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Skip reading a chunk's vectors when the KNN filters keep none of its rows #330

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Skip reading a chunk's vectors when the KNN filters keep none of its rows #330

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77 changes: 46 additions & 31 deletions sqlite-vec.c
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Original file line number Diff line number Diff line change
Expand Up @@ -6498,6 +6498,16 @@ void bitmap_fill(u8 *bitmap, i32 n) {
memset(bitmap, 0xFF, n / CHAR_BIT);
}

int bitmap_any(u8 *bitmap, i32 n) {
assert((n % 8) == 0);
for (int i = 0; i < n / CHAR_BIT; i++) {
if (bitmap[i]) {
return 1;
}
}
return 0;
}

/**
* @brief Finds the minimum k items in distances, and writes the indicies to
* out.
Expand Down Expand Up @@ -7400,37 +7410,6 @@ int vec0Filter_knn_chunks_iter(vec0_vtab *p, sqlite3_stmt *stmtChunks,
goto cleanup;
}

// open the vector chunk blob for the current chunk
rc = sqlite3_blob_open(p->db, p->schemaName,
p->shadowVectorChunksNames[vectorColumnIdx],
"vectors", chunk_id, 0, &blobVectors);
if (rc != SQLITE_OK) {
vtab_set_error(&p->base, "could not open vectors blob for chunk %lld",
chunk_id);
rc = SQLITE_ERROR;
goto cleanup;
}

i64 currentBaseVectorsSize = sqlite3_blob_bytes(blobVectors);
i64 expectedBaseVectorsSize =
p->chunk_size * vector_column_byte_size(*vector_column);
if (currentBaseVectorsSize != expectedBaseVectorsSize) {
// IMP: V16465_00535
vtab_set_error(
&p->base,
"vectors blob size doesn't match - expected %lld, found %lld",
expectedBaseVectorsSize, currentBaseVectorsSize);
rc = SQLITE_ERROR;
goto cleanup;
}
rc = sqlite3_blob_read(blobVectors, baseVectors, currentBaseVectorsSize, 0);

if (rc != SQLITE_OK) {
vtab_set_error(&p->base, "vectors blob read error for %lld", chunk_id);
rc = SQLITE_ERROR;
goto cleanup;
}

bitmap_copy(b, chunkValidity, p->chunk_size);
if (arrayRowidsIn) {
bitmap_clear(bmRowids, p->chunk_size);
Expand Down Expand Up @@ -7477,6 +7456,42 @@ int vec0Filter_knn_chunks_iter(vec0_vtab *p, sqlite3_stmt *stmtChunks,
}
}

// A chunk whose rowid and metadata filters keep no row offers no
// candidate, so its vectors are never read.
if (!bitmap_any(b, p->chunk_size)) {
continue;
}

// open the vector chunk blob for the current chunk
rc = sqlite3_blob_open(p->db, p->schemaName,
p->shadowVectorChunksNames[vectorColumnIdx],
"vectors", chunk_id, 0, &blobVectors);
if (rc != SQLITE_OK) {
vtab_set_error(&p->base, "could not open vectors blob for chunk %lld",
chunk_id);
rc = SQLITE_ERROR;
goto cleanup;
}

i64 currentBaseVectorsSize = sqlite3_blob_bytes(blobVectors);
i64 expectedBaseVectorsSize =
p->chunk_size * vector_column_byte_size(*vector_column);
if (currentBaseVectorsSize != expectedBaseVectorsSize) {
// IMP: V16465_00535
vtab_set_error(
&p->base,
"vectors blob size doesn't match - expected %lld, found %lld",
expectedBaseVectorsSize, currentBaseVectorsSize);
rc = SQLITE_ERROR;
goto cleanup;
}
rc = sqlite3_blob_read(blobVectors, baseVectors, currentBaseVectorsSize, 0);

if (rc != SQLITE_OK) {
vtab_set_error(&p->base, "vectors blob read error for %lld", chunk_id);
rc = SQLITE_ERROR;
goto cleanup;
}

for (int i = 0; i < p->chunk_size; i++) {
if (!bitmap_get(b, i)) {
Expand Down