QueryIterator()

Addedv2.6.xModifiedv2.6.2

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.

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

Request Syntax

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

OPTION METHODS:

• NewQueryIteratorOption(collectionName string) -

  [REQUIRED]

  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.

• 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).

RETURNS:

QueryIterator, error

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

EXCEPTIONS:

• error - The specified collection does not exist, invalid parameters, or the server is unreachable.

Example

import (
    "context"
    "fmt"
    "io"

    "github.com/milvus-io/milvus/client/v2/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())
}

QueryIterator

The QueryIterator interface returned by the QueryIterator() method. It has a single method:

• Next(ctx context.Context) -

  Returns the next batch of query results as a ResultSet. When all results have been consumed, returns io.EOF as the error.