Query()

This operation issues a query with a set of criteria and returns a list of records that exactly match the query.

Status Query(const QueryRequest& request, QueryResponse& response)

Request Syntax

auto request = QueryRequest()
    .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);

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.

RETURNS:

Status with QueryResponse

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;
}

auto request = milvus::QueryRequest()
                   .WithCollectionName(collection_name)
                   .AddPartitionName(partition_name)
                   .WithFilter(field_id + " in [1, 5, 10]")
                   .AddOutputField(field_id)
                   .AddOutputField(field_name)
                   .AddOutputField(field_age)
                   // set to EVENTUALLY level since the last query uses STRONG level and no data changed
                   .WithConsistencyLevel(milvus::ConsistencyLevel::EVENTUALLY);

std::cout << "\nQuery with expression: " << request.Filter() << std::endl;
milvus::QueryResponse response;
status = client->Query(request, response);
if (!status.IsOk()) {
    std::cout << status.Message() << std::endl;
}

auto query_results = response.Results();
milvus::EntityRows output_rows;
status = query_results.OutputRows(output_rows);
if (!status.IsOk()) {
    std::cout << status.Message() << std::endl;
}
std::cout << "Query results:" << std::endl;
for (const auto& row : output_rows) {
    std::cout << "\t" << row << std::endl;
}