42
DBMS_ROWID

The DBMS_ROWID package lets you create ROWIDs and get information about ROWIDs from PL/SQL programs and SQL statements. You can find the data block number, the object number, and other components of the ROWID without having to write code to interpret the base-64 character external ROWID.

Usage Notes

Some of the functions in this package take a single parameter: a ROWID. This can be a character or a PL/SLQ ROWID, either restricted or extended, as required.

You can call the DBMS_ROWID functions and procedures from PL/SQL code, and you can also use the functions in SQL statements.

You can use functions from the DBMS_ROWID package just like any built-in SQL function; in other words, you can use them wherever an expression can be used. In this example, the ROWID_BLOCK_NUMBER function is used to return just the block number of a single row in the EMP table:

SELECT dbms_rowid.rowid_block_number(rowid)
     
FROM emp 
WHERE ename = 'KING';

         

PL/SQL Example

This example returns the ROWID for a row in the EMP table, extracts the data object number from the ROWID, using the ROWID_OBJECT function in the DBMS_ROWID package, then displays the object number:

DECLARE
  object_no   INTEGER;
  row_id      ROWID;
  ...
BEGIN
  SELECT ROWID INTO row_id FROM emp
    WHERE empno = 7499;
  object_no := dbms_rowid.rowid_object(row_id);
  dbms_output.put_line('The obj. # is '|| object_no);
  ...

Requirements

This package runs with the privileges of calling user, rather than the package owner ('sys').

ROWID Types

RESTRICTED	Restricted ROWID
EXTENDED	Extended ROWID

For example:

rowid_type_restricted constant integer := 0;
rowid_type_extended   constant integer := 1;

ROWID Verification Results

VALID	Valid ROWID
INVALID	Invalid ROWID

For example:

rowid_is_valid   constant integer := 0;
rowid_is_invalid constant integer := 1;

Object Types

UNDEFINED

Object Number not defined (for restricted ROWIDs)

For example:

rowid_object_undefined constant integer := 0;

ROWID Conversion Types

INTERNAL	Convert to/from column of ROWID type
EXTERNAL	Convert to/from string format

For example:

rowid_convert_internal constant integer := 0;
rowid_convert_external constant integer := 1;

Exceptions

ROWID_INVALID	Invalid rowid format
ROWID_BAD_BLOCK	Block is beyond end of file

For example:

ROWID_INVALID exception;
   pragma exception_init(ROWID_INVALID, -1410);

ROWID_BAD_BLOCK exception;
   pragma exception_init(ROWID_BAD_BLOCK, -28516);

Summary of Subprograms

Table 42-1 DBMS_ROWID Package Subprograms

ROWID_CREATE function

ROWID_INFO procedure

ROWID_TYPE function

ROWID_OBJECT function

ROWID_RELATIVE_FNO function

ROWID_BLOCK_NUMBER function

ROWID_ROW_NUMBER function

ROWID_TO_ABSOLUTE_FNO 
function

ROWID_TO_EXTENDED function

ROWID_TO_RESTRICTED function

ROWID_VERIFY function

ROWID_CREATE function

This function lets you create a ROWID, given the component parts as parameters.

This is useful for testing ROWID operations, because only the Oracle Server can create a valid ROWID that points to data in a database.

Syntax

DBMS_ROWID.ROWID_CREATE (
   rowid_type    IN NUMBER, 
   object_number IN NUMBER,
   relative_fno  IN NUMBER,
   block_number  IN NUMBER,
   row_number    IN NUMBER) 
  RETURN ROWID;

Pragmas

pragma RESTRICT_REFERENCES(rowid_create,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-2 ROWID_CREATE Function Parameters

rowid_type

object_number

relative_fno

block_number

file_number

Example

Create a dummy extended ROWID:

my_rowid := DBMS_ROWID.ROWID_CREATE(1, 9999, 12, 1000, 13);
     


         

Find out what the rowid_object function returns:

obj_number := DBMS_ROWID.ROWID_OBJECT(my_rowid);
     


         

The variable obj_number now contains 9999.

ROWID_INFO procedure

This procedure returns information about a ROWID, including its type (restricted or extended), and the components of the ROWID. This is a procedure, and it cannot be used in a SQL statement.

