pg_am

一个系统目录表，存储有关关系访问方法的信息

**pg_am** 是一个系统目录表，存储有关关系访问方法的信息。

在 PostgreSQL 11 及更早版本中，这些仅限于索引访问方法；PostgreSQL 12 添加了对表访问方法的支持。

从下面的更改历史记录可以看出，随着需要添加新的索引属性，这个目录表经常发生更改。在 PostgreSQL 9.6 中，该表得到了极大的简化，现在可以通过诸如 pg_index_column_has_property() 之类的函数查询索引属性。

按 PostgreSQL 版本定义

pg_am (PostgreSQL 18)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 oid       | oid     |           | not null | 
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_oid_index" PRIMARY KEY, btree (oid)
    "pg_am_name_index" UNIQUE CONSTRAINT, btree (amname)

**文档**: pg_am

pg_am (PostgreSQL 17)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 oid       | oid     |           | not null | 
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_oid_index" PRIMARY KEY, btree (oid)
    "pg_am_name_index" UNIQUE CONSTRAINT, btree (amname)

**文档**: pg_am

pg_am (PostgreSQL 16)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 oid       | oid     |           | not null | 
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_oid_index" PRIMARY KEY, btree (oid)
    "pg_am_name_index" UNIQUE CONSTRAINT, btree (amname)

**文档**: pg_am

pg_am (PostgreSQL 15)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 oid       | oid     |           | not null | 
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_oid_index" PRIMARY KEY, btree (oid)
    "pg_am_name_index" UNIQUE CONSTRAINT, btree (amname)

**文档**: pg_am

pg_am (PostgreSQL 14)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 oid       | oid     |           | not null | 
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_oid_index" PRIMARY KEY, btree (oid)
    "pg_am_name_index" UNIQUE CONSTRAINT, btree (amname)

**文档**: pg_am

pg_am (PostgreSQL 13)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 oid       | oid     |           | not null | 
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 12)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 oid       | oid     |           | not null | 
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 11)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 10)

               Table "pg_catalog.pg_am"
  Column   |  Type   | Collation | Nullable | Default 
-----------+---------+-----------+----------+---------
 amname    | name    |           | not null | 
 amhandler | regproc |           | not null | 
 amtype    | "char"  |           | not null | 
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 9.6)

    Table "pg_catalog.pg_am"
  Column   |  Type   | Modifiers 
-----------+---------+-----------
 amname    | name    | not null
 amhandler | regproc | not null
 amtype    | "char"  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 9.5)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanorderbyop  | boolean  | not null
 amcanbackward   | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amsearcharray   | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 ampredlocks     | boolean  | not null
 amkeytype       | oid      | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetbitmap     | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambuildempty    | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcanreturn     | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 9.4)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanorderbyop  | boolean  | not null
 amcanbackward   | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amsearcharray   | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 ampredlocks     | boolean  | not null
 amkeytype       | oid      | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetbitmap     | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambuildempty    | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcanreturn     | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 9.3)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanorderbyop  | boolean  | not null
 amcanbackward   | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amsearcharray   | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 ampredlocks     | boolean  | not null
 amkeytype       | oid      | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetbitmap     | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambuildempty    | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcanreturn     | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 9.2)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanorderbyop  | boolean  | not null
 amcanbackward   | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amsearcharray   | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 ampredlocks     | boolean  | not null
 amkeytype       | oid      | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetbitmap     | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambuildempty    | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcanreturn     | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 9.1)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanorderbyop  | boolean  | not null
 amcanbackward   | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 ampredlocks     | boolean  | not null
 amkeytype       | oid      | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetbitmap     | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambuildempty    | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 9.0)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanbackward   | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amindexnulls    | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 amkeytype       | oid      | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetbitmap     | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 8.4)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanbackward   | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amindexnulls    | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 amkeytype       | oid      | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetbitmap     | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 8.3)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amcanorder      | boolean  | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amindexnulls    | boolean  | not null
 amsearchnulls   | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetmulti      | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

pg_am (PostgreSQL 8.2)

