bcquality/microsoft/knowledge/performance/avoid-calcfields-in-loops.md
Jesper Schulz-Wedde 9a4198eb28 Add [all] sentinel to bc-version; apply to version-agnostic knowledge
Most of the corpus — FindSet/SetLoadFields/CalcFields patterns, permission
sets, SingleInstance codeunits, DataClassification, IsolatedStorage,
transaction scope, SecretText — describes BC platform behaviour that is
identical across supported versions. The seed [26..28] range on every
file implied a version-specificity the content does not actually have,
and there was no way to express "applies to every version" in the
schema the way [w1] and [all] already do for countries and
application-area.

Extend the v1 schema with a universal sentinel for bc-version, parallel
to the sentinels already defined for the other dimensions:

  bc-version: [all]         # applies to every BC version

[all] is mutually exclusive with explicit versions. Range shorthand
([26..28]) and explicit lists ([26, 27, 28]) continue to work for files
genuinely tied to a version-gated API or deprecation.

Update read.md (field definition, matching semantics, partial-context
rule), write.md (default to [all], use ranges only with a concrete
reason), README.md (frontmatter example), and the CI validator. All
forty existing knowledge files and the three action skills convert to
[all]; none of the current content is version-gated. Validator passes.
2026-04-23 16:00:03 +02:00

1.1 KiB

bc-version domain keywords technologies countries application-area
all
performance
calcfields
flowfield
loop
n-plus-one
al
w1
all

Do not call CalcFields inside loops

Description

CalcFields evaluates one or more FlowFields for the current record by issuing a separate SQL aggregation. Called inside a loop over a record set, it becomes an N+1 problem: one aggregate per row. For any non-trivial set on a ledger-entry-backed FlowField this is orders of magnitude slower than the equivalent batched query.

Best Practice

Move CalcFields out of the iteration. If the total is what you need, use CalcSums on the filtered parent set. If row-by-row FlowField values are needed, reshape the computation so the aggregate runs once — for example by joining against a temporary table populated in a single batched query.

See sample: avoid-calcfields-in-loops.good.al.

Anti Pattern

Calling CalcFields inside repeat ... until Next() = 0 on a hot parent record is the textbook N+1 pattern. Even a modest parent set size (hundreds of rows) turns into thousands of round-trips.

See sample: avoid-calcfields-in-loops.bad.al.