Syntax

DBMS_ROWID.ROWID_INFO (
   rowid_in         IN   ROWID,
   rowid_type       OUT  NUMBER,
   object_number    OUT  NUMBER,
   relative_fno     OUT  NUMBER,
   block_number     OUT  NUMBER,
   row_number       OUT  NUMBER);

Pragmas

pragma RESTRICT_REFERENCES(rowid_info,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-3 ROWID_INFO Procedure Parameters

rowid_in

rowid_type

object_number

relative_fno

block_number

file_number

Example

This example reads back the values for the ROWID that you created in the ROWID_CREATE:

DBMS_ROWID.ROWID_INFO(my_rowid, rid_type, obj_num,
  file_num, block_num, row_num);

DBMS_OUTPUT.PUT_LINE('The type is ' || rid_type);
DBMS_OUTPUT.PUT_LINE('Data object number is ' || obj_num);
-- and so on...

ROWID_TYPE function

This function returns 0 if the ROWID is a restricted ROWID, and 1 if it is extended.

Syntax

DBMS_ROWID.ROWID_TYPE (
   rowid_id IN ROWID)
  RETURN NUMBER;

Pragmas

pragma RESTRICT_REFERENCES(rowid_type,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-4 ROWID_TYPE Function Parameters

row_id

Example

IF DBMS_ROWID.ROWID_TYPE(my_rowid) = 1 THEN
     
my_obj_num := DBMS_ROWID.ROWID_OBJECT(my_rowid);

         

ROWID_OBJECT function

This function returns the data object number for an extended ROWID. The function returns zero if the input ROWID is a restricted ROWID.

Syntax

DBMS_ROWID.ROWID_OBJECT (
   rowid_id IN ROWID)
  RETURN NUMBER;

Pragmas

pragma RESTRICT_REFERENCES(rowid_object,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-5 ROWID_OBJECT Function Parameters

row_id

Example

SELECT dbms_rowid.rowid_object(ROWID)
     
FROM emp
WHERE empno = 7499;

         

ROWID_RELATIVE_FNO function

This function returns the relative file number of the ROWID specified as the IN parameter. (The file number is relative to the tablespace.)

Syntax

DBMS_ROWID.ROWID_RELATIVE_FNO (
   rowid_id IN ROWID)
  RETURN NUMBER;

Pragmas

pragma RESTRICT_REFERENCES(rowid_relative_fno,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-6 ROWID_RELATIVE_FNO Function Parameters

row_id

Example

The example PL/SQL code fragment returns the relative file number:

DECLARE
     
file_number    INTEGER;
rowid_val      ROWID;

     BEGIN
     
SELECT ROWID INTO rowid_val
  FROM dept 
  WHERE loc = 'Boston';
file_number :=
  dbms_rowid.rowid_relative_fno(rowid_val);
...

         

ROWID_BLOCK_NUMBER function

This function returns the database block number for the input ROWID.

Syntax

DBMS_ROWID.ROWID_BLOCK_NUMBER (
   row_id IN ROWID)
  RETURN NUMBER;

Pragmas

pragma RESTRICT_REFERENCES(rowid_block_number,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-7 ROWID_BLOCK_NUMBER Function Parameters

row_id

Example

The example SQL statement selects the block number from a ROWID and inserts it into another table:

INSERT INTO T2 (SELECT dbms_rowid.rowid_block_number(ROWID)
     
FROM some_table 
WHERE key_value = 42);

         

ROWID_ROW_NUMBER function

This function extracts the row number from the ROWID IN parameter.

Syntax

DBMS_ROWID.ROWID_ROW_NUMBER (
   row_id IN ROWID)
  RETURN NUMBER;

Pragmas

pragma RESTRICT_REFERENCES(rowid_row_number,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-8 ROWID_ROW_NUMBER Function Parameters

row_id

Example

Select a row number:

SELECT dbms_rowid.rowid_row_number(ROWID) 
     
FROM emp
WHERE ename = 'ALLEN';

         

ROWID_TO_ABSOLUTE_FNO function

This function extracts the absolute file number from a ROWID, where the file number is absolute for a row in a given schema and table. The schema name and the name of the schema object (such as a table name) are provided as IN parameters for this function.

Syntax

DBMS_ROWID.ROWID_TO_ABSOLUTE_FNO (
   row_id      IN ROWID,
   schema_name IN VARCHAR2,
   object_name IN VARCHAR2)
  RETURN NUMBER;

Pragmas

pragma RESTRICT_REFERENCES(rowid_to_absolute_fno,WNDS,WNPS,RNPS);

Parameters

Table 42-9 ROWID_TO_ABSOLUTE_FNO Function Parameters

row_id

schema_name

object_name

Example

DECLARE
     
abs_fno        INTEGER;
rowid_val      CHAR(18);
object_name    VARCHAR2(20) := 'EMP';

     BEGIN
     
SELECT ROWID INTO rowid_val 
FROM emp
WHERE empno = 9999;
 abs_fno := dbms_rowid.rowid_to_absolute_fno(
 rowid_val, 'SCOTT', object_name);

       






Note:



For partitioned objects, the name must be a table name, not a partition or a sub/partition name.  









