87ba36e650
* Add BC performance knowledge from OptimAL learnings Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> * Address review feedback on performance guidance Clarify predicate-supporting keys versus covering queries, demonstrate proven cache reuse, and evaluate the updated partial-load and bulk-update rules. Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com> --------- Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com> Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
1.7 KiB
| bc-version | domain | keywords | technologies | countries | application-area | |||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
|
performance |
|
|
|
|
IsEmpty immediately before FindSet is an extra round-trip
Contributions welcome — open a PR to refine or extend this article.
Description
IsEmpty is the right API when the caller only needs existence — see microsoft/knowledge/performance/use-isempty-for-existence-check.md. It is not a cheap guard in front of a loop that will FindSet anyway. FindSet already returns false when the filter matches nothing; an extra IsEmpty is unnecessary AL work and can issue a second database request, depending on caching. Agents and reviewers often insert if not Rec.IsEmpty() then "for performance" and duplicate a result the iterator already provides.
Best Practice
When the body iterates, open with if Rec.FindSet() then repeat ... until Next() = 0. Do not flag a bare FindSet loop as missing an IsEmpty precondition. Reserve IsEmpty for branches that never materialize the row set. An early check before a bulk write or lock is a different, workload-dependent decision: it can help when the filtered set is usually empty, but adds work when rows exist and does not lock the set against change.
See sample: isempty-before-findset-is-extra-round-trip.good.al.
Anti Pattern
if not Rec.IsEmpty() then if Rec.FindSet() then repeat. Also a false-positive review comment that asks to add that guard. The second read does not avoid the first; it duplicates it.
See sample: isempty-before-findset-is-extra-round-trip.bad.al.