PG_AM¶
PG_AM records information about index access methods. There is one row for each index access method supported by the system.
Column | Type | Reference | Description |
|---|---|---|---|
OID | OID |
| Row identifier (hidden attribute; displayed only when explicitly selected). |
amname | Name |
| Name of the access method. |
amstrategies | Smallint |
| Number of operator strategies for this access method, or zero if access method does not have a fixed set of operator strategies. |
amsupport | Smallint |
| Number of support routines for this access method. |
amcanorder | boolean |
| Whether the access method supports ordered scans sorted by the indexed column's value. |
amcanorderbyop | boolean |
| Whether the access method supports ordered scans sorted by the result of an operator on the indexed column. |
amcanbackward | boolean |
| Whether the access method supports backward scanning. |
amcanunique | boolean |
| Whether the access method supports unique indexes. |
amcanmulticol | boolean |
| Whether the access method supports multi-column indexes. |
amoptionalkey | boolean |
| Whether the access method supports a scan without any constraint for the first index column. |
amsearcharray | boolean |
| Whether the access method supports ScalarArrayOpExpr searches. |
amsearchnulls | boolean |
| Whether the access method supports IS NULL/NOT NULL searches. |
amstorage | boolean |
| Whether an index storage data type can differ from a column data type. |
amclusterable | boolean |
| Whether an index of this type can be clustered on. |
ampredlocks | boolean |
| Whether an index of this type manages fine-grained predicate 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 valid 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. |
ammerge | regproc | PG_PROC.oid | "Merge multiple indexes" 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. |