query()

This operation conducts a scalar filtering with a specified boolean expression.

Request Syntax

query(
    expr: str, 
    output_fields: list[str] | None, 
    partition_names: list[str] | None, 
    timeout: float | None
    **kwargs
)

PARAMETERS:

• expr (str) -

  [REQUIRED]

  A scalar filtering condition to filter matching entities.

  You can set this parameter to an empty string to skip scalar filtering. In this case, you should also set limit to restrict the number of entities in return.

  To build a scalar filtering condition, refer to Boolean Expression Rules.

• output_fields (list) -

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

  The value defaults to None. If left unspecified, only the primary field is included.

• partition_names (list)

  A list of partition names.

  The value defaults to None. If specified, only the specified partitions are involved in queries.

• timeout (float)

  The timeout duration for this operation. Setting this to None indicates that this operation timeouts when any response arrives or any error occurs.

• kwargs:

  • consistency_level (str | int) -

    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.

  • guarantee_timestamp (int) -

    A valid timestamp.

    If this parameter is set, MilvusZilliz Cloud executes the query only if all entities inserted before this timestamp are visible to query nodes.

    notes

    This parameter is valid when the default consistency level applies.

  • graceful_time (int) -

    A period of time in seconds.

    The value defaults to 5. If this parameter is set, MilvusZilliz Cloud calculates the guarantee timestamp by subtracting this from the current timestamp.

    notes

    This parameter is valid when a consistency level other than the default one applies.

  • offset (int) -

    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 (int) -

    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:

list[dict]

RETURNS:

A list of dictionaries with each dictionary representing a queried entity.

EXCEPTIONS:

• MilvusException

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

• DataTypeNotMatchException

  This exception will be raised when a parameter value doesn’t match the required data type.

Examples

from pymilvus import Collection, CollectionSchema, FieldSchema, DataType

schema = CollectionSchema([
    FieldSchema("id", DataType.INT64, is_primary=True),
    FieldSchema("vector", DataType.FLOAT_VECTOR, dim=5)
])

# Create a collection
collection = Collection(
    name="test_collection",
    schema=schema
)

# Insert a list of columns
res = collection.insert(
    data=[
        [0,1,2,3,4,5,6,7,8,9],               # id
        [                                    # vector
            [0.1,0.2,-0.3,-0.4,0.5],
            [0.3,-0.1,-0.2,-0.6,0.7],
            [-0.6,-0.3,0.2,0.8,0.7],
            [0.6,0.2,-0.3,-0.8,0.5],
            [0.3,0.1,-0.2,-0.6,-0.7],
            [0.1,0.2,-0.3,-0.4,0.5],
            [0.3,-0.1,-0.2,-0.6,0.7],
            [-0.6,-0.3,0.2,0.8,0.7],
            [0.6,0.2,-0.3,-0.8,0.5],
            [0.3,0.1,-0.2,-0.6,-0.7],
        ],
    ]
)

# Query without any scalar filtering condition
# This query returns entities with their ids from 0 to 4.
res = collection.query(
    expr="",
    limit=5,
) 

# Query with pagination
# This query returns entities with their ids from 5 to 9.
res = collection.query(
    expr="",
    offset=5
    limit=5
)

# Query with a scalar filtering condition
res = collection.query(
    expr="id in [6,7,8]",
)

# Query within a partition
res = collection.query(
    expr="id in [6,7,8]",
    partition_names=["partitionA"],
)

# Query with specified output fields
res = collection.query(
    expr="id in [6,7,8]",
    output_fields=["id", "vector"],
)

# Query with a customized consistency level
res = collection.query(
    expr="",
    consistency_level=3,
    graceful_time=6
)

Related operations

The following operations are related to query():

• delete()

• insert()

• search()

• search_iterator()

• query_iterator()

• upsert()