Creating a collection

This topic describes how to create a collection in Milvus.

A collection consists of one or more partitions. When creating a new collection, Milvus automatically creates a default partition named _default.

The following example creates a collection called book with two shards. It includes a primary key field named book_id, an INT64 scalar field named word_count, and a two-dimensional floating point vector field named book_intro. Actual applications may use vector dimensions higher than those in the example.

Definition of Collection Schema

The collection to be created must include a primary key field and a vector field. The primary key field supports INT64 and VarChar data types.

Tip: The schema definition of the collection is similar to defining a table structure in MYSQL.

First, prepare the necessary parameters, including field schemas, collection schemas, and collection names.

Before defining the collection schema, create a schema for each field in the collection. To simplify the complexity of data insertion, Milvus allows specifying a default value for each scalar field (except for the primary key field). This means that if a field is left empty during data insertion, the default value configured for this field during the field schema creation will be used.

var (
    collectionName = "book"
    )
schema := &entity.Schema{
  CollectionName: collectionName,
  Description:    "Test book search",
  Fields: []*entity.Field{
    {
      Name:       "book_id",
      DataType:   entity.FieldTypeInt64,
      PrimaryKey: true,
      AutoID:     false,
    },
    {
      Name:       "word_count",
      DataType:   entity.FieldTypeInt64,
      PrimaryKey: false,
      AutoID:     false,
    },
    {
      Name:     "book_intro",
      DataType: entity.FieldTypeFloatVector,
      TypeParams: map[string]string{
          "dim": "2",
      },
    },
  },
  EnableDynamicField: true
}
Type Parameter Description Options
entity.Schema CollectionName Name of the collection to be created N/A
Description Description of the collection to be created N/A
AutoID Switch used to enable or disable automatic ID (primary key) allocation True or False
Fields Schemas of the fields in the collection to be created. For more information, see schema N/A
EnableDynamicField Whether to enable dynamic schema. For more information on dynamic schema, see the Dynamic Schema and Collection Management User Guide N/A
entity.Field Name Name of the field to be created N/A
PrimaryKey Whether this field is a primary key. Required for primary key fields N/A
AutoID Whether the field value is auto-incremented. Required for primary key fields N/A
Description Description of the field N/A
DataType Data type of the field to be created For primary key fields: - entity.FieldTypeInt64(numpy.int64) - entity.FieldTypeVarChar(VARCHAR) For scalar fields: - entity.FieldTypeBool(Boolean) - entity.FieldTypeInt8(numpy.int8) - entity.FieldTypeInt16(numpy.int16) - entity.FieldTypeInt32(numpy.int32) - entity.FieldTypeInt64(numpy.int64) - entity.FieldTypeFloat(numpy.float32) - entity.FieldTypeDouble(numpy.double) - entity.FieldTypeVarChar(VARCHAR) For vector fields: - entity.FieldTypeBinaryVector (Binary vector) - entity.FieldTypeFloatVector (Float vector)
TypeParams Mapping to the string that sets parameters for specific data types N/A
IndexParams Mapping to the string that sets collection index parameters N/A
IsDynamic Whether this field enables dynamic schema N/A
IsPartitionKey Whether this field acts as a partition key N/A

Create a collection based on the defined structure

Next, create a collection using the specified schema.

err = milvusClient.CreateCollection(
    context.Background(), // ctx
    schema,
    2, // shardNum
)
if err != nil {
    log.Fatal("Failed to create collection: ", err.Error())
}
Parameter Description Options
ctx Context to control the API call process N/A
shardNum Number of shards in the collection to be created [1,16]

Collection Restrictions

Resource Configuration

Feature Maximum Limit
Length of collection name 255 characters
Number of partitions in collection 4,096
Number of fields in collection 64
Number of shards in collection 16

Parameter default_value

  • default_value applies only to non-array and non-JSON scalar fields.
  • default_value does not apply to primary keys.
  • The data type of default_value must be the same as the data type specified in dtype, otherwise errors may occur.
  • If auto_id is used, it is not allowed to set all remaining fields to use default values. In other words, when performing insert or update operations, you need to specify a value for at least one field, otherwise errors may occur.

Check if a collection exists

collExists, err := milvusClient.HasCollection(ctx, collectionName)
if err != nil {
    log.Fatal("Failed to check if the collection exists: ", err.Error())
}

Drop a collection

_ = milvusClient.DropCollection(ctx, collectionName)

Query all collections

collections, err := milvusClient.ListCollections(ctx)