  

ROWID_TO_EXTENDED function

This function translates a restricted ROWID that addresses a row in a schema and table that you specify to the extended ROWID format. Later, it may be removed from this package into a different place.

Syntax

DBMS_ROWID.ROWID_TO_EXTENDED (
   old_rowid       IN ROWID,
   schema_name     IN VARCHAR2,   
   object_name     IN VARCHAR2,
   conversion_type IN INTEGER)
  RETURN ROWID;

Pragmas

pragma RESTRICT_REFERENCES(rowid_to_extended,WNDS,WNPS,RNPS);

Parameters

Table 42-10 ROWID_TO_EXTENDED Function Parameters

old_rowid

schema_name

object_name

conversion_type

Returns

ROWID_TO_EXTENDED returns the ROWID in the extended character format. If the input ROWID is NULL, then the function returns NULL. If a zero-valued ROWID is supplied (00000000.0000.0000), then a zero-valued restricted ROWID is returned.

Example

Assume that there is a table called RIDS in the schema SCOTT, and that the table contains a column ROWID_COL that holds ROWIDs (restricted), and a column TABLE_COL that point to other tables in the SCOTT schema. You can convert the ROWIDs to extended format with the statement:

UPDATE SCOTT.RIDS
     
SET rowid_col =
dbms_rowid.rowid_to_extended (
   rowid_col, 'SCOTT", TABLE_COL, 0);

         

Usage Notes

If the schema and object names are provided as IN parameters, then this function verifies SELECT authority on the table named, and converts the restricted ROWID provided to an extended ROWID, using the data object number of the table. That ROWID_TO_EXTENDED returns a value, however, does not guarantee that the converted ROWID actually references a valid row in the table, either at the time that the function is called, or when the extended ROWID is actually used.

If the schema and object name are not provided (are passed as NULL), then this function attempts to fetch the page specified by the restricted ROWID provided. It treats the file number stored in this ROWID as the absolute file number. This can cause problems if the file has been dropped, and its number has been reused prior to the migration. If the fetched page belongs to a valid table, then the data object number of this table is used in converting to an extended ROWID value. This is very inefficient, and Oracle recommends doing this only as a last resort, when the target table is not known. The user must still know the correct table name at the time of using the converted value.

If an extended ROWID value is supplied, the data object number in the input extended ROWID is verified against the data object number computed from the table name parameter. If the two numbers do not match, the INVALID_ROWID exception is raised. If they do match, the input ROWID is returned.

ROWID_TO_RESTRICTED function

This function converts an extended ROWID into restricted ROWID format.

Syntax

DBMS_ROWID.ROWID_TO_RESTRICTED (
   old_rowid       IN ROWID,
   conversion_type IN INTEGER)
  RETURN ROWID;

Pragmas

pragma RESTRICT_REFERENCES(rowid_to_restricted,WNDS,RNDS,WNPS,RNPS);

Parameters

Table 42-11 ROWID_TO_RESTRICTED Function Parameters

old_rowid

conversion_type

ROWID_VERIFY function

This function verifies the ROWID. It returns 0 if the input restricted ROWID can be converted to extended format, given the input schema name and table name, and it returns 1 if the conversion is not possible.

Syntax

DBMS_ROWID.ROWID_VERIFY (
   rowid_in        IN ROWID,
   schema_name     IN VARCHAR2,
   object_name     IN VARCHAR2,
   conversion_type IN INTEGER
  RETURN NUMBER;

Pragmas

pragma RESTRICT_REFERENCES(rowid_verify,WNDS,WNPS,RNPS);

Parameters

Table 42-12 ROWID_VERIFY Function Parameters

rowid_in

schema_name

object_name

conversion_type

Example

Considering the schema in the example for the ROWID_TO_EXTENDED function, you can use the following statement to find bad ROWIDs prior to conversion. This enables you to fix them beforehand.

SELECT ROWID, rowid_col 
     
FROM SCOTT.RIDS
WHERE dbms_rowid.rowid_verify(rowid_col, NULL, NULL, 0) =1;

       





See Also:



Chapter  59, "UTL_RAW", Chapter  60, "UTL_REF"