Load a Collection

This topic describes how to load the collection to memory before a search or a query. All search and query operations within Milvus are executed in memory.

Milvus allows users to load a collection as multiple replicas to utilize the CPU and memory resources of extra query nodes. This feature boosts the overall QPS and throughput without extra hardware. Before loading a collection, ensure that you have already indexed it.

from pymilvus import Collection, utility

# Get an existing collection.
collection = Collection("book")      
collection.load(replica_number=2)

# Check the loading progress and loading status
utility.load_state("book")
# Output: <LoadState: Loaded>

utility.loading_progress("book")
# Output: {'loading_progress': 100%}

await milvusClient.loadCollection({
  collection_name: "book",
});

err := milvusClient.LoadCollection(
  context.Background(),   // ctx
  "book",                 // CollectionName
  false                   // async
)
if err != nil {
  log.Fatal("failed to load collection:", err.Error())
}

// To get the load status
loadStatus, err := milvusClient.GetLoadState(
  context.Background(),             // ctx
  "book",                           // CollectionName
  []string{"Default partition"}     // List of partitions
)
if err != nil {
    log.Fatal("failed to get the load state", err.Error())
}

// To get the loading progress
percentage, err := milvusClient.GetLoadingProgress(
    context.Background(),           // ctx
    "book",                         // CollectionName
    []string{"Default partition"}   // List of partitions
)
if err != nil {
    log.Fatal("failed to get the loading progress", err.Error())
}

milvusClient.loadCollection(
  LoadCollectionParam.newBuilder()
    .withCollectionName("book")
    .build()
);

// You can check the loading status 

GetLoadStateParam param = GetLoadStateParam.newBuilder()
        .withCollectionName(collectionName)
        .build();
R<GetLoadStateResponse> response = client.getLoadState(param);
if (response.getStatus() != R.Status.Success.getCode()) {
    System.out.println(response.getMessage());
}
System.out.println(response.getState());

// and loading progress as well

GetLoadingProgressParam param = GetLoadingProgressParam.newBuilder()
        .withCollectionName(collectionName)
        .build();
R<GetLoadingProgressResponse> response = client.getLoadingProgress(param);
if (response.getStatus() != R.Status.Success.getCode()) {
    System.out.println(response.getMessage());
}
System.out.println(response.getProgress());

var collection = Client.GetCollection("book")
await collection.LoadAsync();

// You can check the loading progress

var progress = await collection.GetLoadingProgressAysnc();
Console.WriteLine(progress);

Parameter	Description
partition_name (optional)	Name of the partition to load.
replica_number (optional)	Number of the replica to load.

Parameter	Description
collection_name	Name of the collection to load.

Parameter	Description
ctx	Context to control API invocation process.
CollectionName	Name of the collection to load.
async	Switch to control sync/async behavior. The deadline of context is not applied in sync load.

Parameter	Description
CollectionName	Name of the collection to load.

Option	Description
(Optional) replicaNumber	The name of the partition to load.

Get replica information

You can check the information of the loaded replicas.

from pymilvus import Collection
collection = Collection("book")      # Get an existing collection.
collection.load(replica_number=2)    # Load collection as 2 replicas
result = collection.get_replicas()
print(result)

GetReplicasParam getReplicasParam = GetReplicasParam.newBuilder()
    .withCollectionName("book")
    .build();

client.getReplicas(getReplicasParam);

replicas, err = client.GetReplicas(context.Background(), "book")

let res = client.getReplicas({
    collectionID: '436777253933154305' // should be a collection id returned by a compact task.
})

Below is an example of the output.

Replica groups:
- Group: <group_id:435309823872729305>, <group_nodes:(21, 20)>, <shards:[Shard: <channel_name:milvus-zong-rootcoord-dml_27_435367661874184193v0>, <shard_leader:21>, <shard_nodes:[21]>, Shard: <channel_name:milvus-zong-rootcoord-dml_28_435367661874184193v1>, <shard_leader:20>, <shard_nodes:[20, 21]>]>
- Group: <group_id:435309823872729304>, <group_nodes:(25,)>, <shards:[Shard: <channel_name:milvus-zong-rootcoord-dml_28_435367661874184193v1>, <shard_leader:25>, <shard_nodes:[25]>, Shard: <channel_name:milvus-zong-rootcoord-dml_27_435367661874184193v0>, <shard_leader:25>, <shard_nodes:[25]>]>

Constraints

• Error will be returned at the attempt to load partition(s) when the parent collection is already loaded. Future releases will support releasing partitions from a loaded collection, and (if needed) then loading some other partition(s).
• "Load successfully" will be returned at the attempt to load the collection that is already loaded.
• Error will be returned at the attempt to load the collection when the child partition(s) is/are already loaded. Future releases will support loading the collection when some of its partitions are already loaded.
• Loading different partitions in a same collection via separate RPCs is not allowed.

What's next

• Learn more basic operations of Milvus:
  • Insert data into Milvus
  • Create a partition
  • Build an index for vectors
  • Conduct a vector search
  • Conduct a hybrid search