pg_sequence 是一个 系统目录 表，它与序列在 pg_class 中的主条目结合，存储有关序列的信息。
pg_sequence 在 PostgreSQL 10 中添加。
备注
此更改将与序列关联的大部分元数据从其关联的 关系 移动到此 系统目录 表中。这意味着 ALTER SEQUENCE 更新现在完全是事务性的。
该 系统目录 视图 pg_sequences 以更易访问的形式显示序列信息，并且列名与以前在 序列关系 中存在的列名匹配。
有关更改的更多详细信息，请参阅 PostgreSQL 10 发行说明。
按PostgreSQL版本定义
pg_sequence (PostgreSQL 17)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" PRIMARY KEY, btree (seqrelid)
文档: pg_sequence
pg_sequence (PostgreSQL 16)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" PRIMARY KEY, btree (seqrelid)
文档: pg_sequence
pg_sequence (PostgreSQL 15)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" PRIMARY KEY, btree (seqrelid)
文档: pg_sequence
pg_sequence (PostgreSQL 14)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" PRIMARY KEY, btree (seqrelid)
文档: pg_sequence
pg_sequence (PostgreSQL 13)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" UNIQUE, btree (seqrelid)
文档: pg_sequence
pg_sequence (PostgreSQL 12)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" UNIQUE, btree (seqrelid)
文档: pg_sequence
pg_sequence (PostgreSQL 11)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" UNIQUE, btree (seqrelid)
文档: pg_sequence
pg_sequence (PostgreSQL 10)
Table "pg_catalog.pg_sequence"
Column | Type | Collation | Nullable | Default
--------------+---------+-----------+----------+---------
seqrelid | oid | | not null |
seqtypid | oid | | not null |
seqstart | bigint | | not null |
seqincrement | bigint | | not null |
seqmax | bigint | | not null |
seqmin | bigint | | not null |
seqcache | bigint | | not null |
seqcycle | boolean | | not null |
Indexes:
"pg_sequence_seqrelid_index" UNIQUE, btree (seqrelid)
文档: pg_sequence
更改历史记录
自 PostgreSQL 10 中添加以来，此表没有被修改过。
- PostgreSQL 10
- 添加 (提交 1753b1b0)
示例
在 PostgreSQL 9.6 及更早版本中，与序列关联的元数据存储在其关联的 关系 中，例如
postgres=# CREATE SEQUENCE foo; CREATE SEQUENCE
postgres=# SELECT * from public.foo; -[ RECORD 1 ]-+-------------------- sequence_name | foo last_value | 1 start_value | 1 increment_by | 1 max_value | 9223372036854775807 min_value | 1 cache_value | 1 log_cnt | 0 is_cycled | f is_called | f
从 PostgreSQL 10 开始，序列关系 仅包含 nextval() 函数修改的字段（last_value、log_cnt 和 is_called），例如
postgres=# CREATE SEQUENCE foo;
CREATE SEQUENCE
postgres=# SELECT * from public.foo;
last_value | log_cnt | is_called
------------+---------+-----------
1 | 0 | f
(1 row)
其余元数据存储在 pg_sequence 中，例如
postgres=# SELECT * FROM pg_sequence WHERE seqrelid='foo'::REGCLASS; -[ RECORD 1 ]+-------------------- seqrelid | 16455 seqtypid | 20 seqstart | 1 seqincrement | 1 seqmax | 9223372036854775807 seqmin | 1 seqcache | 1 seqcycle | f
参考文献
- PostgreSQL 文档： pg_sequence
有用链接
- 一次性检查序列状态 - 2019年Luca Ferrari的博客文章