        Table "pg_catalog.pg_am"
     Column      |   Type   | Modifiers 
-----------------+----------+-----------
 amname          | name     | not null
 amstrategies    | smallint | not null
 amsupport       | smallint | not null
 amorderstrategy | smallint | not null
 amcanunique     | boolean  | not null
 amcanmulticol   | boolean  | not null
 amoptionalkey   | boolean  | not null
 amindexnulls    | boolean  | not null
 amstorage       | boolean  | not null
 amclusterable   | boolean  | not null
 aminsert        | regproc  | not null
 ambeginscan     | regproc  | not null
 amgettuple      | regproc  | not null
 amgetmulti      | regproc  | not null
 amrescan        | regproc  | not null
 amendscan       | regproc  | not null
 ammarkpos       | regproc  | not null
 amrestrpos      | regproc  | not null
 ambuild         | regproc  | not null
 ambulkdelete    | regproc  | not null
 amvacuumcleanup | regproc  | not null
 amcostestimate  | regproc  | not null
 amoptions       | regproc  | not null
Indexes:
    "pg_am_name_index" UNIQUE, btree (amname)
    "pg_am_oid_index" UNIQUE, btree (oid)

**文档**: pg_am

更改历史

PostgreSQL 12
- 添加了对表访问方法的支持，这意味着列 amtype 可以同时包含 i 和 t (提交 8586bf7e)
PostgreSQL 9.6
- 删除了以下列 (提交 65c5fcd3) 并替换为 SQL 可访问的函数 (提交 ed0097e4)
  - amstrategies
  - amsupport
  - amcanorder
  - amcanorderbyop
  - amcanbackward
  - amcanunique
  - amcanmulticol
  - amoptionalkey
  - amsearcharray
  - amsearchnulls
  - amstorage
  - amclusterable
  - ampredlocks
  - amkeytype
  - aminsert
  - ambeginscan
  - amgettuple
  - amgetbitmap
  - amrescan
  - amendscan
  - ammarkpos
  - amrestrpos
  - ambuild
  - ambuildempty
  - ambulkdelete
  - amvacuumcleanup
  - amcanreturn
  - amcostestimate
  - amoptions
- 添加了列 amhandler (提交 65c5fcd3)
PostgreSQL 9.2
- 添加了列 amsearcharray (提交 9e8da0f7)
- 添加了列 amcanreturn (初始提交 a2822fb9)
PostgreSQL 9.1
- 添加了列 ampredlocks (提交 dafaa3ef)
- 添加了列 ambuildempty (提交 7e2f9062)
- 删除了列 amindexnulls (提交 7e2f9062)
PostgreSQL 8.4
- 添加了列 amcanbackward (提交 e4fb8ff0)
- 添加了列 amkeytype (提交 4adc2f72)
PostgreSQL 8.3
- 添加了列 amsearchnulls (提交 f02a82b6)
PostgreSQL 8.2
- 添加了列 amstorage (提交 e5734597)
- 添加了列 amclusterable (提交 e5734597)
- 删除了列 amconcurrent (提交 09d3670d)
PostgreSQL 8.1
- 添加了列 amgettuple (提交 bf3dbb58)
- 添加了列 amgetmulti (提交 bf3dbb58)
- 删除了列 amowner (提交 bf3dbb58)
PostgreSQL 7.4
- 添加了列 amvacuumcleanup (提交 799bc58d)

**注意**: 此列表不包含早于 PostgreSQL 7.3 的任何更改

示例

PostgreSQL 12 中的默认值

postgres=# SELECT * FROM pg_am;
 oid  | amname |      amhandler       | amtype
------+--------+----------------------+--------
    2 | heap   | heap_tableam_handler | t
  403 | btree  | bthandler            | i
  405 | hash   | hashhandler          | i
  783 | gist   | gisthandler          | i
 2742 | gin    | ginhandler           | i
 4000 | spgist | spghandler           | i
 3580 | brin   | brinhandler          | i
(7 rows)

参考文献

PostgreSQL 文档： pg_am

参见

default_table_access_method，pg_amop，pg_amproc，pg_index_column_has_property()，pg_index_has_property()，pg_indexam_has_property()

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提交任何关于 "pg_am" 的评论、建议或更正 在此。

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目录

pg_am

按 PostgreSQL 版本定义

pg_am (PostgreSQL 18)

pg_am (PostgreSQL 17)

pg_am (PostgreSQL 16)

pg_am (PostgreSQL 15)

pg_am (PostgreSQL 14)

pg_am (PostgreSQL 13)

pg_am (PostgreSQL 12)

pg_am (PostgreSQL 11)

pg_am (PostgreSQL 10)

pg_am (PostgreSQL 9.6)

pg_am (PostgreSQL 9.5)

pg_am (PostgreSQL 9.4)

pg_am (PostgreSQL 9.3)

pg_am (PostgreSQL 9.2)

pg_am (PostgreSQL 9.1)

pg_am (PostgreSQL 9.0)

pg_am (PostgreSQL 8.4)

pg_am (PostgreSQL 8.3)

pg_am (PostgreSQL 8.2)

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示例

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