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Basic ANN Search

Basic ANN Search

Based on an index file recording the sorted order of vector embeddings, the Approximate Nearest Neighbor (ANN) search locates a subset of vector embeddings based on the query vector carried in a received search request, compares the query vector with those in the subgroup, and returns the most similar results. With ANN search, Milvus provides an efficient search experience. This page helps you to learn how to conduct basic ANN searches.

Overview

The ANN and the k-Nearest Neighbors (kNN) search are the usual methods in vector similarity searches. In a kNN search, you must compare all vectors in a vector space with the query vector carried in the search request before figuring out the most similar ones, which is time-consuming and resource-intensive.

Unlike kNN searches, an ANN search algorithm asks for an index file that records the sorted order of vector embeddings. When a search request comes in, you can use the index file as a reference to quickly locate a subgroup probably containing vector embeddings most similar to the query vector. Then, you can use the specified metric type to measure the similarity between the query vector and those in the subgroup, sort the group members based on similarity to the query vector, and figure out the top-K group members.

ANN searches depend on pre-built indexes, and the search throughput, memory usage, and search correctness may vary with the index types you choose. You need to balance search performance and correctness.

To reduce the learning curve, Milvus provides AUTOINDEX. With AUTOINDEX, Milvus can analyze the data distribution within your collection while building the index and sets the most optimized index parameters based on the analysis to strike a balance between search performance and correctness.

For details on AUTOINDEX and applicable metric types, refer to AUTOINDEX and Metric Types. In this section, you will find detailed information about the following topics:

Single-vector search
Bulk-vector search
ANN search in partition
Use output fields
Use limit and offset
Enhancing ANN search

Single-Vector Search

In ANN searches, a single-vector search refers to a search that involves only one query vector. Based on the pre-built index and the metric type carried in the search request, Milvus will find the top-K vectors most similar to the query vector.

In this section, you will learn how to conduct a single-vector search. The code snippet assumes you have created a collection in a quick-setup manner. The search request carries a single query vector and asks Milvus to use Inner Product (IP) to calculate the similarity between query vectors and vectors in the collection and returns the three most similar ones.

Python Java Node.js Go cURL

from pymilvus import MilvusClient

client = MilvusClient(
    uri="http://localhost:19530",
    token="root:Milvus"
)

# 4. Single vector search
query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592]
res = client.search(
    collection_name="my_collection",
    anns_field="vector",
    data=[query_vector],
    limit=3,
    search_params={"metric_type": "IP"}
)

for hits in res:
    for hit in hits:
        print(hit)

# [
#     [
#         {
#             "id": 551,
#             "distance": 0.08821295201778412,
#             "entity": {}
#         },
#         {
#             "id": 296,
#             "distance": 0.0800950899720192,
#             "entity": {}
#         },
#         {
#             "id": 43,
#             "distance": 0.07794742286205292,
#             "entity": {}
#         }
#     ]
# ]

import io.milvus.v2.client.ConnectConfig;
import io.milvus.v2.client.MilvusClientV2;
import io.milvus.v2.service.vector.request.SearchReq;
import io.milvus.v2.service.vector.request.data.FloatVec;
import io.milvus.v2.service.vector.response.SearchResp;

import java.util.*;

MilvusClientV2 client = new MilvusClientV2(ConnectConfig.builder()
        .uri("http://localhost:19530")
        .token("root:Milvus")
        .build());
    
FloatVec queryVector = new FloatVec(new float[]{0.3580376395471989f, -0.6023495712049978f, 0.18414012509913835f, -0.26286205330961354f, 0.9029438446296592f});
SearchReq searchReq = SearchReq.builder()
        .collectionName("my_collection")
        .data(Collections.singletonList(queryVector))
        .topK(3)
        .build();

SearchResp searchResp = client.search(searchReq);

List<List<SearchResp.SearchResult>> searchResults = searchResp.getSearchResults();
for (List<SearchResp.SearchResult> results : searchResults) {
    System.out.println("TopK results:");
    for (SearchResp.SearchResult result : results) {
        System.out.println(result);
    }
}

// Output
// TopK results:
// SearchResp.SearchResult(entity={}, score=0.95944905, id=5)
// SearchResp.SearchResult(entity={}, score=0.8689616, id=1)
// SearchResp.SearchResult(entity={}, score=0.866088, id=7)

import (
    "context"
    "fmt"
    "log"

