PG_AM
PG_AM records information about index access methods. There is one row for each index access method supported by the system.
Table 1 PG_AM columns
Name | Type | Reference | Description |
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amname | name | - | Name of the access method |
amstrategies | smallint | - | Number of operator strategies for the access method (0 if the access method does not have a fixed set of operator strategies) |
amsupport | smallint | - | Number of support routines for the 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 scanning 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 the index storage data type can differ from the 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 (0 if it is not a fixed type) |
aminsert | regproc | PG_PROC.proname | "Insert this tuple" function |
ambeginscan | regproc | PG_PROC.proname | "Prepare for index scan" function |
amgettuple | regproc | PG_PROC.proname | "Next valid tuple" function (0 if none) |
amgetbitmap | regproc | PG_PROC.proname | "Fetch all valid tuples" function (0 if none) |
amrescan | regproc | PG_PROC.proname | "(Re)start index scan" function |
amendscan | regproc | PG_PROC.proname | "Clean up after index scan" function |
ammarkpos | regproc | PG_PROC.proname | "Mark current scan position" function |
amrestrpos | regproc | PG_PROC.proname | "Restore marked scan position" function |
ammerge | regproc | PG_PROC.proname | "Merge multiple indexes" function |
ambuild | regproc | PG_PROC.proname | "Build new index" function |
ambuildempty | regproc | PG_PROC.proname | "Build empty index" function |
ambulkdelete | regproc | PG_PROC.proname | Bulk-delete function |
amvacuumcleanup | regproc | PG_PROC.proname | Post-VACUUM cleanup function |
amcanreturn | regproc | PG_PROC.proname | Function to check whether the index supports index-only scans (0 if none) |
amcostestimate | regproc | PG_PROC.proname | Function to estimate cost of an index scan |
amoptions | regproc | PG_PROC.proname | Function to parse and validate reloptions for an index |
openGauss 2024-09-07 00:58:25