BLOBS

Working with BLOBs (Binary Large Objects)

Use cases

• Read BLOB
• Create BLOB

Technical design

Definitions

• BLOB.OwnerRecord: QName of the record that owns the BLOB
• BLOB.OwnerRecordField: Name of the field that owns the BLOB
• CUD collection: Collection of CUDs (Create, Update, Deactivate) that are executed in the same transaction

Components overview

• ~wdoc.sys.Workspace.BLOB~covrd¹✅: WDoc for storing BLOB metadata
  • This is the only WRecord that can be referenced from CDocs
  • CDocs reference BLOBs by fields of the blob type
  • blob type is implemented as a ref to WDoc record
• ~tuc.HandleBLOBReferences~covrd²✅: Handling fields of the blob type by command processor

CP: tuc.HandleBLOBReferences

• Validate that every modified record its blob fields satisifies the following conditions:
  • ~err.BLOBOwnerRecordIDMustBeEmpty~covrd³✅: Target BLOB.OwnerRecordID must be empty
  • ~err.BLOBOwnerRecordMismatch~covrd⁴✅: BLOB.OwnerRecord does not match the record QName
  • ~err.BLOBOwnerRecordFieldMismatch~covrd⁵✅: BLOB.OwnerRecordField does not match the record field name
  • ~err.DuplicateBLOBReference~covrd⁶✅: Multiple records in CUD collection cannot refer to the same BLOB
• ~cmp.UpdateBLOBOwnership~covrd⁷✅: Operator of the CP that updates the BLOB.OwnerRecordID and BLOB.OwnerRecordField fields in the BLOB table

Footnotes

1. [~server.blobs/wdoc.sys.Workspace.BLOB~impl] pkg/sys/sys.vsql:63:impl ↩

2. [~server.blobs/tuc.HandleBLOBReferences~impl] pkg/processors/command/impl.go:538:impl, pkg/sys/blobber/provide.go:27:impl ↩

3. [~server.blobs/err.BLOBOwnerRecordIDMustBeEmpty~impl] pkg/sys/blobber/provide.go:55:impl ↩

4. [~server.blobs/err.BLOBOwnerRecordMismatch~impl] pkg/sys/blobber/provide.go:68:impl ↩

5. [~server.blobs/err.BLOBOwnerRecordFieldMismatch~impl] pkg/sys/blobber/provide.go:69:impl ↩

6. [~server.blobs/err.DuplicateBLOBReference~impl] pkg/sys/blobber/provide.go:61:impl ↩

7. [~server.blobs/cmp.UpdateBLOBOwnership~impl] pkg/processors/command/impl.go:537:impl ↩