SYSTEM CATALOG · 系统目录

pg_description

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.

首次收录 PG 9.0最近收录 PG 19当前字段 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

已与 PostgreSQL 18.6 实例逐字段核对 · 原始实测记录 ↗

字段结构 PostgreSQL 18

pg_description

字段 / COLUMN	类型 / TYPE	说明 / DESCRIPTION
`objoid`	`oid`NOT NULL	The OID of the object this description pertains to引用：`any OID column`
`classoid`	`oid`NOT NULL	The OID of the system catalog this object appears in引用：`pg_class.oid`
`objsubid`	`integer`NOT NULL文档原写法：`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

标记“隐式列”的字段不包含在 SELECT * 中；部分早期统计视图由同版本源码补全，额外来源会显示在字段说明中。

通用系统列 6

PostgreSQL 提供的系统属性，通常不在 SELECT * 中展开。单独保留，不与普通字段混算。

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

字段演化矩阵

悬停查看字段类型

存在新增 / 类型或属性变化移除

字段 / 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 是收录基线；基线中已存在的字段不标记为新增。矩阵按字段名称对齐，重命名显示为旧字段移除与新字段新增。

演化时间线

相邻大版本的变化

PostgreSQL 9.5 ← 9.4

~ description: not_null: false → true

比较任意两个版本

起始版本 / FROM目标版本 / TO包含描述更新

选择两个版本，查看字段的新增、移除与类型变化。交互比较需要 JavaScript；演化时间线可直接阅读。