SYSTEM CATALOG · System catalog

pg_am

PostgreSQL documentation ↗Source definition ↗

The catalog pg_am stores information about relation access methods. There is one row for each access method supported by the system. Currently, only tables and indexes have access methods. The requirements for table and index access methods are discussed in detail in Chapter 62 and Chapter 63 respectively.

First seen PG 9.0Last seen PG 19Columns 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

Checked column by column against a PostgreSQL 18.6 instance · Raw measurement record ↗

Columns PostgreSQL 18

pg_am

COLUMN	TYPE	DESCRIPTION
`oid`	`oid`NOT NULL	Row identifier
`amname`	`name`NOT NULL	Name of the access method
`amhandler`	`regproc`NOT NULL	OID of a handler function that is responsible for supplying information about the access methodReferences:`pg_proc.oid`
`amtype`	`"char"`NOT NULLDocumented as:`char`	t = table (including materialized views), i = index.

Columns marked "implicit" are not included in SELECT *; some early statistics views are completed from same-version source, and the extra provenance is shown in the column description.

Common system columns 6

System attributes PostgreSQL provides, normally not expanded by SELECT *. Kept separately so they are not mixed in with ordinary columns.

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

Column evolution matrix

Hover a cell for the column type

PresentAdded / type or attribute changeRemoved

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`
`amname`
`amstrategies`							−	–	–	–	–	–	–	–	–	–	–
`amsupport`							−	–	–	–	–	–	–	–	–	–	–
`amcanorder`							−	–	–	–	–	–	–	–	–	–	–
`amcanbackward`							−	–	–	–	–	–	–	–	–	–	–
`amcanunique`							−	–	–	–	–	–	–	–	–	–	–
`amcanmulticol`							−	–	–	–	–	–	–	–	–	–	–
`amoptionalkey`							−	–	–	–	–	–	–	–	–	–	–
`amindexnulls`		−	–	–	–	–	–	–	–	–	–	–	–	–	–	–	–
`amsearchnulls`							−	–	–	–	–	–	–	–	–	–	–
`amstorage`							−	–	–	–	–	–	–	–	–	–	–
`amclusterable`							−	–	–	–	–	–	–	–	–	–	–
`amkeytype`							−	–	–	–	–	–	–	–	–	–	–
`aminsert`							−	–	–	–	–	–	–	–	–	–	–
`ambeginscan`							−	–	–	–	–	–	–	–	–	–	–
`amgettuple`							−	–	–	–	–	–	–	–	–	–	–
`amgetbitmap`							−	–	–	–	–	–	–	–	–	–	–
`amrescan`							−	–	–	–	–	–	–	–	–	–	–
`amendscan`							−	–	–	–	–	–	–	–	–	–	–
`ammarkpos`							−	–	–	–	–	–	–	–	–	–	–
`amrestrpos`							−	–	–	–	–	–	–	–	–	–	–
`ambuild`							−	–	–	–	–	–	–	–	–	–	–
`ambulkdelete`							−	–	–	–	–	–	–	–	–	–	–
`amvacuumcleanup`							−	–	–	–	–	–	–	–	–	–	–
`amcostestimate`							−	–	–	–	–	–	–	–	–	–	–
`amoptions`							−	–	–	–	–	–	–	–	–	–	–
`amcanorderbyop`	–						−	–	–	–	–	–	–	–	–	–	–
`ampredlocks`	–						−	–	–	–	–	–	–	–	–	–	–
`ambuildempty`	–						−	–	–	–	–	–	–	–	–	–	–
`amsearcharray`	–	–					−	–	–	–	–	–	–	–	–	–	–
`amcanreturn`	–	–					−	–	–	–	–	–	–	–	–	–	–
`amhandler`	–	–	–	–	–	–
`amtype`	–	–	–	–	–	–

9.0 is the coverage baseline; a column already present in the baseline is not marked as added. The matrix aligns columns by name, so a rename appears as the old column removed and a new column added.

Evolution timeline

Changes between adjacent majors

PostgreSQL 18 ← 17

Catalog description updated

PostgreSQL 17 ← 16

Catalog description updated

PostgreSQL 15 ← 14

Catalog description updated

PostgreSQL 14 ← 13

Catalog description updated

PostgreSQL 12 ← 11

~ oid: implicit → ordinary2 column description updatesCatalog description updated

PostgreSQL 11 ← 10

Catalog description updated

PostgreSQL 10 ← 9.6

Catalog description updated

PostgreSQL 9.6 ← 9.5

+ amhandler+ amtype− 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− amoptionsCatalog description updated

PostgreSQL 9.5 ← 9.4

1 column description updatesCatalog description updated

PostgreSQL 9.4 ← 9.3

Catalog description updated

PostgreSQL 9.3 ← 9.2

1 column description updatesCatalog description updated

PostgreSQL 9.2 ← 9.1

+ amsearcharray+ amcanreturn

PostgreSQL 9.1 ← 9.0

+ amcanorderbyop+ ampredlocks+ ambuildempty− amindexnulls4 column description updatesCatalog description updated

Compare any two versions

FROMTOInclude description updates

Pick two versions to see added, removed, and retyped columns. The interactive comparison needs JavaScript; the evolution timeline reads fine without it.