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hrFLDKeyTooBig
The exact condition reported here
hrFLDKeyTooBig means an index key exceeded the legacy key budget and was truncated rather than represented in full.
The stored value is 0x88000190 (positive JET status 400; 400). The HRESULT carries a warning, so the call may have useful output or a valid cursor state that must be inspected. The legacy symbolic name comes from the Windows Directory Service backup/restore message header.
The first useful distinction is that this warning differs from a hard key-size error because the operation may continue with a shortened key. Start by logging the index definition, normalized key bytes, contributing columns, locale, and whether truncation can merge otherwise distinct values.
Objects and state involved
| Diagnostic layer | index key construction, NULL semantics, and legacy key limits |
|---|---|
| Relevant API surface | index definition, key creation, seeks, ranges, and record updates that change indexed values |
| Code-specific condition | an index key exceeded the legacy key budget and was truncated rather than represented in full |
| Narrow corrective direction | redesign the key or explicitly validate truncation semantics before relying on exact uniqueness or seek behavior |
An index key is derived data whose byte representation depends on schema, locale, and column values. A warning can leave a usable cursor or index entry while changing exact-match or uniqueness assumptions.
Adjacent conditions
This result specifically means that this warning differs from a hard key-size error because the operation may continue with a shortened key. Related values below can appear in the same workflow but require a different response:
hrFLDNullKey | key construction produced a NULL key for the current record or index expression |
|---|---|
hrInvalidRecips | the recipient information supplied to the legacy backup operation failed validation |
hrLogFileCorrupt | ESE detected structural or checksum corruption while reading a transaction log |
Diagnostic record
- Code-specific observation: log the index definition, normalized key bytes, contributing columns, locale, and whether truncation can merge otherwise distinct values.
- NULL and conditional-index rules: capture the value and timestamp from the first occurrence.
- Seek or insert result: capture the value and timestamp from the first occurrence.
- Index definition and segment order: capture the value and timestamp from the first occurrence.
- Normalized key length and bytes: capture the value and timestamp from the first occurrence.
Actions that can make diagnosis worse
- Do not compare only the source text when the stored key is normalized or truncated.
- Do not collapse NULL and empty values in diagnostics.
Corrective path
- Record it,
0x88000190, the API name, the current phase, and all live context or file owners. - Verify the condition by logging the index definition, normalized key bytes, contributing columns, locale, and whether truncation can merge otherwise distinct values.
- Apply only the targeted fix: redesign the key or explicitly validate truncation semantics before relying on exact uniqueness or seek behavior.
Acceptance criteria for a fix
A useful regression test should force the condition “an index key exceeded the legacy key budget and was truncated rather than represented in full”, call one documented API transition, and assert the exact HRESULT.
Technical references
- ESE warnings and errors — API ordering, file semantics, warning/error interpretation, or recovery behavior relevant to this HRESULT.
- JET_ERR enumeration
- Open-source ESE implementation
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