bcquality/microsoft/knowledge/performance/combine-multiple-modifyall-calls.md
Jesper Schulz-Wedde e570d6113f Extract 55 knowledge articles from BC review-agent prompt
Adds 55 articles (plus 76 code samples) spanning four new domains and
two existing domains, extracted from the internal Business Central
review-agent prompt. Content was filtered against BCQuality's
remedial-knowledge premise: each article encodes BC-specific behaviour,
a CodeCop rule, a platform API semantic, or an anti-false-positive
guideline that a capable LLM would otherwise get wrong.

New domains:
- privacy (11 articles): DataClassification inheritance semantics, the
  StrSubstNo-defeats-Error-telemetry-classification pitfall, Privacy
  Notice consent for outgoing requests, anti-false-positives for pages
  and in-memory data.
- upgrade (11 articles): upgrade-codeunit structure, upgrade-tag
  lifecycle and registration, protected DB reads, DataTransfer for
  large datasets, InitValue semantics, enum-ordinal preservation,
  obsolete-workflow, first-install detection.
- ui (9 articles): caption capitalization by phrase type, tooltip voice,
  teaching-tip vs tooltip, tour-tip conventions, character limits,
  banned terms, ampersand handling, title punctuation.
- style (11 articles): label-suffix convention, API page naming,
  temporary-variable prefix, label properties (Comment/Locked), named
  invocations, FieldCaption in user messages, OptionCaption pairing,
  Error-parameter passing, `this` keyword, required parentheses, file
  naming.

Gaps in existing domains:
- performance (11 articles): production-scale table catalog (no row
  counts, per internal-data concern), anti-false-positive for bounded
  tables, guard-before-Get ordering, redundant-Get-in-OnAfterGetRecord,
  LockTable in read-only helpers, combined ModifyAll passes, writes in
  OnAfterGetRecord, SetLoadFields heuristics, temporary-table
  regressions, FlowField source-table widening, MaintainSQLIndex
  disabling SIFT.
- security (2 articles): environment-specific hardcoded GUIDs,
  ValidateTableRelation=false on user input.

Intentionally excluded: specific production P95 row-count numbers
(aggregated internal telemetry); rewritten as categorical guidance on
which tables to treat as production-scale without publishing sizes.

All articles use `bc-version: [all]` (applies to every BC version, per
the new schema sentinel). Validator passes with 0 errors / 0 warnings.
2026-04-23 16:43:42 +02:00

1.7 KiB

bc-version domain keywords technologies countries application-area
all
performance
modifyall
bulk-update
filter
scan
recordset
al
w1
all

Combine multiple ModifyAll calls on the same recordset into a single pass

Description

ModifyAll(Field, Value) issues a SQL UPDATE against every row matching the record variable's current filters, setting one field. Calling it twice on the same filtered recordset — once per field to update — produces two separate UPDATE statements, each of which has to re-locate the matching rows through the index. On a ledger-entry-scale table with ten million rows and a filter that matches a thousand, the overhead is not a doubling of the update cost but a doubling of the more expensive row-location cost. A single FindSet(true) + set-by-set assignment + Modify(false) completes both field changes in one pass.

Best Practice

When more than one field needs to change on the same filtered recordset, iterate once with FindSet(true) and assign all fields per row. Reserve ModifyAll for the case where a single field change covers the whole update. If the filter set is truly huge and the trigger behaviour differs between fields, consider splitting with concrete evidence — otherwise the single-pass loop wins.

See sample: combine-multiple-modifyall-calls.good.al.

Anti Pattern

Applying SetRange against CustLedgerEntry on "Document No." and then calling ModifyAll("Accepted Payment Tolerance", ...) followed by ModifyAll("Accepted Pmt. Disc. Tolerance", false) — two scans over the same filtered rows. On Cust. Ledger Entry with production-scale data the redundant second scan is the dominant cost.

See sample: combine-multiple-modifyall-calls.bad.al.