System Catalogs Definitions - pg_am - 《Greenplum Database v6.23 Documentation》

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
`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 zero 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		Does the access method support ordered scans sorted by the indexed column’s value?
`amcanorderbyop`	boolean		Does the access method support ordered scans sorted by the result of an operator on the indexed column?
`amcanbackward`	boolean		Does the access method support backward scanning?
`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?
`amsearcharray`	boolean		Does the access method support `ScalarArrayOpExpr` searches?
`amsearchnulls`	boolean		Does the access method support `IS NULL/NOT NULL` searches?
`amstorage`	boolean		Can index storage data type differ from column data type?
`amclusterable`	boolean		Can an index of this type be clustered on?
`ampredlocks`	boolean		Does an index of this type manage fine-grained predicae locks?
`amkeytype`	oid	pg_type.oid	Type of data stored in index, or zero 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 zero if none
`amgetbitmap`	regproc	pg_proc.oid	“Fetch all tuples” function, or zero 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 index supports index-only scans, or zero if none
`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

Parent topic: System Catalogs Definitions