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hrColumnDuplicate
Where the operation crossed the contract
hrColumnDuplicate means column creation reused a name already defined in the table.
This is the legacy Directory Service backup/restore HRESULT form of JET_errColumnDuplicate (0xC80005E4).
The key comparison is: hrObjectDuplicate is namespace-generic; this code isolates a column collision. The first useful observation is to enumerate column metadata and compare type, flags, code page, and maximum length with the desired definition. This evidence separates schema definition, row-size accounting, null semantics, multivalue selection, and stale column IDs.
Reconstruct the engine state
- Code-specific observation: enumerate column metadata and compare type, flags, code page, and maximum length with the desired definition.
- JET_COLUMNDEF fields, flags, code page, maximum length, and column ID origin; associate it with this result rather than with a later generic exception.
- the encoded value length, null/empty state, and itag sequence; associate it with this result rather than with a later generic exception.
- the complete row-size contribution from fixed, variable, tagged, and long-value data.
The ESE objects in play
| Diagnostic layer | column schema, row-size accounting, tagged/multivalued storage, and column identifiers |
|---|---|
| Typical API surface | JetAddColumn, JetDeleteColumn, JetSetColumn, JetRetrieveColumn, and JET_COLUMNDEF |
| Code-specific condition | column creation reused a name already defined in the table |
| First corrective direction | make the migration idempotent only when the existing definition is semantically identical |
Column IDs are metadata scoped to a table and should be refreshed after schema changes. Null, zero-length, deletion, and missing multivalue instances are distinct states.
Repair without destroying evidence
- Freeze the failing request context and record
0xC80005E4, the Jet API name, and the current instance/session ownership. - Verify the code-specific precondition: enumerate column metadata and compare type, flags, code page, and maximum length with the desired definition.
- Apply the targeted fix: make the migration idempotent only when the existing definition is semantically identical.
- Before retrying the operation, reconcile column metadata, row layout, and the exact stored value state.
Do not collapse these codes together
hrColumnDoesNotFit | the field update cannot fit in the current record layout and remaining row budget |
|---|---|
hrColumnInUse | a schema change targets a column that an index or other active definition still depends on |
hrColumnCannotIndex | the selected long-value or otherwise unsupported column cannot participate in an index key |
Actions that can hide or worsen the problem
- Do not alter the column schema in place without a migration and rollback plan.
- Do not collapse null, zero-length data, missing value, and tagged-value deletion into one state.
Technical references
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