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
