External Collection Limits

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Because Zilliz Cloud does not store raw data for external collections and only maintains metadata and mappings to the external data source, external collections are read-only. As a result, you cannot perform write or maintenance operations from the Zilliz Cloud side, including insert, upsert, delete, import, flush, and compact.

Compared with managed collections, external collections have the following limitations:

• You need to use an API key to access external collections.

• Zilliz Cloud does not enforce primary key uniqueness, and you cannot configure a primary key or AutoID.

• You cannot enable the dynamic field.

• You cannot use partitions. As a result, partition key and are not supported.

• You cannot define functions in the schema.

• You cannot modify the schema of an external collection after it is created.

• You cannot use text match with BM25.

• To make external data queryable, you must first create an index and then manually trigger RefreshExternalCollection so that Zilliz Cloud can build metadata and indexes for the data.

• Backup, restore, and migration are currently not supported for external collections.

The following table compares the operations supported by external collections and managed collections in detail.

		Managed Collection (Serving Cluster)	External Collection (Serving Cluster or Databases for On-Demand Compute)	Managed Collection (On-Demand Compute Database)
Collection Management	CreateCollection	✅	✅	✅
	DropCollection	✅	✅	✅
	DescribeCollection	✅	✅	✅
	RenameCollection	✅	✅	✅
	Dynamic Field	✅	❌	✅
	Primary Key	✅	❌	✅
	Auto ID	✅	❌	✅
	TTL	✅	❌	❌
	Nullable/Default Value	✅	❌	✅
	Loaded Entities	✅	✅	✅
	Allow Insert Auto ID	✅	❌	✅
	MMAP	✅	❌	✅
	Timezone	✅	✅	✅
Schema	AddField	✅	❌	✅
	AlterField	✅	❌	✅
Partition	CreatePartition	✅	❌	✅
	DropPartition	✅	❌	✅
	Partition Key	✅	❌	✅
Data writes	Insert	✅	❌	❌
	Delete	✅	❌	❌
	Upsert	✅	❌	❌
	BulkInsert / Import	✅	❌	✅
	Flush	✅	❌	❌
	Shard	✅	❌	✅
	Truncate	✅	❌	✅
Data sync	RefreshExternalCollection	—	✅	—
	GetRefreshProgress	—	✅	—
	ListRefreshJobs	—	✅	—
Index	CreateIndex	✅	✅	✅
	DropIndex	✅	❌	❌
	DescribeIndex	✅	✅	✅
Load/Release	LoadCollection	✅	✅	✅
	ReleaseCollection	✅	✅	✅
Search/Query	Search	✅	✅	✅
	Query	✅	✅	✅
	HybridSearch	✅	✅	✅
	Functions	✅	❌	✅
	Full-text Search/Text Match	✅	❌	✅
Maintenance	Manual Compaction	✅	❌	✅
	Clustering Key	✅	❌	✅
	Backup & restore	✅	❌	❌
	Migration	✅	❌	❌