QueryIterator

This operation creates a query iterator that retrieves matching entities from a collection in batches. Use this for large result sets that should not be loaded into memory all at once.

go

func (c *Client) QueryIterator(ctx context.Context, option QueryIteratorOption, callOptions ...grpc.CallOption) (QueryIterator, error)

Request Syntax

Creates the request for QueryIterator().

go

client.QueryIterator(ctx, milvusclient.NewQueryIteratorOption(collectionName).
    WithBatchSize(batchSize).
    WithPartitions(partitionNames...).
    WithFilter(expr).
    WithOutputFields(fieldNames...).
    WithConsistencyLevel(consistencyLevel).
    WithIteratorLimit(limit),
)

PARAMETERS:

• collectionName (string) -

  [REQUIRED]

  The name of the collection to query.

BUILDER METHODS:

• NewQueryIteratorOption(collectionName string)

  Creates a new query iterator option for the specified collection.

• WithBatchSize(batchSize int)

  The number of entities to return per iteration batch. Default: 1000.

• WithPartitions(partitionNames ...string)

  The partitions to query. If not specified, all partitions are queried.

• WithNamespace(namespace string)

  Scopes the query iterator to a collection namespace.

• WithFilter(expr string)

  A boolean expression to filter entities. Only entities matching the expression are returned.

• WithOutputFields(fieldNames ...string)

  The fields to include in the returned entities. If not specified, only the primary key field is returned.

• WithConsistencyLevel(consistencyLevel entity.ConsistencyLevel)

  The consistency level for the query. Default: Bounded.

• WithIteratorLimit(limit int64)

  The maximum total number of entities to iterate over. A negative value means unlimited. Default: Unlimited (-1).

RETURN TYPE:

*QueryIterator, error

RETURNS:

QueryIterator, error The QueryIterator interface provides paginated access to query results. Call Next() repeatedly until io.EOF is returned.

PARAMETERS:

• result (*QueryIterator) -

  The *QueryIterator value returned by QueryIterator().

ERROR HANDLING:

• error

  The operation fails. The specified collection does not exist, invalid parameters, or the server is unreachable.

Example

Demonstrates QueryIterator() usage.

go

import (
    "context"
    "fmt"
    "io"

    "github.com/milvus-io/milvus/client/v3/milvusclient"
)

ctx := context.Background()

iter, err := client.QueryIterator(ctx,
    milvusclient.NewQueryIteratorOption("my_collection").
        WithBatchSize(500).
        WithFilter("age > 18").
        WithOutputFields("name", "age"),
)
if err != nil {
    log.Fatal(err)
}

for {
    rs, err := iter.Next(ctx)
    if err == io.EOF {
        break
    }
    if err != nil {
        log.Fatal(err)
    }
    fmt.Printf("Got %d results\n", rs.Len())
}