SYSTEM CATALOG · 系统目录

pg_attribute

The catalog pg_attribute stores information about table columns. There will be exactly one pg_attribute row for every column in every table in the database. (There will also be attribute entries for indexes, and indeed all objects that have pg_class entries.) The term attribute is equivalent to column and is used for historical reasons.

首次收录 PG 9.0最近收录 PG 19当前字段 25

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_attribute

字段 / COLUMN	类型 / TYPE	说明 / DESCRIPTION
`attrelid`	`oid`NOT NULL	The table this column belongs to引用：`pg_class.oid`
`attname`	`name`NOT NULL	The column name
`atttypid`	`oid`NOT NULL	The data type of this column (zero for a dropped column)引用：`pg_type.oid`
`attlen`	`smallint`NOT NULL文档原写法：`int2`	A copy of pg_type.typlen of this column's type
`attnum`	`smallint`NOT NULL文档原写法：`int2`	The number of the column. Ordinary columns are numbered from 1 up. System columns, such as ctid, have (arbitrary) negative numbers.
`atttypmod`	`integer`NOT NULL文档原写法：`int4`	atttypmod records type-specific data supplied at table creation time (for example, the maximum length of a varchar column). It is passed to type-specific input functions and length coercion functions. The value will generally be -1 for types that do not need atttypmod.
`attndims`	`smallint`NOT NULL文档原写法：`int2`	Number of dimensions, if the column is an array type; otherwise 0. (Presently, the number of dimensions of an array is not enforced, so any nonzero value effectively means “it's an array”.)
`attbyval`	`boolean`NOT NULL文档原写法：`bool`	A copy of pg_type.typbyval of this column's type
`attalign`	`"char"`NOT NULL文档原写法：`char`	A copy of pg_type.typalign of this column's type
`attstorage`	`"char"`NOT NULL文档原写法：`char`	Normally a copy of pg_type.typstorage of this column's type. For TOAST-able data types, this can be altered after column creation to control storage policy.
`attcompression`	`"char"`NOT NULL文档原写法：`char`	The current compression method of the column. Typically this is '\0' to specify use of the current default setting (see default_toast_compression). Otherwise, 'p' selects pglz compression, while 'l' selects LZ4 compression. However, this field is ignored whenever attstorage does not allow compression.
`attnotnull`	`boolean`NOT NULL文档原写法：`bool`	This column has a (possibly invalid) not-null constraint.
`atthasdef`	`boolean`NOT NULL文档原写法：`bool`	This column has a default expression or generation expression, in which case there will be a corresponding entry in the pg_attrdef catalog that actually defines the expression. (Check attgenerated to determine whether this is a default or a generation expression.)
`atthasmissing`	`boolean`NOT NULL文档原写法：`bool`	This column has a value which is used where the column is entirely missing from the row, as happens when a column is added with a non-volatile DEFAULT value after the row is created. The actual value used is stored in the attmissingval column.
`attidentity`	`"char"`NOT NULL文档原写法：`char`	If a zero byte (''), then not an identity column. Otherwise, a = generated always, d = generated by default.
`attgenerated`	`"char"`NOT NULL文档原写法：`char`	If a zero byte (''), then not a generated column. Otherwise, s = stored, v = virtual. A stored generated column is physically stored like a normal column. A virtual generated column is physically stored as a null value, with the actual value being computed at run time.
`attisdropped`	`boolean`NOT NULL文档原写法：`bool`	This column has been dropped and is no longer valid. A dropped column is still physically present in the table, but is ignored by the parser and so cannot be accessed via SQL.
`attislocal`	`boolean`NOT NULL文档原写法：`bool`	This column is defined locally in the relation. Note that a column can be locally defined and inherited simultaneously.
`attinhcount`	`smallint`NOT NULL文档原写法：`int2`	The number of direct ancestors this column has. A column with a nonzero number of ancestors cannot be dropped nor renamed.
`attcollation`	`oid`NOT NULL	The defined collation of the column, or zero if the column is not of a collatable data type引用：`pg_collation.oid`
`attstattarget`	`smallint`文档原写法：`int2`	attstattarget controls the level of detail of statistics accumulated for this column by ANALYZE. A zero value indicates that no statistics should be collected. A null value says to use the system default statistics target. The exact meaning of positive values is data type-dependent. For scalar data types, attstattarget is both the target number of “most common values” to collect, and the target number of histogram bins to create.
`attacl`	`aclitem[]`	Column-level access privileges, if any have been granted specifically on this column
`attoptions`	`text[]`	Attribute-level options, as “keyword=value” strings
`attfdwoptions`	`text[]`	Attribute-level foreign data wrapper options, as “keyword=value” strings
`attmissingval`	`anyarray`	This column has a one element array containing the value used when the column is entirely missing from the row, as happens when the column is added with a non-volatile DEFAULT value after the row is created. The value is only used when atthasmissing is true. If there is no value the column is null.

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	18	19
`attrelid`
`attname`
`atttypid`
`attstattarget`
`attlen`
`attnum`
`attndims`
`attcacheoff`												−	–
`atttypmod`
`attbyval`
`attstorage`
`attalign`
`attnotnull`
`atthasdef`
`attisdropped`
`attislocal`
`attinhcount`
`attacl`
`attoptions`
`attcollation`	–
`attfdwoptions`	–	–
`attidentity`	–	–	–	–	–	–	–
`atthasmissing`	–	–	–	–	–	–	–	–
`attmissingval`	–	–	–	–	–	–	–	–
`attgenerated`	–	–	–	–	–	–	–	–	–
`attcompression`	–	–	–	–	–	–	–	–	–	–	–

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 18 ← 17

− attcacheoff2 处字段说明更新

PostgreSQL 17 ← 16

~ attstattarget: not_null: true → false↕ 字段顺序变化1 处字段说明更新

PostgreSQL 16 ← 15

~ attinhcount: integer → smallint~ attndims: integer → smallint~ attstattarget: integer → smallint↕ 字段顺序变化

PostgreSQL 14 ← 13

+ attcompression↕ 字段顺序变化2 处字段说明更新

PostgreSQL 12 ← 11

+ attgenerated2 处字段说明更新

PostgreSQL 11 ← 10

+ atthasmissing+ attmissingval

PostgreSQL 10 ← 9.6

+ attidentity4 处字段说明更新

PostgreSQL 9.5 ← 9.4

1 处字段说明更新

PostgreSQL 9.2 ← 9.1

+ attfdwoptions

PostgreSQL 9.1 ← 9.0

+ attcollation

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。