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.

Table 1. pg_catalog.pg_am
column	type	references	description
`amname`	name		Name of the access method
`amstrategies`	int2		Number of operator strategies for this access method
`amsupport`	int2		Number of support routines for this access method
`amorderstrategy`	int2		Zero if the index offers no sort order, otherwise the strategy number of the strategy operator that describes the sort order
`amcanunique`	boolean		Does the access method support unique indexes?
`amcanmulticol`	boolean		Does the access method support multicolumn indexes?
`amoptionalkey`	boolean		Does the access method support a scan without any constraint for the first index column?
`amindexnulls`	boolean		Does the access method support null index entries?
`amstorage`	boolean		Can index storage data type differ from column data type?
`amclusterable`	boolean		Can an index of this type be clustered on?
`aminsert`	regproc	pg_proc.oid	"Insert this tuple" function
`ambeginscan`	regproc	pg_proc.oid	"Start new scan" function
`amgettuple`	regproc	pg_proc.oid	"Next valid tuple" function
`amgetmulti`	regproc	pg_proc.oid	"Fetch multiple tuples" function
`amrescan`	regproc	pg_proc.oid	"Restart this scan" function
`amendscan`	regproc	pg_proc.oid	"End this 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
`ambulkdelete`	regproc	pg_proc.oid	Bulk-delete function
`amvacuumcleanup`	regproc	pg_proc.oid	Post-`VACUUM` cleanup function
`amcostestimate`	regproc	pg_proc.oid	Function to estimate cost of an index scan
`amoptions`	regproc	pg_proc.oid	Function to parse and validate reloptions for an index