SYSTEM CATALOG · 系统目录

pg_class

The catalog pg_class describes tables and other objects that have columns or are otherwise similar to a table. This includes indexes (but see also pg_index), sequences (but see also pg_sequence), views, materialized views, composite types, and TOAST tables; see relkind. Below, when we mean all of these kinds of objects we speak of “relations”. Not all of pg_class's columns are meaningful for all relation kinds.

首次收录 PG 9.0最近收录 PG 19当前字段 34

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_class

字段 / COLUMN	类型 / TYPE	说明 / DESCRIPTION
`oid`	`oid`NOT NULL	Row identifier
`relname`	`name`NOT NULL	Name of the table, index, view, etc.
`relnamespace`	`oid`NOT NULL	The OID of the namespace that contains this relation引用：`pg_namespace.oid`
`reltype`	`oid`NOT NULL	The OID of the data type that corresponds to this table's row type, if any; zero for indexes, sequences, and toast tables, which have no pg_type entry引用：`pg_type.oid`
`reloftype`	`oid`NOT NULL	For typed tables, the OID of the underlying composite type; zero for all other relations引用：`pg_type.oid`
`relowner`	`oid`NOT NULL	Owner of the relation引用：`pg_authid.oid`
`relam`	`oid`NOT NULL	The access method used to access this table or index. Not meaningful if the relation is a sequence or has no on-disk file, except for partitioned tables, where, if set, it takes precedence over default_table_access_method when determining the access method to use for partitions created when one is not specified in the creation command.引用：`pg_am.oid`
`relfilenode`	`oid`NOT NULL	Name of the on-disk file of this relation; zero means this is a “mapped” relation whose disk file name is determined by low-level state
`reltablespace`	`oid`NOT NULL	The tablespace in which this relation is stored. If zero, the database's default tablespace is implied. Not meaningful if the relation has no on-disk file, except for partitioned tables, where this is the tablespace in which partitions will be created when one is not specified in the creation command.引用：`pg_tablespace.oid`
`relpages`	`integer`NOT NULL文档原写法：`int4`	Size of the on-disk representation of this table in pages (of size BLCKSZ). This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
`reltuples`	`real`NOT NULL文档原写法：`float4`	Number of live rows in the table. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX. If the table has never yet been vacuumed or analyzed, reltuples contains -1 indicating that the row count is unknown.
`relallvisible`	`integer`NOT NULL文档原写法：`int4`	Number of pages that are marked all-visible in the table's visibility map. This is only an estimate used by the planner. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
`relallfrozen`	`integer`NOT NULL文档原写法：`int4`	Number of pages that are marked all-frozen in the table's visibility map. This is only an estimate used for triggering autovacuums. It can also be used along with relallvisible for scheduling manual vacuums and tuning vacuum's freezing behavior. It is updated by VACUUM, ANALYZE, and a few DDL commands such as CREATE INDEX.
`reltoastrelid`	`oid`NOT NULL	OID of the TOAST table associated with this table, zero if none. The TOAST table stores large attributes “out of line” in a secondary table.引用：`pg_class.oid`
`relhasindex`	`boolean`NOT NULL文档原写法：`bool`	True if this is a table and it has (or recently had) any indexes
`relisshared`	`boolean`NOT NULL文档原写法：`bool`	True if this table is shared across all databases in the cluster. Only certain system catalogs (such as pg_database) are shared.
`relpersistence`	`"char"`NOT NULL文档原写法：`char`	p = permanent table/sequence, u = unlogged table/sequence, t = temporary table/sequence
`relkind`	`"char"`NOT NULL文档原写法：`char`	r = ordinary table, i = index, S = sequence, t = TOAST table, v = view, m = materialized view, c = composite type, f = foreign table, p = partitioned table, I = partitioned index
`relnatts`	`smallint`NOT NULL文档原写法：`int2`	Number of user columns in the relation (system columns not counted). There must be this many corresponding entries in pg_attribute. See also pg_attribute.attnum.
`relchecks`	`smallint`NOT NULL文档原写法：`int2`	Number of CHECK constraints on the table; see pg_constraint catalog
`relhasrules`	`boolean`NOT NULL文档原写法：`bool`	True if table has (or once had) rules; see pg_rewrite catalog
`relhastriggers`	`boolean`NOT NULL文档原写法：`bool`	True if table has (or once had) triggers; see pg_trigger catalog
`relhassubclass`	`boolean`NOT NULL文档原写法：`bool`	True if table or index has (or once had) any inheritance children or partitions
`relrowsecurity`	`boolean`NOT NULL文档原写法：`bool`	True if table has row-level security enabled; see pg_policy catalog
`relforcerowsecurity`	`boolean`NOT NULL文档原写法：`bool`	True if row-level security (when enabled) will also apply to table owner; see pg_policy catalog
`relispopulated`	`boolean`NOT NULL文档原写法：`bool`	True if relation is populated (this is true for all relations other than some materialized views)
`relreplident`	`"char"`NOT NULL文档原写法：`char`	Columns used to form “replica identity” for rows: d = default (primary key, if any), n = nothing, f = all columns, i = index with indisreplident set (same as nothing if the index used has been dropped)
`relispartition`	`boolean`NOT NULL文档原写法：`bool`	True if table or index is a partition
`relrewrite`	`oid`NOT NULL	For new relations being written during a DDL operation that requires a table rewrite, this contains the OID of the original relation; otherwise zero. That state is only visible internally; this field should never contain anything other than zero for a user-visible relation.引用：`pg_class.oid`
`relfrozenxid`	`xid`NOT NULL	All transaction IDs before this one have been replaced with a permanent (“frozen”) transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent transaction ID wraparound or to allow pg_xact to be shrunk. Zero (InvalidTransactionId) if the relation is not a table.
`relminmxid`	`xid`NOT NULL	All multixact IDs before this one have been replaced by a transaction ID in this table. This is used to track whether the table needs to be vacuumed in order to prevent multixact ID wraparound or to allow pg_multixact to be shrunk. Zero (InvalidMultiXactId) if the relation is not a table.
`relacl`	`aclitem[]`	Access privileges; see Section 5.8 for details
`reloptions`	`text[]`	Access-method-specific options, as “keyword=value” strings
`relpartbound`	`pg_node_tree`	If table is a partition (see relispartition), internal representation of the partition bound

