issue: #44909
pr: #44917
When requery optimization is enabled, search results contain IDs but
empty FieldsData. During reduce/rerank operations, if the first shard
has empty FieldsData while others have data, PrepareResultFieldData
initializes an empty array, causing AppendFieldData to panic when
accessing array indices.
Changes:
- Find first non-empty FieldsData as template in 3 functions:
reduceAdvanceGroupBy, reduceSearchResultDataWithGroupBy,
reduceSearchResultDataNoGroupBy
- Add length check before 2 AppendFieldData calls in reduce functions to
prevent panic
- Improve newRerankOutputs to find first non-empty fieldData using
len(FieldsData) check instead of GetSizeOfIDs
- Add length check in appendResult before AppendFieldData
- Add comprehensive unit tests for empty and partial empty FieldsData
scenarios in both reduce and rerank functions
This fix handles both pure requery (all empty) and mixed scenarios (some
empty, some with data) without breaking normal search flow. The key
improvement is checking FieldsData length directly rather than IDs, as
requery may have IDs but empty FieldsData.
Signed-off-by: Wei Liu <wei.liu@zilliz.com>
