Query()

This method conducts metadata filtering within a collection.

func (c *GrpcClient) Query(ctx context.Context, collectionName string, partitionNames []string, expr string, outputFields []string, opts ...SearchQueryOptionFunc) (ResultSet, error)

Parameter	Description	Type
ctx	Context for the current call to work.	context.Context
collectionName	Name of a collection.	string
partitionNames	List of partition names. If left empty, all partitions are involved in this operation. Otherwise, only the specified partitions are involved.	[]string
expr	Boolean expression for metadata filtering. For details, refer to Scalar Filtering Rules.	string
outputFields	List of field names to include in the return.	[]string
opts	Extra query options. You can add multiple client.SearchQueryOptionFunc instances.	...client.SearchQueryOptionFunc

Return

A client.ResultSet, which is a slice of entity.Column.

client.ResultSet

The client.ResultSet provides the following methods for you to manipulate the query results.

Method	Return Type	Description
GetColumn(fieldName string)	entity.Column	Return the column with the provided name.
Len()	int	Return the number of entities in the query result.
Slice(start, end int)	client.ResultSet	Return a slice of the query result.

Errors

Any error in the execution of the request. Possible errors are as follows:

• ErrClientNotReady: The client is not connected to Milvus.

• ErrCollectionNotExists: The collection with the specified name does not exist.

• The call to this API fails.

Example

// query
queryRes, errQuery := mc.Query(context.Background(), collectionName, []string{}, "10< id < 20", []string{}, client.WithSearchQueryConsistencyLevel(entity.ClStrong))
if errQuery != nil {
   log.Fatal("failed to query collection:", errQuery.Error())
}
for _, res := range queryRes {
   log.Println(res.Name(), res.FieldData())
}