--- id: change/bcquality/198 type: change title: "#198 Add BC performance knowledge from OptimAL learnings" summary: Adds six performance knowledge articles with paired good and bad AL examples on workload-based and overlapping indexes, buffered inserts, aggregate-before-write, scoped reuse and repeated validation. Refines existing guidance on partial loads, temporary buffers, bulk updates, existence checks, primary-key caching and FlowField versus stored totals. tier: official language: en tags: - feature - main system: platform review: state: reviewed by: opus at: "2026-10-08T02:03:52.830Z" flags: [] generated: at: "2026-10-08T01:26:53.141Z" pipeline: 0.2.0 prompts: extract-change: 1 input_hash: 87ba36e650dde6a1cd4c1bd499303cbde3a6a47f evidence: - kind: code url: https://github.com/microsoft/BCQuality/pull/198 title: "microsoft/BCQuality#198: Add BC performance knowledge from OptimAL learnings" date: "2026-09-29" commit: 87ba36e650dde6a1cd4c1bd499303cbde3a6a47f t: null quote: null links: learn: [] objects: [] features: [] topics: [] localizations: [] videos: [] posts: [] guidelines: [] changes: [] number: 198 repo: microsoft/BCQuality source_id: bcquality-prs url: https://github.com/microsoft/BCQuality/pull/198 kind: pr base_branch: main major: null merged_at: "2026-09-29T15:21:29Z" author: JesperSchulz author_type: User community_contribution: false labels: [] change_class: code change_kind: feature behavior_change: false breaking: false files: count: 37 additions: 920 deletions: 37 al: 36 apps: [] objects_touched: [] objects_unjoined: - path: microsoft/knowledge/performance/aggregate-before-persisting-intermediate-results.bad.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/aggregate-before-persisting-intermediate-results.good.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/aggregate-before-persisting-intermediate-results.md status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/avoid-get-inside-loop-on-large-table.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/avoid-repeating-unchanged-validation.bad.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/avoid-repeating-unchanged-validation.good.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/avoid-repeating-unchanged-validation.md status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/cache-repeated-filtered-results-with-explicit-scope.bad.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/cache-repeated-filtered-results-with-explicit-scope.good.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/cache-repeated-filtered-results-with-explicit-scope.md status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/calcsums-instead-of-calcfields-in-loop.bad.al status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/calcsums-instead-of-calcfields-in-loop.good.al status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/calcsums-instead-of-calcfields-in-loop.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/design-covering-keys-from-read-pattern.bad.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/design-covering-keys-from-read-pattern.good.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/design-covering-keys-from-read-pattern.md status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/isempty-before-findset-is-extra-round-trip.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/prefer-modifyall-over-per-row-modify.good.al status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/prefer-modifyall-over-per-row-modify.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/preserve-buffered-inserts-by-separating-target-reads.bad.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/preserve-buffered-inserts-by-separating-target-reads.good.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/preserve-buffered-inserts-by-separating-target-reads.md status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/primary-key-get-in-loop-is-transaction-cached.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/query-results-bypass-primary-key-cache.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/review-overlapping-keys-before-adding-an-index.bad.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/review-overlapping-keys-before-adding-an-index.good.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/review-overlapping-keys-before-adding-an-index.md status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/setcurrentkey-sets-sort-order-not-index-hint.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/temporary-tables-have-no-database-cost.bad.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/temporary-tables-have-no-database-cost.good.al status: added reason: not-in-snapshot - path: microsoft/knowledge/performance/temporary-tables-have-no-database-cost.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/use-setautocalcfields-for-per-row-flowfields.md status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/use-setloadfields-for-partial-records.bad.al status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/use-setloadfields-for-partial-records.good.al status: modified reason: not-in-snapshot - path: microsoft/knowledge/performance/use-setloadfields-for-partial-records.md status: modified reason: not-in-snapshot - path: microsoft/skills/review/al-performance-review.md status: modified reason: not-in-snapshot obsoletions: [] backports: [] fixes_issues: [] work_items: [] systems: - platform - development quote: null joined_against: major: null commit: null --- # #198 Add BC performance knowledge from OptimAL learnings > Adds six performance knowledge articles with paired good and bad AL examples on workload-based and overlapping indexes, buffered inserts, aggregate-before-write, scoped reuse and repeated validation. Refines existing guidance on partial loads, temporary buffers, bulk updates, existence checks, primary-key caching and FlowField versus stored totals. [Pull request](https://github.com/microsoft/BCQuality/pull/198) · merged into `main` on 2026-09-29 by JesperSchulz · 37 files (+920 -37), 36 AL · feature · tier official · reviewed (checked by Opus) ## What changed - Six new articles on workload-based keys, overlapping indexes, buffered inserts, aggregate-before-write, scoped result reuse and repeated validation - Each new article has paired good and bad AL examples - Existing guidance refined for partial loads, temporary buffers, bulk updates, existence checks, primary-key caching and FlowField versus stored-field totals - SIFT-specific SetCurrentKey case clarified - Performance-review retrieval and evaluation fixtures extended for the new rules ## AL objects touched - `microsoft/knowledge/performance/aggregate-before-persisting-intermediate-results.bad.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/aggregate-before-persisting-intermediate-results.good.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/aggregate-before-persisting-intermediate-results.md`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/avoid-get-inside-loop-on-large-table.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/avoid-repeating-unchanged-validation.bad.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/avoid-repeating-unchanged-validation.good.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/avoid-repeating-unchanged-validation.md`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/cache-repeated-filtered-results-with-explicit-scope.bad.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/cache-repeated-filtered-results-with-explicit-scope.good.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/cache-repeated-filtered-results-with-explicit-scope.md`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/calcsums-instead-of-calcfields-in-loop.bad.al`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/calcsums-instead-of-calcfields-in-loop.good.al`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/calcsums-instead-of-calcfields-in-loop.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/design-covering-keys-from-read-pattern.bad.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/design-covering-keys-from-read-pattern.good.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/design-covering-keys-from-read-pattern.md`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/isempty-before-findset-is-extra-round-trip.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/prefer-modifyall-over-per-row-modify.good.al`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/prefer-modifyall-over-per-row-modify.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/preserve-buffered-inserts-by-separating-target-reads.bad.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/preserve-buffered-inserts-by-separating-target-reads.good.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/preserve-buffered-inserts-by-separating-target-reads.md`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/primary-key-get-in-loop-is-transaction-cached.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/query-results-bypass-primary-key-cache.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/review-overlapping-keys-before-adding-an-index.bad.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/review-overlapping-keys-before-adding-an-index.good.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/review-overlapping-keys-before-adding-an-index.md`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/setcurrentkey-sets-sort-order-not-index-hint.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/temporary-tables-have-no-database-cost.bad.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/temporary-tables-have-no-database-cost.good.al`: added, not in the BC? snapshot yet - `microsoft/knowledge/performance/temporary-tables-have-no-database-cost.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/use-setautocalcfields-for-per-row-flowfields.md`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/use-setloadfields-for-partial-records.bad.al`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/use-setloadfields-for-partial-records.good.al`: modified, not in the BC? snapshot - `microsoft/knowledge/performance/use-setloadfields-for-partial-records.md`: modified, not in the BC? snapshot - `microsoft/skills/review/al-performance-review.md`: modified, not in the BC? snapshot ## Context - Systems: platform, development Source: metadata of a merged pull request in microsoft/BCQuality (bcquality): title, labels, changed paths and counts, with a summary in our words. No source text and no description beyond one short quote (D10, D61).