Query modes

What a table can be asked, and what each mode costs to ask. A mode a table cannot answer is reported with a reason rather than returning nothing — a search that silently finds nothing looks exactly like a search that found nothing.

mode	needs	notes
scan	nothing	a filter and a page of rows
fts	an inverted index on a string column	uses the index; returns _score
vector	a vector column	uses an ANN index if one exists and the metric matches; otherwise scans every row. Returns _distance
hybrid	both of the above	two searches fused by rank, each leg costed separately

Access paths

Lance's plan says which path a query took, before it runs. These are the ones the console names:

operator	called	meaning
KNNVectorDistance	brute-force vector scan	Every row's vector is read and compared. Exact, and linear in table size.
ANNSubIndex	ANN index	An approximate index narrowed the candidates before distances were computed.
ANNIvfPartition	ANN index	An approximate index narrowed the candidates before distances were computed.
MatchQuery	inverted index	Full-text search used the inverted index rather than reading the column.
ScalarIndexQuery	scalar index	A scalar index answered part of the filter without reading the column.
MaterializeIndex	scalar index	A scalar index answered part of the filter without reading the column.

Limits

• a page returns at most 200 rows
• a search returns at most k = 200
• a request waits 30s by default, then stops waiting — Lance offers no way to interrupt a running scan, so the scan continues until it finishes

Heavy columns

Vectors, binary columns and Blob V2 columns are never read into a result. They are described from the schema, and no parameter of any query route can expand one.