# pg_am

The `pg_am` table stores information about index access methods. There is one row for each index access method supported by the system.



Table 1. `pg_catalog.pg_am`

| column            | type     | references  | description                                                  |
| :---------------- | :------- | :---------- | :----------------------------------------------------------- |
| `amname`          | name     |             | Name of the access method                                    |
| `amstrategies`    | smallint |             | Number of operator strategies for this access method         |
| `amsupport`       | smallint |             | Number of support routines for this access method            |
| `amorderstrategy` | smallint |             | Zero if the index offers no sort order, otherwise the strategy number of the strategy operator that describes the sort order |
| `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? |
| `amindexnulls`    | boolean  |             | Does the access method support null index entries?           |
| `amstorage`       | boolean  |             | Can index storage data type differ from column data type?    |
| `amclusterable`   | boolean  |             | Can an index of this type be clustered on?                   |
| `amcanshrink`     | boolean  |             | Can an index of this type be shrinked?                       |
| `aminsert`        | regproc  | pg_proc.oid | “Insert this tuple” function                                 |
| `ambeginscan`     | regproc  | pg_proc.oid | “Start new scan” function                                    |
| `amgettuple`      | regproc  | pg_proc.oid | “Next valid tuple” function                                  |
| `amgetmulti`      | regproc  | pg_proc.oid | “Fetch multiple tuples” function                             |
| `amrescan`        | regproc  | pg_proc.oid | “Restart this scan” function                                 |
| `amendscan`       | regproc  | pg_proc.oid | “End this 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                                   |
| `ambulkdelete`    | regproc  | pg_proc.oid | Bulk-delete function                                         |
| `amvacuumcleanup` | regproc  | pg_proc.oid | Post-`VACUUM` cleanup function                               |
| `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       |