Skip to main content

ftBlob

ftBlob = 15

Example​

function IsBinaryLargeObject(Field: TField): Boolean;
begin
  Result := Field.DataType = ftBlob;
end;

Usage​

ftBlob identifies a generic binary large object whose bytes are normally accessed through a dataset-provided blob stream rather than the record buffer.

Additional Technical Info​

ftBlob is declaration ordinal 15 of TFieldType. It is the provider-neutral marker for a binary large object (BLOB). The value describes field metadata; it does not identify a file format, character encoding, compression method or MIME type.

Delphi normally represents this member with TBlobField. Its data is not stored in the ordinary record buffer: the installed RTL reports a field DataSize of zero and asks the dataset to create a blob stream for reads and writes. Use the field or dataset's blob-stream operations for large values. Reading AsBytes, AsVariant or AsString materialises the complete value and therefore has memory proportional to the blob size.

Treat the bytes as opaque until the schema or producer supplies a format. AsString is especially unsafe for arbitrary binary content because the generic blob path decodes bytes through the host ANSI encoding. Empty and Null are distinct provider concepts, although modified zero-length blobs require dataset-specific handling. Stream lifetime, edit state, transaction scope, maximum LOB size and concurrent access are all controlled by the concrete dataset/provider.

The example only inspects metadata and was source-reviewed; no blob, stream, dataset, database, file, runtime or image test ran.

External references

Created 2026-07-15