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

Name	Type	Reference	Description
amname	name	-	Name of the access method
amstrategies	smallint	-	Number of operator strategies for the access method (0 if the access method does not have a fixed set of operator strategies)
amsupport	smallint	-	Number of support routines for the 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 scanning 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 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 (0 if it is not a fixed type)
aminsert	regproc	PG_PROC.proname	"Insert this tuple" function
ambeginscan	regproc	PG_PROC.proname	"Prepare for index scan" function
amgettuple	regproc	PG_PROC.proname	"Next valid tuple" function (0 if none)
amgetbitmap	regproc	PG_PROC.proname	"Fetch all valid tuples" function (0 if none)
amrescan	regproc	PG_PROC.proname	"(Re)start index scan" function
amendscan	regproc	PG_PROC.proname	"Clean up after index scan" function
ammarkpos	regproc	PG_PROC.proname	"Mark current scan position" function
amrestrpos	regproc	PG_PROC.proname	"Restore marked scan position" function
ammerge	regproc	PG_PROC.proname	"Merge multiple indexes" function
ambuild	regproc	PG_PROC.proname	"Build new index" function
ambuildempty	regproc	PG_PROC.proname	"Build empty index" function
ambulkdelete	regproc	PG_PROC.proname	Bulk-delete function
amvacuumcleanup	regproc	PG_PROC.proname	Post-VACUUM cleanup function
amcanreturn	regproc	PG_PROC.proname	Function to check whether the index supports index-only scans (0 if none)
amcostestimate	regproc	PG_PROC.proname	Function to estimate cost of an index scan
amoptions	regproc	PG_PROC.proname	Function to parse and validate reloptions for an index