge files, each strictly one rule. All pass
.github/scripts/validate_frontmatter.py with 0 errors and 0 warnings.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
2 KiB
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Use SetLoadFields to load only the fields the code reads
Description
SetLoadFields(...) declares the subset of normal fields the next read should materialize, "reducing data read and transfer thereby improving performance significantly." Per the upstream guidance, "the gains scale with the amount of rows read, so for loops that read many rows SetLoadFields is even more important." Primary-key fields, SystemId, and system audit fields are loaded automatically, "and fields that are filtered on are also automatically included" — those do not need to appear in the list. SetLoadFields only affects FieldClass = Normal; it does not narrow FlowFields or FlowFilters.
Best Practice
Before a Get, FindSet, or FindFirst that the procedure follows by reading only a handful of the table's fields, call SetLoadFields listing exactly those fields. The pattern SetLoadFields(...); if Record.Get(...) then ... is the upstream-endorsed shape. Skip SetLoadFields when the table has few fields (under ten), when the code reads most of them (above 60 %), when the loop runs ten or fewer iterations, or when the table is exempt for other reasons (singleton-setup-tables-need-no-access-optimization.md, temporary-tables-have-no-database-cost.md). For report dataitems, use AddLoadFields in OnPreDataItem instead (see addloadfields-in-report-onpredataitem.md).
See sample: use-setloadfields-for-partial-records.good.al.
Anti Pattern
Loading a wide table and reading one field per row in a loop. The bytes transferred per row are dominated by the columns the procedure does not touch; the SQL query selects them anyway. The same applies to a single Get on a wide table — the platform reads the whole row when a single field would have sufficed.
See sample: use-setloadfields-for-partial-records.bad.al.