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. You should create an index before you can load a collection.

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());

curl -X 'POST' \
  'http://localhost:9091/api/v1/collection/load' \
  -H 'accept: application/json' \
  -H 'Content-Type: application/json' \
  -d '{
    "collection_name": "book"
  }'

{}

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)

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