Iterator

This page documents both SearchIterator and QueryIterator. Both are type aliases of the Iterator<T> template base class, where T is SingleResult for search and QueryResults for query. Use these iterators when you need to retrieve more results than the limit of a single request allows.

Iterator

Abstract base class. Not instantiated directly; use the concrete aliases below.

template <typename T>
class Iterator {
 public:
    virtual Status Next(T& results) = 0;
};

• virtual Status Next(T& results) = 0

  Fetches the next batch of results into results. Returns a Status with IsOk() == false when there are no more results (the iterator is exhausted). Not thread-safe.

SearchIterator

Iterates over SingleResult batches from a SearchIterator() call. Each call to Next() fills a SingleResult with the next batch of hits.

using SearchIterator    = Iterator<SingleResult>;
using SearchIteratorPtr = std::shared_ptr<SearchIterator>;

Obtained via MilvusClientV2::SearchIterator(IteratorArguments, SearchIteratorPtr&).

QueryIterator

Iterates over QueryResults batches from a QueryIterator() call. Each call to Next() fills a QueryResults with the next batch of rows.

using QueryIterator    = Iterator<QueryResults>;
using QueryIteratorPtr = std::shared_ptr<QueryIterator>;

Obtained via MilvusClientV2::QueryIterator(IteratorArguments, QueryIteratorPtr&).

Example

#include <milvus/MilvusClientV2.h>
using namespace milvus;

auto client = MilvusClientV2::Create();
client->Connect(ConnectParam("http://localhost:19530").WithToken("root:Milvus"));

// Query iterator — page through all rows
QueryIteratorPtr query_iter;
auto status = client->QueryIterator(
    IteratorArguments()
        .WithCollectionName("my_collection")
        .WithFilter("id >= 0")
        .AddOutputField("id")
        .WithBatchSize(100),
    query_iter);
if (!status.IsOk()) {
    std::cout << status.Message() << std::endl;
}

int64_t total = 0;
while (true) {
    QueryResults batch;
    status = query_iter->Next(batch);
    if (!status.IsOk()) break;   // exhausted or error
    total += static_cast<int64_t>(batch.GetRowCount());
}
std::cout << "Total rows retrieved: " << total << "\n";

// Search iterator — page through top-k results
SearchIteratorPtr search_iter;
status = client->SearchIterator(
    IteratorArguments()
        .WithCollectionName("my_collection")
        .WithAnnsField("vec")
        .WithBatchSize(50)
        .AddFloatVector(std::vector<float>(128, 0.1f)),
    search_iter);
if (!status.IsOk()) {
    std::cout << status.Message() << std::endl;
}

while (true) {
    SingleResult batch;
    status = search_iter->Next(batch);
    if (!status.IsOk()) break;
    std::cout << "Batch hits: " << batch.GetRowCount() << "\n";
}