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