    "github.com/milvus-io/milvus/client/v2"
    "github.com/milvus-io/milvus/client/v2/entity"
)

func ExampleClient_Search_basic() {
    ctx, cancel := context.WithCancel(context.Background())
    defer cancel()

    milvusAddr := "127.0.0.1:19530"
    token := "root:Milvus"

    cli, err := client.New(ctx, &client.ClientConfig{
        Address: milvusAddr,
        APIKey:  token,
    })
    if err != nil {
        log.Fatal("failed to connect to milvus server: ", err.Error())
    }

    defer cli.Close(ctx)

    queryVector := []float32{0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592}

    resultSets, err := cli.Search(ctx, client.NewSearchOption(
        "my_collection", // collectionName
        3,             // limit
        []entity.Vector{entity.FloatVector(queryVector)},
    ))
    if err != nil {
        log.Fatal("failed to perform basic ANN search collection: ", err.Error())
    }

    for _, resultSet := range resultSets {
        log.Println("IDs: ", resultSet.IDs)
        log.Println("Scores: ", resultSet.Scores)
    }
    // Output:
    // IDs:
    // Scores:
}

import { MilvusClient, DataType } from "@zilliz/milvus2-sdk-node";

const address = "http://localhost:19530";
const token = "root:Milvus";
const client = new MilvusClient({address, token});

// 4. Single vector search
var query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592],

res = await client.search({
    collection_name: "my_collection",
    data: query_vector,
    limit: 3, // The number of results to return
})

console.log(res.results)

// [
//   { score: 0.08821295201778412, id: '551' },
//   { score: 0.0800950899720192, id: '296' },
//   { score: 0.07794742286205292, id: '43' }
// ]

export CLUSTER_ENDPOINT="http://localhost:19530"
export TOKEN="root:Milvus"

curl --request POST \
--url "${CLUSTER_ENDPOINT}/v2/vectordb/entities/search" \
--header "Authorization: Bearer ${TOKEN}" \
--header "Content-Type: application/json" \
-d '{
    "collectionName": "quick_setup",
    "data": [
        [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592]
    ],
    "annsField": "vector",
    "limit": 3
}'

# {
#     "code": 0,
#     "data": [
#         {
#             "distance": 0.08821295201778412,
#             "id": 551
#         },
#         {
#             "distance": 0.0800950899720192,
#             "id": 296
#         },
#         {
#             "distance": 0.07794742286205292,
#             "id": 43
#         }
#     ]
# }

Milvus ranks the search results by their similarity scores to the query vector in descending order. The similarity score is also termed the distance to the query vector, and its value ranges vary with the metric types in use.

The following table lists the applicable metric types and the corresponding distance ranges.

Metric Type	Characteristics	Distance Range
`L2`	A smaller value indicates a higher similarity.	[0, ∞)
`IP`	A greater value indicates a higher similarity.	[-1, 1]
`COSINE`	A greater value indicates a higher similarity.	[-1, 1]
`JACCARD`	A smaller value indicates a higher similarity.	[0, 1]
`HAMMING`	A smaller value indicates a higher similarity.	[0, dim(vector)]

Bulk-Vector Search

Similarly, you can include multiple query vectors in a search request. Milvus will conduct ANN searches for the query vectors in parallel and return two sets of results.

Python Java Node.js Go cURL

# 7. Search with multiple vectors
# 7.1. Prepare query vectors
query_vectors = [
    [0.041732933, 0.013779674, -0.027564144, -0.013061441, 0.009748648],
    [0.0039737443, 0.003020432, -0.0006188639, 0.03913546, -0.00089768134]
]

# 7.2. Start search
res = client.search(
    collection_name="my_collection",
    data=query_vectors,
    limit=3,
)

for hits in res:
    print("TopK results:")
    for hit in hits:
        print(hit)

# Output
#
# [
#     [
#         {
#             "id": 551,
#             "distance": 0.08821295201778412,
#             "entity": {}
#         },
#         {
#             "id": 296,
#             "distance": 0.0800950899720192,
#             "entity": {}
#         },
#         {
#             "id": 43,
#             "distance": 0.07794742286205292,
#             "entity": {}
#         }
#     ],
#     [
#         {
#             "id": 730,
#             "distance": 0.04431751370429993,
#             "entity": {}
#         },
#         {
#             "id": 333,
#             "distance": 0.04231833666563034,
#             "entity": {}
#         },
#         {
#             "id": 232,
#             "distance": 0.04221535101532936,
#             "entity": {}
#         }
#     ]
# ]

import io.milvus.v2.service.vector.request.SearchReq
import io.milvus.v2.service.vector.request.data.BaseVector;
import io.milvus.v2.service.vector.request.data.FloatVec;
import io.milvus.v2.service.vector.response.SearchResp

