IndexDesc

This class carries the parameters needed to build a vector or scalar index. Pass one or more IndexDesc objects to CreateIndexRequest::AddIndex(). DescribeIndex() also returns IndexDesc objects (via DescribeIndexResponse::Descs()) that include build-progress and state information.

IndexDesc();
IndexDesc(std::string field_name, std::string index_name,
          milvus::IndexType index_type,
          milvus::MetricType metric_type = milvus::MetricType::INVALID);

PARAMETERS:

• field_name (std::string)

  Name of the collection field to index.

• index_name (std::string)

  Optional name for the index. When empty, the server uses field_name as the index name. Must be unique within the collection.

• index_type (milvus::IndexType)

  The algorithm used to build the index. See IndexType for available values.

• metric_type (milvus::MetricType)

  Distance metric used to compare vectors. Not required for scalar field indexes. Default: MetricType::INVALID (server auto-determines). See MetricType for available values.

Methods

Input methods (used when creating an index):

• Status SetFieldName(std::string field_name) / const std::string& FieldName() const

  Sets or gets the field this index is built on.

• Status SetIndexName(std::string index_name) / const std::string& IndexName() const

  Sets or gets the index name. Cannot be empty after creation.

• Status SetIndexType(milvus::IndexType index_type) / milvus::IndexType IndexType() const

  Sets or gets the index algorithm.

• Status SetMetricType(milvus::MetricType metric_type) / milvus::MetricType MetricType() const

  Sets or gets the vector distance metric. Leave unset (or INVALID) for scalar field indexes.

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

  Adds an algorithm-specific tuning parameter (e.g., milvus::NLIST / "nlist" for IVF indexes, "M" and "efConstruction" for HNSW).

• const std::unordered_map<std::string, std::string>& ExtraParams() const

  Returns all extra parameters as a key-value map.

• Status ExtraParamsFromJson(std::string json)

  Populates extra parameters by parsing a JSON string.

Output methods (populated by DescribeIndex):

• int64_t IndexId() const

  Server-assigned index identifier.

• milvus::IndexStateCode StateCode() const

  Current build state: NONE, UNISSUED, IN_PROGRESS, FINISHED, or FAILED.

• std::string FailReason() const

  Failure message when StateCode() is FAILED.

• int64_t IndexedRows() const

  Number of rows that have been indexed. May exceed TotalRows() if compaction triggers re-indexing.

• int64_t TotalRows() const

  Total number of rows in the collection.

• int64_t PendingRows() const

  Number of rows not yet indexed.

Example

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

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

// Create an HNSW vector index and a scalar TRIE index together
IndexDesc index_vec("vec", "vec_idx", IndexType::HNSW, MetricType::COSINE);
index_vec.AddExtraParam("M", "16");
index_vec.AddExtraParam("efConstruction", "200");

IndexDesc index_name("name", "", IndexType::TRIE);

auto status = client->CreateIndex(
    CreateIndexRequest()
        .WithCollectionName("my_collection")
        .WithSync(true)
        .AddIndex(std::move(index_vec))
        .AddIndex(std::move(index_name)));

// Inspect build progress via DescribeIndex
DescribeIndexResponse resp;
client->DescribeIndex(
    DescribeIndexRequest()
        .WithCollectionName("my_collection")
        .WithIndexName("vec_idx"),
    resp);

for (const auto& desc : resp.Descs()) {
    std::cout << "IndexName:   " << desc.IndexName()   << "\n"
              << "IndexType:   " << std::to_string(desc.IndexType())  << "\n"
              << "State:       " << std::to_string(desc.StateCode())  << "\n"
              << "IndexedRows: " << desc.IndexedRows() << "\n"
              << "TotalRows:   " << desc.TotalRows()   << "\n";
}