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bcquality/microsoft/knowledge/performance/query-results-bypass-primary-key-cache.md
Jesper Schulz-Wedde 87ba36e650
Add BC performance knowledge from OptimAL learnings (#198) 
* 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>

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Co-authored-by: Jesper Schulz-Wedde <jesper.schulzwedde@microsoft.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
2026-09-29 17:21:28 +02:00

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bc-version domain keywords technologies countries application-area
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performance
query
primary-key-cache
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false-positive
n-plus-one
record-cache
al
w1
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Query results bypass the primary-key cache

Contributions welcome — open a PR to refine or extend this article.

Description

The Business Central server caches primary-key Get calls within a transaction. Query objects do not use that primary-key cache: reopening a Query per lookup executes the query again; Read consumes rows from an open query, not a new query for each row. avoid-get-inside-loop-on-large-table.md is right when an unbounded inner Get/FindFirst joins two large sets. It is wrong as a blanket rewrite of repeated Get on the same keys. Replacing a cached Get with a Query reopened per call can be slower.

Best Practice

Keep Record.Get for repeated lookups of the same primary keys in one transaction. Use a Query when the work is a true join or aggregation that the record API would express as nested scans. Do not flag a guarded Get on a repeating key as an N+1 solely because a Query could express the same columns.

See sample: query-results-bypass-primary-key-cache.good.al.

Anti Pattern

Rewriting a helper that Gets Customer by No. on every sales line into a Query opened inside that helper. Distinct line customers still need a lookup; repeating customers were already served from the PK cache. The Query pays SQL every time.

See sample: query-results-bypass-primary-key-cache.bad.al.