Collection schema get from go-sdk can`t get the dynamic field

[Mutezebra]

i want to get all of fields of collection, include dynamic field, but i can`t

col, err := mclient.DescribeCollection(ctx, "book_store") // Return the name and schema of the collection.
	if err != nil {
		return
	}

for _, filed := range col.Schema.Fields {
	log.Printf("%#v\n", filed)
}

output:

2024/05/10 01:43:04 &entity.Field{ID:100, Name:"book_id", PrimaryKey:true, AutoID:true, Description:"", DataType:5, TypeParams:map[string]string{}, IndexParams:map[string]string{}, IsDynamic:false, IsPartitionKey:false}
2024/05/10 01:43:04 &entity.Field{ID:101, Name:"book_count", PrimaryKey:false, AutoID:false, Description:"", DataType:5, TypeParams:map[string]string{}, IndexParams:map[string]string{}, IsDynamic:false, IsPartitionKey:false}
2024/05/10 01:43:04 &entity.Field{ID:102, Name:"book_intro", PrimaryKey:false, AutoID:false, Description:"", DataType:101, TypeParams:map[string]string{"dim":"2"}, IndexParams:map[string]string{}, IsDynamic:false, IsPartitionKey:false}

And i am sure all of entity in collection have the dynamic field of book_hot
The picture if from attu

I found that some Milvus sources attempt to use schemapb.FieldSchema. The GetIsDynamic method is utilized to ascertain whether a field is dynamic. Therefore, I am curious to know if there exists a method in the SDK to retrieve all fields, including the dynamic ones.

In milvus source like

for _, field := range schema.GetFields() {
		// do something
		if field.GetIsDynamic() {
			continue
		}
               // do something
}

[yhmo]

It is by design. All the SDKs follow this behavior.
The dynamic field is not a standard field, controlled by the enable_dynamic_field of CollectionSchema, not listed in fields. Each collection has at most one dynamic field. The datatype of a dynamic field is JSON.

You can use the flag enable_dynamic_field of CollectionSchema to check whether there is a dynamic field inside the collection.

For example, in python sdk:

fields=[
    FieldSchema(name="id", dtype=DataType.INT64, is_primary=True, auto_id=True),
    FieldSchema(name="vector", dtype = DataType.FLOAT_VECTOR, dim=dim),
]

schema = CollectionSchema(fields=fields, enable_dynamic_field=True)

collection = Collection(name=collection_name, schema=schema)
print(f"Collection '{collection_name}' created")

collection = Collection(collection_name)
print(collection.schema)

The schema is printed like this:

{
	'auto_id': True,
	'description': '',
	'fields': [{
		'name': 'id',
		'description': '',
		'type': < DataType.INT64: 5 > ,
		'is_primary': True,
		'auto_id': True
	}, {
		'name': 'vector',
		'description': '',
		'type': < DataType.FLOAT_VECTOR: 101 > ,
		'params': {
			'dim': 512
		}
	}],
	'enable_dynamic_field': True
}

[Mutezebra]

Thanks for your answer. Maybe is my describe not enable clearly, what i want to konw is the exist format of dynamic. I got the dynamic field info by building source code.

&schemapb.FieldSchema{FieldID:103, Name:"$meta", IsPrimaryKey:false, Description:"dynamic schema", DataType:23, TypeParams:[]*commonpb.KeyValuePair(nil), IndexParams:[]*commonpb.KeyValuePair(nil), AutoID:false, State:0, ElementType:0, DefaultValue:(*schemapb.ValueField)(nil), IsDynamic:true, IsPartitionKey:false, IsClusteringKey:false, XXX_NoUnkeyedLiteral:struct {}{}, XXX_unrecognized:[]uint8(nil), XXX_sizecache:0}

And by reading some of the source code, I have a clearer understanding of the dynamic field，my problem is solved. Thanks !