Object Identifier Types

Object identifiers (OIDs) are used internally by GaussDB as primary keys for various system catalogs. The system does not automatically add an OID column to a table created by a user. The OID type indicates an object identifier. Table 1 describes the OID types.

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.

**Table 1** Object identifier types
Name	Reference	Description	Example
OID	N/A	Numeric object identifier	564182
CID	N/A	Command identifier. This is the data type of the system columns cmin and cmax. Command identifiers are 32-bit quantities.	N/A
XID	N/A	A transaction identifier. This is the data type of the system columns xmin and xmax. Transaction identifiers are 64-bit quantities.	N/A
TID	N/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.	N/A
REGCONFIG	pg_ts_config	Text search configuration	english
REGDICTIONARY	pg_ts_dict	Text search dictionary	simple
REGOPER	pg_operator	Operator name	N/A
REGOPERATOR	pg_operator	Operator with argument types	*(integer,integer) or -(NONE,integer)
REGPROC	pg_proc	Function name	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.

Example:

   
        gaussdb=# 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.

Example:

   
    
      
      
        gaussdb=# SELECT attrelid,attname,atttypid,attstattarget FROM pg_attribute WHERE attrelid = 'pg_type'::REGCLASS;
 attrelid |  attname   | atttypid | attstattarget 
----------+------------+----------+---------------
| xc_node_id     |       23 |             0
| tableoid       |       26 |             0
| cmax           |       29 |             0
| xmax           |       28 |             0
| cmin           |       29 |             0
| xmin           |       28 |             0
| oid            |       26 |             0
| ctid           |       27 |             0
| typname        |       19 |            -1
| typnamespace   |       26 |            -1
| typowner       |       26 |            -1
| typlen         |       21 |            -1
| typbyval       |       16 |            -1
| typtype        |       18 |            -1
| typcategory    |       18 |            -1
| typispreferred |       16 |            -1
| typisdefined   |       16 |            -1
| typdelim       |       18 |            -1
| typrelid       |       26 |            -1
| typelem        |       26 |            -1
| typarray       |       26 |            -1
| typinput       |       24 |            -1
| typoutput      |       24 |            -1
| typreceive     |       24 |            -1
| typsend        |       24 |            -1
| typmodin       |       24 |            -1
| typmodout      |       24 |            -1
| typanalyze     |       24 |            -1
| typalign       |       18 |            -1
| typstorage     |       18 |            -1
| typnotnull     |       16 |            -1
| typbasetype    |       26 |            -1
| typtypmod      |       23 |            -1
| typndims       |       23 |            -1
| typcollation   |       26 |            -1
| typdefaultbin  |      194 |            -1
| typdefault     |       25 |            -1
| typacl         |     1034 |            -1
| typelemmod     |       23 |            -1
(39 rows)

       

     

   
  