bcquality/microsoft/knowledge/upgrade/initvalue-does-not-update-existing-rows.md
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2026-09-09 17:25:29 +02:00

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upgrade
initvalue
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table-extension
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InitValue does not back-fill existing rows

Description

InitValue on a field defines the value the platform assigns when a new record is inserted. It does not touch rows that already exist when the field is added. When a new field is added to an existing table — directly or via a table extension — every pre-existing row receives the datatype default (false for Boolean, 0 for numeric, empty for text), not the InitValue. If the intended semantics require existing rows to carry the InitValue, the change is incomplete without an upgrade routine that sets the field on those rows.

Several legitimate cases do NOT need upgrade code:

  • New fields on brand-new tables (no existing rows).
  • New Boolean fields without InitValue where the datatype default false is the intended value.
  • New fields on configuration / setup tables that have no meaningful "existing data".
  • Informational or optional fields (logging, preferences, tracking) where false / empty is a valid state.

Best Practice

When a new field on an existing table has an InitValue that matters, ship an upgrade procedure that walks the existing rows and sets the field to the same value — typically via DataTransfer.AddConstantValue for performance — guarded by an upgrade tag.

See sample: initvalue-does-not-update-existing-rows.good.al.

Anti Pattern

Adding a field with InitValue = true; (or any non-default InitValue) and shipping no upgrade code. Existing rows silently carry the datatype default, leaving the table in two states: rows created before the upgrade with the wrong value, and rows created after with the right one.

See sample: initvalue-does-not-update-existing-rows.bad.al.