SYSTEM CATALOG · System catalog

pg_description

PostgreSQL documentation ↗Source definition ↗

The catalog pg_description stores optional descriptions (comments) for each database object. Descriptions can be manipulated with the COMMENT command and viewed with psql's \d commands. Descriptions of many built-in system objects are provided in the initial contents of pg_description. See also pg_shdescription, which performs a similar function for descriptions involving objects that are shared across a database cluster.

First seen PG 9.0Last seen PG 19Columns 4

9.0 9.1 9.2 9.3 9.4 9.5 9.6 10 11 12 13 14 15 16 17 18 19^β3

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

Columns PostgreSQL 18

pg_description

COLUMN	TYPE	DESCRIPTION
`objoid`	`oid`NOT NULL	The OID of the object this description pertains toReferences:`any OID column`
`classoid`	`oid`NOT NULL	The OID of the system catalog this object appears inReferences:`pg_class.oid`
`objsubid`	`integer`NOT NULLDocumented as:`int4`	For a comment on a table column, this is the column number (the objoid and classoid refer to the table itself). For all other object types, this column is zero.
`description`	`text`NOT NULL	Arbitrary text that serves as the description of this object

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.

Columns	Type	attnum
`tableoid`	`oid`	-6
`cmax`	`cid`	-5
`xmax`	`xid`	-4
`cmin`	`cid`	-3
`xmin`	`xid`	-2
`ctid`	`tid`	-1

Column evolution matrix

Hover a cell for the column type

PresentAdded / type or attribute changeRemoved

COLUMN	9.0	9.1	9.2	9.3	9.4	9.5	9.6	10	11	12	13	14	15	16	17	18	19
`objoid`
`classoid`
`objsubid`
`description`

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 9.5 ← 9.4

~ description: not_null: false → true

Compare any two versions

FROMTOInclude description updates

Pick two versions to see added, removed, and retyped columns. The interactive comparison needs JavaScript; the evolution timeline reads fine without it.