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
`oid`
`relname`
`relnamespace`
`reltype`
`reloftype`
`relowner`
`relam`
`relfilenode`
`reltablespace`
`relpages`
`reltuples`
`reltoastrelid`
`reltoastidxid`					−	–	–	–	–	–	–	–	–	–	–	–	–
`relhasindex`
`relisshared`
`relistemp`		−	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`relkind`
`relnatts`
`relchecks`
`relhasoids`										−	–	–	–	–	–	–	–
`relhaspkey`									−	–	–	–	–	–	–	–	–
`relhasexclusion`		−	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`relhasrules`
`relhastriggers`
`relhassubclass`
`relfrozenxid`
`relacl`
`reloptions`
`relpersistence`	–
`relallvisible`	–	–
`relispopulated`	–	–	–
`relminmxid`	–	–	–
`relreplident`	–	–	–	–
`relrowsecurity`	–	–	–	–	–
`relforcerowsecurity`	–	–	–	–	–
`relispartition`	–	–	–	–	–	–	–
`relpartbound`	–	–	–	–	–	–	–
`relrewrite`	–	–	–	–	–	–	–	–
`relallfrozen`	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–

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 19 ← 18

3 处字段说明更新

PostgreSQL 18 ← 17

+ relallfrozen

PostgreSQL 17 ← 16

2 处字段说明更新

PostgreSQL 15 ← 14

2 处字段说明更新

PostgreSQL 14 ← 13

8 处字段说明更新

PostgreSQL 12 ← 11

− relhasoids~ oid: 隐式列 → 常规列5 处字段说明更新

PostgreSQL 11 ← 10

+ relrewrite− relhaspkey3 处字段说明更新目录说明更新

PostgreSQL 10 ← 9.6

+ relispartition+ relpartbound6 处字段说明更新目录说明更新

PostgreSQL 9.5 ← 9.4

+ relrowsecurity+ relforcerowsecurity1 处字段说明更新

PostgreSQL 9.4 ← 9.3

+ relreplident− reltoastidxid

PostgreSQL 9.3 ← 9.2

+ relispopulated+ relminmxid2 处字段说明更新目录说明更新

PostgreSQL 9.2 ← 9.1

+ relallvisible

PostgreSQL 9.1 ← 9.0

+ relpersistence− relistemp− relhasexclusion1 处字段说明更新

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。