pg_am

The pg_am table stores information about index access methods. There is one row for each index access method supported by the system.

Column Type References Description

Column	Type	References	Description
oid	oid	—	Row identifier (hidden attribute; must be explicitly selected)
amname	name	—	Name of the access method
amstrategies	int2	—	Number of operator strategies for this access method, or `0` if the access method does not have a fixed set of operator strategies
amsupport	int2	—	Number of support routines for this access method
amcanorder	boolean	—	Whether the access method supports ordered scans sorted by the indexed column’s value
amcanorderbyop	boolean	—	Whether the access method supports ordered scans sorted by the result of an operator on the indexed column
amcanbackward	boolean	—	Whether the access method supports backward scanning
amcanunique	boolean	—	Whether the access method supports unique indexes
amcanmulticol	boolean	—	Whether the access method supports multicolumn indexes
amoptionalkey	boolean	—	Whether the access method supports a scan without any constraint for the first index column
amsearcharray	boolean	—	Whether the access method supports `ScalarArrayOpExpr` searches
amsearchnulls	boolean	—	Whether the access method supports `IS NULL/NOT NULL` searches
amstorage	boolean	—	Whether the index storage data type can differ from the column data type
amclusterable	boolean	—	Whether an index of this type can be clustered
ampredlocks	boolean	—	Whether an index of this type manages fine-grained predicate locks
amkeytype	oid	pg_type.oid	Type of data stored in index, or `0` if not a fixed type
aminsert	regproc	pg_proc.oid	"Insert this tuple" function
ambeginscan	regproc	pg_proc.oid	"Prepare for index scan" function
amgettuple	regproc	pg_proc.oid	"Next valid tuple" function, or `0` if none
amgetbitmap	regproc	pg_proc.oid	"Fetch all tuples" function, or `0` if none
amrescan	regproc	pg_proc.oid	"(Re)start index scan" function
amendscan	regproc	pg_proc.oid	"Clean up after index scan" function
ammarkpos	regproc	pg_proc.oid	"Mark current scan position" function
amrestrpos	regproc	pg_proc.oid	"Restore marked scan position" function
ambuild	regproc	pg_proc.oid	"Build new index" function
ambuildempty	regproc	pg_proc.oid	"Build empty index" function
ambulkdelete	regproc	pg_proc.oid	Bulk-delete function
amvacuumcleanup	regproc	pg_proc.oid	Post-`VACUUM` cleanup function
amcanreturn	regproc	pg_proc.oid	Function to check whether the index supports index-only scans, or `0` if none
amcostestimate	regproc	pg_proc.oid	Function to estimate the cost of an index scan
amoptions	regproc	pg_proc.oid	Function to parse and validate `reloptions` for an index

oid

—

Row identifier (hidden attribute; must be explicitly selected)

amname

name

—

Name of the access method

amstrategies

int2

—

Number of operator strategies for this access method, or 0 if the access method does not have a fixed set of operator strategies

amsupport

int2

—

Number of support routines for this access method

amcanorder

boolean

—

Whether the access method supports ordered scans sorted by the indexed column’s value

amcanorderbyop

boolean

—

Whether the access method supports ordered scans sorted by the result of an operator on the indexed column

amcanbackward

boolean

—

Whether the access method supports backward scanning

amcanunique

boolean

—

Whether the access method supports unique indexes

amcanmulticol

boolean

—

Whether the access method supports multicolumn indexes

amoptionalkey

boolean

—

Whether the access method supports a scan without any constraint for the first index column

amsearcharray

boolean

—

Whether the access method supports ScalarArrayOpExpr searches

amsearchnulls

boolean

—

Whether the access method supports IS NULL/NOT NULL searches

amstorage

boolean

—

Whether the index storage data type can differ from the column data type

amclusterable

boolean

—

Whether an index of this type can be clustered

ampredlocks

boolean

—

Whether an index of this type manages fine-grained predicate locks

amkeytype

oid

pg_type.oid

Type of data stored in index, or 0 if not a fixed type

aminsert

regproc

pg_proc.oid

"Insert this tuple" function

ambeginscan

regproc

pg_proc.oid

"Prepare for index scan" function

amgettuple

regproc

pg_proc.oid

"Next valid tuple" function, or 0 if none

amgetbitmap

regproc

pg_proc.oid

"Fetch all tuples" function, or 0 if none

amrescan

regproc

pg_proc.oid

"(Re)start index scan" function

amendscan

regproc

pg_proc.oid

"Clean up after index scan" function

ammarkpos

regproc

pg_proc.oid

"Mark current scan position" function

amrestrpos

regproc

pg_proc.oid

"Restore marked scan position" function

ambuild

regproc

pg_proc.oid

"Build new index" function

ambuildempty

regproc

pg_proc.oid

"Build empty index" function

ambulkdelete

regproc

pg_proc.oid

Bulk-delete function

amvacuumcleanup

regproc

pg_proc.oid

Post-VACUUM cleanup function

amcanreturn

regproc

pg_proc.oid

Function to check whether the index supports index-only scans, or 0 if none

amcostestimate

regproc

pg_proc.oid

Function to estimate the cost of an index scan

amoptions

regproc

pg_proc.oid

Function to parse and validate reloptions for an index

pg_aggregate

pg_amop