List<BaseVector> queryVectors = Arrays.asList(
        new FloatVec(new float[]{0.041732933f, 0.013779674f, -0.027564144f, -0.013061441f, 0.009748648f}),
        new FloatVec(new float[]{0.0039737443f, 0.003020432f, -0.0006188639f, 0.03913546f, -0.00089768134f})
);
SearchReq searchReq = SearchReq.builder()
        .collectionName("quick_setup")
        .data(queryVectors)
        .topK(3)
        .build();

SearchResp searchResp = client.search(searchReq);

List<List<SearchResp.SearchResult>> searchResults = searchResp.getSearchResults();
for (List<SearchResp.SearchResult> results : searchResults) {
    System.out.println("TopK results:");
    for (SearchResp.SearchResult result : results) {
        System.out.println(result);
    }
}

// Output
// TopK results:
// SearchResp.SearchResult(entity={}, score=0.49548206, id=1)
// SearchResp.SearchResult(entity={}, score=0.320147, id=3)
// SearchResp.SearchResult(entity={}, score=0.107413776, id=6)
// TopK results:
// SearchResp.SearchResult(entity={}, score=0.5678123, id=6)
// SearchResp.SearchResult(entity={}, score=0.32368967, id=2)
// SearchResp.SearchResult(entity={}, score=0.24108477, id=3)

// 7. Search with multiple vectors
const query_vectors = [
    [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592], 
    [0.19886812562848388, 0.06023560599112088, 0.6976963061752597, 0.2614474506242501, 0.838729485096104]
]

res = await client.search({
    collection_name: "quick_setup",
    vectors: query_vectors,
    limit: 5,
})

console.log(res.results)

// Output
// 
// [
//   [
//     { score: 0.08821295201778412, id: '551' },
//     { score: 0.0800950899720192, id: '296' },
//     { score: 0.07794742286205292, id: '43' }
//   ],
//   [
//     { score: 0.04431751370429993, id: '730' },
//     { score: 0.04231833666563034, id: '333' },
//     { score: 0.04221535101532936, id: '232' },
//   ]
// ]

export CLUSTER_ENDPOINT="http://localhost:19530"
export TOKEN="root:Milvus"

curl --request POST \
--url "${CLUSTER_ENDPOINT}/v2/vectordb/entities/search" \
--header "Authorization: Bearer ${TOKEN}" \
--header "Content-Type: application/json" \
-d '{
    "collectionName": "quick_setup",
    "data": [
        [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592],
        [0.19886812562848388, 0.06023560599112088, 0.6976963061752597, 0.2614474506242501, 0.838729485096104]
    ],
    "annsField": "vector",
    "limit": 3
}'

# {
#     "code": 0,
#     "data": [
#         [
#           {
#               "distance": 0.08821295201778412,
#               "id": 551
#           },
#           {
#               "distance": 0.0800950899720192,
#               "id": 296
#           },
#           {
#               "distance": 0.07794742286205292,
#               "id": 43
#           }
#         ],
#         [
#           {
#               "distance": 0.04431751370429993,
#               "id": 730
#           },
#           {
#               "distance": 0.04231833666563034,
#               "id": 333
#           },
#           {
#               "distance": 0.04221535101532936,
#               "id": 232
#           }
#        ]
#     ]
# }

ANN Search in Partition

Suppose you have created multiple partitions in a collection, and you can narrow the search scope to a specific number of partitions. In that case, you can include the target partition names in the search request to restrict the search scope within the specified partitions. Reducing the number of partitions involved in the search improves search performance.

The following code snippet assumes a partition named PartitionA in your collection.

