ConsistencyLevel

This enum controls the data-visibility guarantee for search and query operations. You can set the consistency level per-request via SearchRequest::WithConsistencyLevel(), QueryRequest::WithConsistencyLevel(), or as the collection default via CreateCollectionRequest::WithConsistencyLevel().

enum class ConsistencyLevel {
    NONE      = -1,
    STRONG    = 0,
    SESSION   = 1,
    BOUNDED   = 2,
    EVENTUALLY = 3,
};

VALUES:

• NONE (-1)

  No consistency level is specified for this request. The collection-level default is used.

• STRONG (0)

  All reads reflect the latest committed write. This is the strictest guarantee but may have higher latency because the query node must wait for the latest data to be replicated.

• SESSION (1)

  Within a single client session, reads always see writes made earlier in that same session. Writes from other sessions may not be immediately visible.

• BOUNDED (2)

  Reads may lag behind the latest write by a configurable time window (default 5 seconds). This balances freshness with throughput and is suitable for most production workloads.

• EVENTUALLY (3)

  No freshness guarantee. The query node returns results from whatever data it has locally. Offers the lowest latency at the cost of potentially stale results.

Example

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

// Per-request: require strong consistency for a critical query
QueryRequest query;
query.WithCollectionName("my_collection")
     .WithFilter("id in [1, 2, 3]")
     .AddOutputField("vec")
     .WithConsistencyLevel(ConsistencyLevel::STRONG);

// Per-request: accept bounded staleness for a high-throughput search
SearchRequest search;
search.WithCollectionName("my_collection")
      .WithAnnsField("vec")
      .WithLimit(10)
      .WithConsistencyLevel(ConsistencyLevel::BOUNDED);

// Collection-level default: set when creating the collection
auto status = client->CreateCollection(
    CreateCollectionRequest()
        .WithCollectionName("my_collection")
        .WithCollectionSchema(schema)
        .WithConsistencyLevel(ConsistencyLevel::BOUNDED));