Object Identifier Types¶
Object identifiers (OIDs) are used internally by GaussDB(DWS) as primary keys for various system catalogs. OIDs are not added to user-created tables by the system. The OID type represents an object identifier.
The OID type is currently implemented as an unsigned four-byte integer. So, using a user-created table's OID column as a primary key is discouraged.
Name | Reference | Description | Examples |
|---|---|---|---|
OID |
| Numeric object identifier | 564182 |
CID |
| A command identifier. This is the data type of the system columns cmin and cmax. Command identifiers are 32-bit quantities. |
|
XID |
| A transaction identifier. This is the data type of the system columns xmin and xmax. Transaction identifiers are also 32-bit quantities. |
|
TID |
| A row identifier. This is the data type of the system column ctid. A row ID is a pair (block number, tuple index within block) that identifies the physical location of the row within its table. |
|
REGCONFIG | pg_ts_config | Text search configuration | english |
REGDICTIONARY | pg_ts_dict | Text search dictionary | simple |
REGOPER | pg_operator | Operator name | |
REGOPERATOR | pg_operator | Operator with argument types | *(integer,integer) or -(NONE,integer) |
REGPROC | pg_proc | Indicates the name of the function. | sum |
REGPROCEDURE | pg_proc | Function with argument types | sum(int4) |
REGCLASS | pg_class | Relation name | pg_type |
REGTYPE | pg_type | Data type name | integer |
The OID type is used for a column in the database system catalog.
For example:
SELECT oid FROM pg_class WHERE relname = 'pg_type';
oid
------
1247
(1 row)
The alias type for OID is REGCLASS which allows simplified search for OID values.
For example:
SELECT attrelid,attname,atttypid,attstattarget FROM pg_attribute WHERE attrelid = 'pg_type'::REGCLASS;
attrelid | attname | atttypid | attstattarget
----------+----------------+----------+---------------
1247 | xc_node_id | 23 | 0
1247 | tableoid | 26 | 0
1247 | cmax | 29 | 0
1247 | xmax | 28 | 0
1247 | cmin | 29 | 0
1247 | xmin | 28 | 0
1247 | oid | 26 | 0
1247 | ctid | 27 | 0
1247 | typname | 19 | -1
1247 | typnamespace | 26 | -1
1247 | typowner | 26 | -1
1247 | typlen | 21 | -1
1247 | typbyval | 16 | -1
1247 | typtype | 18 | -1
1247 | typcategory | 18 | -1
1247 | typispreferred | 16 | -1
1247 | typisdefined | 16 | -1
1247 | typdelim | 18 | -1
1247 | typrelid | 26 | -1
1247 | typelem | 26 | -1
1247 | typarray | 26 | -1
1247 | typinput | 24 | -1
1247 | typoutput | 24 | -1
1247 | typreceive | 24 | -1
1247 | typsend | 24 | -1
1247 | typmodin | 24 | -1
1247 | typmodout | 24 | -1
1247 | typanalyze | 24 | -1
1247 | typalign | 18 | -1
1247 | typstorage | 18 | -1
1247 | typnotnull | 16 | -1
1247 | typbasetype | 26 | -1
1247 | typtypmod | 23 | -1
1247 | typndims | 23 | -1
1247 | typcollation | 26 | -1
1247 | typdefaultbin | 194 | -1
1247 | typdefault | 25 | -1
1247 | typacl | 1034 | -1
(38 rows)