queryIterator()

This method returns a query iterator to iterate data.

public QueryIterator queryIterator(QueryIteratorReq request)

Request Syntax

queryIterator(QueryIteratorReq.builder()
        .collectionName(String collectionName)
        .outputFields(List<String> outputFields)
        .expr(String expr)
        .batchSize(long size)
        .consistencyLevel(ConsistencyLevel consistencyLevel)
        .offset(long offset)
        .limit(long limit)
        .build());

BUILDER METHODS:

• collectionName(String collectionName)

  The name of an existing collection.

• outputFields(List<String> outputFields)

  A list of field names to include in each entity in return.

  The value defaults to None. If left unspecified, all fields in the collection are selected as the output fields.

• expr(String expr)

  A scalar filtering condition to filter matching entities.

  You can set this parameter to an empty string to skip scalar filtering. To build a scalar filtering condition, refer to Boolean Expression Rules.

• batchSize(long size)

A value to define the number of entities returned per batch.

• consistencyLevel(ConsistencyLevel consistencyLevel)

  The consistency level of the target collection.

  The value defaults to the one specified when you create the current collection, with options of Strong (0), Bounded (1), Session (2), and Eventually (3).

  what is the consistency level?

  Consistency in a distributed database specifically refers to the property that ensures every node or replica has the same view of data when writing or reading data at a given time.

  Milvus supports four consistency levels: Strong, Bounded Staleness, Session, and Eventually. The default consistency level in Milvus is Bounded Staleness.

  You can easily tune the consistency level when conducting a vector similarity search or query to make it best suit your application.

• offset(long offset)

  The number of records to skip in the query result.

  You can use this parameter in combination with limit to enable pagination.

  The sum of this value and limit should be less than 16,384.

• limit(long limit)

  The number of records to return in the query result.

  You can use this parameter in combination with offset to enable pagination.

  The sum of this value and offset should be less than 16,384.

RETURN TYPE:

QueryIterator

RETURNS:

A QueryIterator object to iterate data.

METHODS:

• List<QueryResultsWrapper.RowRecord> next()

Return a batch of results.

• close()

Release the cache results.

EXCEPTIONS:

• MilvusClientExceptions

  This exception will be raised when any error occurs during this operation.

Example

QueryIterator queryIterator = client.queryIterator(QueryIteratorReq.builder()
        .collectionName(COLLECTION_NAME)
        .expr("id < 300")
        .outputFields(Lists.newArrayList("id", "vector"))
        .batchSize(50L)
        .offset(5)
        .limit(400)
        .consistencyLevel(ConsistencyLevel.BOUNDED)
        .build());

while (true) {
    List<QueryResultsWrapper.RowRecord> res = queryIterator.next();
    if (res.isEmpty()) {
        System.out.println("query iteration finished, close");
        queryIterator.close();
        break;
    }

    for (QueryResultsWrapper.RowRecord record : res) {
        System.out.println(record);
    }
}