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>
1.6 KiB
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Do not LockTable in a read-only procedure
Description
LockTable is a transaction-wide signal: from the call onward, every read against that table in the same transaction acquires UPDLOCK. Per the upstream guidance, "LockTable() before Modify/Insert/Delete in the same procedure is the correct pattern" — locking the read against the write that follows is what the call exists for. The anti-pattern is "LockTable() in read-only procedures — unnecessary lock contention": the procedure never writes, but the lock cost is paid by everyone sharing the transaction.
Best Practice
Reserve LockTable for the read directly before a Modify, Insert, or Delete that depends on the read value. If a helper is sometimes called for reading and sometimes for writing, split it into separate read and write paths and call LockTable only on the write path. For read-only existence checks or lookups, the right primitive is ReadIsolation (see prefer-readisolation-over-locktable-for-reads.md).
See sample: do-not-locktable-in-read-only-procedure.good.al.
Anti Pattern
A pure getter that opens with Rec.LockTable();. Every caller's transaction now acquires UPDLOCK on that table for every subsequent read until commit. The contention shows up as blocking on unrelated sessions whose own code path looks innocent — the locker is invisible to the blocked reader.
See sample: do-not-locktable-in-read-only-procedure.bad.al.