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
oid	oid	-	Row identifier (hidden attribute, which must be specified).
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	-	Specifies whether the access method supports ordered scans sorted by the indexed column's value. t (true): supported. f (false): not supported.
amcanorderbyop	boolean	-	Specifies whether the access method supports ordered scans sorted by the result of an operator on the indexed column. t (true): supported. f (false): not supported.
amcanbackward	boolean	-	Specifies whether the access method supports backward scanning. t (true): supported. f (false): not supported.
amcanunique	boolean	-	Specifies whether the access method supports unique indexes. t (true): supported. f (false): not supported.
amcanmulticol	boolean	-	Specifies whether the access method supports multi-column indexes. t (true): supported. f (false): not supported.
amoptionalkey	boolean	-	Specifies whether the access method supports scanning without any constraint for the first index column. t (true): supported. f (false): not supported.
amsearcharray	boolean	-	Specifies whether the access method supports ScalarArrayOpExpr searches. t (true): supported. f (false): not supported.
amsearchnulls	boolean	-	Specifies whether the access method supports IS NULL/NOT NULL searches. t (true): supported. f (false): not supported.
amstorage	boolean	-	Specifies whether the index storage data type can differ from the column data type. t (true): same. f (false): different.
amclusterable	boolean	-	Specifies whether an index of this type can be clustered on. t (true): allowed. f (false): not allowed.
ampredlocks	boolean	-	Specifies whether an index of this type manages fine-grained predicate locks. t (true): allowed. f (false): not allowed.
amkeytype	oid	oid in PG_TYPE	Type of data stored in index (0 if it is not a fixed type)
aminsert	regproc	proname in PG_PROC	"Insert this tuple" function
ambeginscan	regproc	proname in PG_PROC	"Prepare for index scan" function
amgettuple	regproc	proname in PG_PROC	"Next valid tuple" function (0 if none)
amgetbitmap	regproc	proname in PG_PROC	"Fetch all valid tuples" function (0 if none)
amrescan	regproc	proname in PG_PROC	"(Re)start index scan" function
amendscan	regproc	proname in PG_PROC	"Clean up after index scan" function
ammarkpos	regproc	proname in PG_PROC	"Mark current scan position" function
amrestrpos	regproc	proname in PG_PROC	"Restore marked scan position" function
ammerge	regproc	proname in PG_PROC	"Merge multiple indexes" function
ambuild	regproc	proname in PG_PROC	"Build new index" function
ambuildempty	regproc	proname in PG_PROC	"Build empty index" function
ambulkdelete	regproc	proname in PG_PROC	Bulk-delete function
amvacuumcleanup	regproc	proname in PG_PROC	Post-VACUUM cleanup function
amcanreturn	regproc	proname in PG_PROC	Function to check whether the index supports index-only scans (0 if none)
amcostestimate	regproc	proname in PG_PROC	Function to estimate cost of an index scan
amoptions	regproc	proname in PG_PROC	Function to parse and validate reloptions for an index