PG_AM

PG_AM records information about index access methods. There is one row for each index access method supported by the system.

**Table 1** PG_AM columns
Column	Type	Reference	Description
OID	OID	-	Row identifier (hidden attribute; displayed only when explicitly selected).
amname	Name	-	Name of the access method.
amstrategies	Smallint	-	Number of operator strategies for this access method, or zero if access method does not have a fixed set of operator strategies.
amsupport	Smallint	-	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 multi-column 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 an index storage data type can differ from a column data type.
amclusterable	boolean	-	Whether an index of this type can be clustered on.
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 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 valid 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.
ammerge	regproc	PG_PROC.oid	"Merge multiple indexes" 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.