Python Java Node.js Go cURL

# 4. Single vector search
query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592]
res = client.search(
    collection_name="my_collection",
    # highlight-next-line
    partition_names=["partitionA"],
    data=[query_vector],
    limit=3,
)

for hits in res:
    print("TopK results:")
    for hit in hits:
        print(hit)

# [
#     [
#         {
#             "id": 551,
#             "distance": 0.08821295201778412,
#             "entity": {}
#         },
#         {
#             "id": 296,
#             "distance": 0.0800950899720192,
#             "entity": {}
#         },
#         {
#             "id": 43,
#             "distance": 0.07794742286205292,
#             "entity": {}
#         }
#     ]
# ]

import io.milvus.v2.service.vector.request.SearchReq
import io.milvus.v2.service.vector.request.data.FloatVec;
import io.milvus.v2.service.vector.response.SearchResp

FloatVec queryVector = new FloatVec(new float[]{0.3580376395471989f, -0.6023495712049978f, 0.18414012509913835f, -0.26286205330961354f, 0.9029438446296592f});
SearchReq searchReq = SearchReq.builder()
        .collectionName("quick_setup")
        .partitionNames(Collections.singletonList("partitionA"))
        .data(Collections.singletonList(queryVector))
        .topK(3)
        .build();

SearchResp searchResp = client.search(searchReq);

List<List<SearchResp.SearchResult>> searchResults = searchResp.getSearchResults();
for (List<SearchResp.SearchResult> results : searchResults) {
    System.out.println("TopK results:");
    for (SearchResp.SearchResult result : results) {
        System.out.println(result);
    }
}

// Output
// TopK results:
// SearchResp.SearchResult(entity={}, score=0.6395302, id=13)
// SearchResp.SearchResult(entity={}, score=0.5408028, id=12)
// SearchResp.SearchResult(entity={}, score=0.49696884, id=17)

// 4. Single vector search
var query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592],

res = await client.search({
    collection_name: "quick_setup",
    // highlight-next-line
    partition_names: ["partitionA"],
    data: query_vector,
    limit: 3, // The number of results to return
})

console.log(res.results)

// [
//   { score: 0.08821295201778412, id: '551' },
//   { score: 0.0800950899720192, id: '296' },
//   { score: 0.07794742286205292, id: '43' }
// ]

export CLUSTER_ENDPOINT="http://localhost:19530"
export TOKEN="root:Milvus"

curl --request POST \
--url "${CLUSTER_ENDPOINT}/v2/vectordb/entities/search" \
--header "Authorization: Bearer ${TOKEN}" \
--header "Content-Type: application/json" \
-d '{
    "collectionName": "quick_setup",
    "partitionNames": ["partitionA"],
    "data": [
        [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592]
    ],
    "annsField": "vector",
    "limit": 3
}'

# {
#     "code": 0,
#     "data": [
#         {
#             "distance": 0.08821295201778412,
#             "id": 551
#         },
#         {
#             "distance": 0.0800950899720192,
#             "id": 296
#         },
#         {
#             "distance": 0.07794742286205292,
#             "id": 43
#         }
#     ]
# }

Use Output Fields

In a search result, Milvus includes the primary field values and similarity distances/scores of the entities that contain the top-K vector embeddings by default. You can include the target field names in a search request as the output fields to make the search results carry the values from other fields in these entities.

Python Java Node.js Go cURL

# 4. Single vector search
query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592],

res = client.search(
    collection_name="quick_setup",
    data=[query_vector],
    limit=3, # The number of results to return
    search_params={"metric_type": "IP"}，
    # highlight-next-line
    output_fields=["color"]
)

print(res)

# [
#     [
#         {
#             "id": 551,
#             "distance": 0.08821295201778412,
#             "entity": {
#                 "color": "orange_6781"
#             }
#         },
#         {
#             "id": 296,
#             "distance": 0.0800950899720192,
#             "entity": {
#                 "color": "red_4794"
#             }
#         },
#         {
#             "id": 43,
#             "distance": 0.07794742286205292,
#             "entity": {
#                 "color": "grey_8510"
#             }
#         }
#     ]
# ]

import io.milvus.v2.service.vector.request.SearchReq
import io.milvus.v2.service.vector.request.data.FloatVec;
import io.milvus.v2.service.vector.response.SearchResp

FloatVec queryVector = new FloatVec(new float[]{0.3580376395471989f, -0.6023495712049978f, 0.18414012509913835f, -0.26286205330961354f, 0.9029438446296592f});
SearchReq searchReq = SearchReq.builder()
        .collectionName("quick_setup")
        .data(Collections.singletonList(queryVector))
        .topK(3)
        .outputFields(Collections.singletonList("color"))
        .build();

SearchResp searchResp = client.search(searchReq);

