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dc14e7bb2a
- performance/use-setloadfields-for-partial-records: Clarify that filter-only fields (SetRange/SetFilter) do not need to be listed in SetLoadFields — the DB resolves them via the index without hydrating the value into AL memory. - performance/avoid-calcfields-in-loops: Add explicit exception for OnAfterGetRecord and OnValidate triggers, which are platform-managed and not developer-authored loops. - performance/split-read-only-and-write-paths-to-avoid-locktable: Add ReadIsolation as the primary recommendation for read-only paths; LockTable reserved for confirmed write paths only. - performance/prefer-direct-record-over-recordref: Scope the finding to hot unbounded loops (10k+ rows) over ledger-entry-scale tables; RecordRef in bounded/admin/setup contexts is not a concern. - upgrade/enum-changes-must-be-additive-at-the-end: Replace direct ObsoleteState = Removed guidance with the two-stage workflow (Pending first, Removed later); reference use-obsolete-pending-before-removed. - upgrade/use-datatransfer-for-large-dataset-initialization: Add the >300,000 records threshold as the concrete trigger for requiring DataTransfer. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
28 lines
1.9 KiB
Markdown
28 lines
1.9 KiB
Markdown
---
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bc-version: [all]
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domain: upgrade
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keywords: [datatransfer, initvalue, large-dataset, bulk-update, upgrade]
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technologies: [al]
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countries: [w1]
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application-area: [all]
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---
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# Use DataTransfer to initialize large tables in upgrade; not FindSet plus Modify
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## Description
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An upgrade that populates a new field on millions of existing rows with a FindSet+Modify loop pays a round-trip and a per-row trigger invocation for every row — turning a multi-hour upgrade into a multi-day one on ledger-entry-scale tables. `DataTransfer` pushes the update to SQL as a single set-based operation using source filters and constant values, which is the supported platform mechanism for this scenario. The tradeoff: DataTransfer bypasses validation triggers and event subscribers — if the step depends on trigger logic, that has to be reconstructed explicitly.
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## Best Practice
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Use DataTransfer when initializing a new field on an existing table that **can contain more than 300,000 records**, or whenever a new field is added to an existing table and the initialization must run across all existing rows. Tables in the ledger-entry and document-line category reliably exceed this threshold; treat them as requiring DataTransfer by default.
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Set tables, add source filters, add constant values, call CopyFields, clear, and repeat for additional slices. When trigger or subscriber behaviour is required, do that work separately against a filtered result set so the bulk update remains set-based.
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See sample: `use-datatransfer-for-large-dataset-initialization.good.al`.
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## Anti Pattern
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`FindSet(true)` + `Modify()` in a loop as the initialization path for a new field across an entire existing table. The resulting upgrade time is proportional to the row count; for a ten-million-row ledger-entry table it is the single largest step in the release.
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See sample: `use-datatransfer-for-large-dataset-initialization.bad.al`.
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