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42.3. pg_am

The catalog pg_am stores information about index access methods. There is one row for each index access method supported by the system. The contents of this catalog are discussed in detail in Chapter 48.

Table 42-3. pg_am Columns

NameTypeReferencesDescription
amnamename Name of the access method
amstrategiesint2 Number of operator strategies for this access method
amsupportint2 Number of support routines for this access method
amorderstrategyint2 Zero if the index offers no sort order, otherwise the strategy number of the strategy operator that describes the sort order
amcanuniquebool Does the access method support unique indexes?
amcanmulticolbool Does the access method support multicolumn indexes?
amoptionalkeybool Does the access method support a scan without any constraint for the first index column?
amindexnullsbool Does the access method support null index entries?
amconcurrentbool Does the access method support concurrent updates?
aminsertregprocpg_proc.oid"Insert this tuple" function
ambeginscanregprocpg_proc.oid"Start new scan" function
amgettupleregprocpg_proc.oid"Next valid tuple" function
amgetmultiregprocpg_proc.oid"Fetch multiple tuples" function
amrescanregprocpg_proc.oid"Restart this scan" function
amendscanregprocpg_proc.oid"End this scan" function
ammarkposregprocpg_proc.oid"Mark current scan position" function
amrestrposregprocpg_proc.oid"Restore marked scan position" function
ambuildregprocpg_proc.oid"Build new index" function
ambulkdeleteregprocpg_proc.oidBulk-delete function
amvacuumcleanupregprocpg_proc.oidPost-VACUUM cleanup function
amcostestimateregprocpg_proc.oidFunction to estimate cost of an index scan