QueryIterator()

This operation returns a QueryIterator object based on scalar field(s) by filtering expression.

Status QueryIterator(QueryIteratorRequest& request, QueryIteratorPtr& response)

Request Syntax

auto request = QueryIteratorRequest()
    .WithDatabaseName(db_name)
    .WithCollectionName(collection_name)
    .WithPartitionNames(partition_names)
    .WithOutputFields(output_field_names)
    .WithConsistencyLevel(consistency_level)
    .WithFilter(filter)
    .WithFilterTemplates(value)
    .WithLimit(limit)
    .WithOffset(offset)
    .WithIgnoreGrowing(ignore_growing)
    .WithTimezone(timezone)
    .WithReduceStopForBest(reduce_stop_for_best);

REQUEST METHODS:

• WithDatabaseName(const std::string& db_name)

  Sets the target database name. The default database applies if it is empty.

• WithCollectionName(const std::string& collection_name)

  Sets the name of the collection.

• WithPartitionNames(std::set<std::string>&& partition_names)

  Sets the names of the partitions. If it is empty, the default partition applies.

• AddPartitionName(const std::string& partition_name)

  Adds a partition name.

• WithOutputFields(std::set<std::string>&& output_field_names)

  Sets the output field names.

• AddOutputField(const std::string& output_field)

  Adds an output field.

• WithConsistencyLevel(ConsistencyLevel consistency_level)

  Sets the consistency level.

• WithFilter(std::string filter)

  Sets a filter expression.

• AddFilterTemplate(std::string key, const nlohmann::json& filter_template)

  Adds a filter template. This takes effect only if WithFilter() is set. Read this page for more about filter templating.

• WithFilterTemplates(std::unordered_map<std::string, nlohmann::json>&& filter_templates)

  Sets filter templates. This takes effect only if WithFilter() is set. Read this page for more about filter templating.

• WithLimit(int64_t limit)

  Sets the number of entities to return. This is available only when the filter expression is empty.

• WithOffset(int64_t offset)

  Sets the offset value. This is available only when the filter expression is empty.

• WithIgnoreGrowing(bool ignore_growing)

  Sets whether to ignore growing segments.

• AddExtraParam(const std::string& key, const std::string& value)

  Add an extra param.

• WithTimezone(const std::string& timezone)

  Sets the timezone. This applies only to the Timestamptz field. For details, refer to this page.

• WithReduceStopForBest(bool reduce_stop_for_best)

  Sets the flag of internal retrieve strategy.

RETURNS:

Status with QueryIteratorPtr

Check status.IsOk() to confirm success.

EXCEPTIONS:

• StatusCode

  Check status.Code() and status.Message() for error details.

Example

#include "milvus/MilvusClientV2.h"
auto client = milvus::MilvusClientV2::Create();

milvus::ConnectParam connect_param{"http://localhost:19530", "root:Milvus"};
auto status = client->Connect(connect_param);
if (!status.IsOk()) {
    std::cout << status.Message() << std::endl;
}

milvus::QueryIteratorRequest request;
request.SetCollectionName(collection_name);
request.SetBatchSize(batch);
request.SetOffset(offset);
request.SetLimit(limit);
request.SetFilter(filter);
request.AddOutputField(field_name);
request.AddOutputField(field_age);
request.AddOutputField("a");  // dynamic field

milvus::QueryIteratorPtr iterator;
status = client->QueryIterator(request, iterator);
if (!status.IsOk()) {
    std::cout << status.Message() << std::endl;
}

std::set<int64_t> ids;
int pages = 0;
uint64_t total_count = 0;
while (true) {
    milvus::QueryResults batch_results;
    status = iterator->Next(batch_results);
    if (!status.IsOk()) {
        std::cout << status.Message() << std::endl;
    }
    auto batch_count = batch_results.GetRowCount();
    if (batch_count == 0) {
        std::cout << "query iteration finished" << std::endl;
        break;
    }
    pages++;
    total_count += batch_count;

    milvus::EntityRows rows;
    status = batch_results.OutputRows(rows);
    if (!status.IsOk()) {
    std::cout << status.Message() << std::endl;
}
    std::cout << "No." << std::to_string(pages) << " page " << std::to_string(rows.size()) << " rows fetched"
              << std::endl;
    std::cout << "\tthe first row: " << (*rows.begin()).dump() << std::endl;
    std::cout << "\tthe last row: " << (*rows.rbegin()).dump() << std::endl;
    for (const auto& row : rows) {
        // std::cout << row.dump() << std::endl;
        ids.insert(row[field_id].get<int64_t>());
    }
}