List<List<SearchResp.SearchResult>> searchResults = searchResp.getSearchResults();
for (List<SearchResp.SearchResult> results : searchResults) {
    System.out.println("TopK results:");
    for (SearchResp.SearchResult result : results) {
        System.out.println(result);
    }
}

// Output
// TopK results:
// SearchResp.SearchResult(entity={color=black_9955}, score=0.95944905, id=5)
// SearchResp.SearchResult(entity={color=red_7319}, score=0.8689616, id=1)
// SearchResp.SearchResult(entity={color=white_5015}, score=0.866088, id=7)

// 4. Single vector search
var query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592],

res = await client.search({
    collection_name: "quick_setup",
    data: query_vector,
    limit: 3, // The number of results to return
    // highlight-next-line
    output_fields: ["color"]
})

console.log(res.results)

// [
//   { score: 0.08821295201778412, id: '551', entity: {"color": "orange_6781"}},
//   { score: 0.0800950899720192, id: '296' entity: {"color": "red_4794"}},
//   { score: 0.07794742286205292, id: '43' entity: {"color": "grey_8510"}}
// ]

export CLUSTER_ENDPOINT="http://localhost:19530"
export TOKEN="root:Milvus"

curl --request POST \
--url "${CLUSTER_ENDPOINT}/v2/vectordb/entities/search" \
--header "Authorization: Bearer ${TOKEN}" \
--header "Content-Type: application/json" \
-d '{
    "collectionName": "quick_setup",
    "data": [
        [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592]
    ],
    "annsField": "vector",
    "limit": 3,
    "outputFields": ["color"]
}'

# {
#     "code": 0,
#     "data": [
#         {
#             "distance": 0.08821295201778412,
#             "id": 551,
#             "color": "orange_6781"
#         },
#         {
#             "distance": 0.0800950899720192,
#             "id": 296,
#             "color": "red_4794"
#         },
#         {
#             "distance": 0.07794742286205292,
#             "id": 43
#             "color": "grey_8510"
#         }
#     ]
# }

Use Limit and Offset

You may notice that the parameter limit carried in the search requests determines the number of entities to include in the search results. This parameter specifies the maximum number of entities to return in a single search, and it is usually termed top-K.

If you wish to perform paginated queries, you can use a loop to send multiple Search requests, with the Limit and Offset parameters carried in each query request. Specifically, you can set the Limit parameter to the number of Entities you want to include in the current query results, and set the Offset to the total number of Entities that have already been returned.

The table below outlines how to set the Limit and Offset parameters for paginated queries when returning 100 Entities at a time.

Queries	Entities to return per query	Entities already been returned in total
The 1st query	100	0
The 2nd query	100	100
The 3rd query	100	200
The nth query	100	100 x (n-1)

Note that, the sum of limit and offset in a single ANN search should be less than 16,384.

Python Java Node.js Go cURL

# 4. Single vector search
query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592],

res = client.search(
    collection_name="quick_setup",
    data=[query_vector],
    limit=3, # The number of results to return
    search_params={
        "metric_type": "IP", 
        # highlight-next-line
        "offset": 10 # The records to skip
    }
)

import io.milvus.v2.service.vector.request.SearchReq
import io.milvus.v2.service.vector.request.data.FloatVec;
import io.milvus.v2.service.vector.response.SearchResp

FloatVec queryVector = new FloatVec(new float[]{0.3580376395471989f, -0.6023495712049978f, 0.18414012509913835f, -0.26286205330961354f, 0.9029438446296592f});
SearchReq searchReq = SearchReq.builder()
        .collectionName("quick_setup")
        .data(Collections.singletonList(queryVector))
        .topK(3)
        .offset(10)
        .build();

SearchResp searchResp = client.search(searchReq);

List<List<SearchResp.SearchResult>> searchResults = searchResp.getSearchResults();
for (List<SearchResp.SearchResult> results : searchResults) {
    System.out.println("TopK results:");
    for (SearchResp.SearchResult result : results) {
        System.out.println(result);
    }
}

// Output
// TopK results:
// SearchResp.SearchResult(entity={}, score=0.24120237, id=16)
// SearchResp.SearchResult(entity={}, score=0.22559784, id=9)
// SearchResp.SearchResult(entity={}, score=-0.09906838, id=2)

