Greenplum Database does not support the PostgreSQL large object facility for streaming user data that is stored in large-object structures.
pg_largeobject system catalog table holds the data making up ‘large objects’. A large object is identified by an OID assigned when it is created. Each large object is broken into segments or ‘pages’ small enough to be conveniently stored as rows in
pg_largeobject. The amount of data per page is defined to be
LOBLKSIZE (which is currently
BLCKSZ/4, or typically 8K).
Each row of
pg_largeobject holds data for one page of a large object, beginning at byte offset (pageno
* LOBLKSIZE) within the object. The implementation allows sparse storage: pages may be missing, and may be shorter than
LOBLKSIZE bytes even if they are not the last page of the object. Missing regions within a large object read as zeroes.
||oid||Identifier of the large object that includes this page.|
||int4||Page number of this page within its large object (counting from zero).|
||bytea||Actual data stored in the large object. This will never be more than
Parent topic: System Catalogs Definitions