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SYSTEM CATALOG · System catalog

pg_largeobject

PostgreSQL documentation ↗Source definition ↗

The catalog pg_largeobject 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 2 kB). Prior to PostgreSQL 9.0, there was no permission structure associated with large objects. As a result, pg_largeobject was publicly readable and could be used to obtain the OIDs (and contents) of all large objects in the system. This is no longer the case; use pg_largeobject_metadata to obtain a list of large object OIDs.

First seen PG 9.0Last seen PG 19Columns 3
9.09.19.29.39.49.59.610111213141516171819β3

Checked column by column against a PostgreSQL 18.6 instance · Raw measurement record ↗

Columns PostgreSQL 18

pg_largeobject
COLUMNTYPEDESCRIPTION
loid oidNOT NULL Identifier of the large object that includes this pageReferences:pg_largeobject_metadata.oid
pageno integerNOT NULLDocumented as:int4 Page number of this page within its large object (counting from zero)
data byteaNOT NULL Actual data stored in the large object. This will never be more than LOBLKSIZE bytes and might be less.

Columns marked "implicit" are not included in SELECT *; some early statistics views are completed from same-version source, and the extra provenance is shown in the column description.

Common system columns 6

System attributes PostgreSQL provides, normally not expanded by SELECT *. Kept separately so they are not mixed in with ordinary columns.

ColumnsTypeattnum
tableoidoid-6
cmaxcid-5
xmaxxid-4
cmincid-3
xminxid-2
ctidtid-1

Column evolution matrix

Hover a cell for the column type
PresentAdded / type or attribute changeRemoved
COLUMN9.09.19.29.39.49.59.610111213141516171819
loid
pageno
data

9.0 is the coverage baseline; a column already present in the baseline is not marked as added. The matrix aligns columns by name, so a rename appears as the old column removed and a new column added.

Evolution timeline

Changes between adjacent majors

PostgreSQL 10 ← 9.6

Catalog description updated

PostgreSQL 9.5 ← 9.4

~ data: not_null: false → true

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