// 4. Single vector search
var query_vector = [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592],

res = await client.search({
    collection_name: "quick_setup",
    data: query_vector,
    limit: 3, // The number of results to return,
    // highlight-next-line
    offset: 10 // The record to skip.
})

export CLUSTER_ENDPOINT="http://localhost:19530"
export TOKEN="root:Milvus"

curl --request POST \
--url "${CLUSTER_ENDPOINT}/v2/vectordb/entities/search" \
--header "Authorization: Bearer ${TOKEN}" \
--header "Content-Type: application/json" \
-d '{
    "collectionName": "quick_setup",
    "data": [
        [0.3580376395471989, -0.6023495712049978, 0.18414012509913835, -0.26286205330961354, 0.9029438446296592]
    ],
    "annsField": "vector",
    "limit": 3,
    "offset": 10
}'

Enhancing ANN Search

AUTOINDEX considerably flattens the learning curve of ANN searches. However, the search results may not always be correct as the top-K increases. By reducing the search scope, improving search result relevancy, and diversifying the search results, Milvus works out the following search enhancements.

Filtered Search

You can include filtering conditions in a search request so that Milvus conducts metadata filtering before conducting ANN searches, reducing the search scope from the whole collection to only the entities matching the specified filtering conditions.

For more about metadata filtering and filtering conditions, refer to Filtered Search and Metadata Filtering.
Range Search

You can improve search result relevancy by restricting the distance or score of the returned entities within a specific range. In Milvus, a range search involves drawing two concentric circles with the vector embedding most similar to the query vector as the center. The search request specifies the radius of both circles, and Milvus returns all vector embeddings that fall within the outer circle but not the inner circle.

For more about range search, refer to Range Search.
Grouping Search

If the returned entities hold the same value in a specific field, the search results may not represent the distribution of all vector embeddings in the vector space. To diversify the search results, consider using the grouping search.

For more about grouping search, refer to Grouping Search,
Hybrid Search

A collection can include up to four vector fields to save the vector embeddings generated using different embedding models. By doing so, you can use a hybrid search to rerank the search results from these vector fields, improving the recall rate.

For more about hybrid search, refer to Hybrid Search.
Search Iterator

A single ANN search returns a maximum of 16,384 entities. Consider using search iterators if you need more entities to return in a single search.

For details on search iterators, refer to Search Iterator.
Full-Text Search

Full text search is a feature that retrieves documents containing specific terms or phrases in text datasets, then ranking the results based on relevance. This feature overcomes semantic search limitations, which might overlook precise terms, ensuring you receive the most accurate and contextually relevant results. Additionally, it simplifies vector searches by accepting raw text input, automatically converting your text data into sparse embeddings without the need to manually generate vector embeddings.

For details on full-text search, refer to Full Text Search.
Text Match

Text match in Milvus enables precise document retrieval based on specific terms. This feature is primarily used for filtered search to satisfy specific conditions and can incorporate scalar filtering to refine query results, allowing similarity searches within vectors that meet scalar criteria.

For details on text match, refer to Text Match.
Use Partition Key

Involving multiple scalar fields in metadata filtering and using a rather complicated filtering condition may affect search efficiency. Once you set a scalar field as the partition key and use a filtering condition involving the partition key in the search request, it can help restrict the search scope within the partitions corresponding to the specified partition key values.

For details on the partition key, refer to Use Partition Key.
Use mmap

In Milvus, memory-mapped files allow for direct mapping of file contents into memory. This feature enhances memory efficiency, particularly in situations where available memory is scarce but complete data loading is infeasible. This optimization mechanism can increase data capacity while ensuring performance up to a certain limit; however, when the amount of data exceeds memory by too much, search and query performance may suffer serious degradation, so please choose to turn this feature on or off as appropriate.

For details on mmap-settings, refer to Use mmap.
Clustering Compaction

Clustering compaction is designed to improve search performance and reduce costs in large collections. This guide will help you understand clustering compaction and how this feature can improve search performance.

For details on clustering compactions, refer to Clustering Compaction.

Basic ANN Search
Overview
Single-Vector Search
Bulk-Vector Search
ANN Search in Partition
Use Output Fields
Use Limit and Offset
Enhancing ANN Search

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Basic ANN Search

Overview

Single-Vector Search

Bulk-Vector Search

ANN Search in Partition

Use Output Fields

Use Limit and Offset

Enhancing ANN Search

Table of contents

Try Managed Milvus for Free

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