7 Objec t Types

The Expression Filter feature is supplied with a set of predefined types and public synonyms for these types. Most of these types are used for configuring index parameters with the Expression Filter procedural APIs. The EXF$TABLE_ALIAS type is used to support expressions defined on one or more database tables.


All the values and names passed to the types
 defined in this chapter are not case sensitive. To preserve the case, you use double quotation marks around the values.

 
<
font face="arial, helvetica, sans-serif" color="#330099">EXF$ATTRIBUTE

The EXF$ATTRIBUTE type is used to handle stored and indexed attributes for the Expression Filter indexes.

Attributes

Name	Datatype	Description
`attr_name`	`VARCHAR2(350)`	The arithmetic expression that constitutes the st ored or indexed attribute.
`attr_oper`	`EXF$INDEXOPER`	The list of common operators in the predicates with the attribute. Default value: `EXF$INDEXOPER('all')`
`attr_indexed`	`VARCHAR2(5)`	`TRUE` if the attribute is indexed, else `FALSE.` Default value: `FALSE`.

Usage Notes

The EXF$ATTRIBUTE type is used to specify the stored and indexed attributes for an Expression Filter index using th e DBMS_EXPFIL.DEFAULT_INDEX_PARAMETERS procedure. When values for attr_oper and attr_indexed fields are omi tted during EXF$ATTRIBUTE instantiation, it is considered a stored attribute with a default value for common operators ( EXF$INDEXOPER('all')).

Examples

A stored attribute with no preference on the list of common operators is represented as follows:

exf$attribute (attr_name => 'HorsePower(Model, Year)')

An indexed attribute is represented as follows:

exf$attribute (attr_name => 'HorsePower(Model, Year)', 
               a
ttr_indexed => 'TRUE')

An indexed attribute with a list of common operators is represented as follows:

exf$attribute (attr_name => 'HorsePower(Model, Year)', 
               attr_oper => exf$indexoper('=','<','&g
t;','>=','<='), 
               attr_indexed => 'TRUE')

EXF$ATTRIBUTE_LIST

The EXF$ATTRIBUTE _LIST type is defined as follows:

CREATE or    REPLACE TYPE exf$attribute_list as VARRAY(490) of
 exf$attribute;

Attributes

None.

Usage Notes

The EXF$ATTRIBUTE_LIST type is used to specify a list of stored and indexed attributes while configuring the index parameters. (Also see the "DEFAULT_INDEX_PARAMETER S Procedure" in Chapter 8 for more information.)

Examples

A list of stored and indexed at tributes can be represented as follows:

exf$attribute_list (
       exf$attribute (attr_name => 'Mod
el',            
                      attr_oper => exf$indexoper('='),
                      attr_indexed => 'TRUE'),

       exf$attribute (attr_name => 'Price', 
                      attr_oper => exf$indexoper('all'), 
                      a
ttr_indexed => 'TRUE'), 
       exf$attribute (attr_name => 'HorsePower(Model, Year)', 
                      attr_oper => e
xf$indexoper('=','<','>','>=','<='), 
                      attr_indexed => 'FALSE')         
    )

EXF$INDEXOPER

The EXF$INDEXOPER type is used to specify the list of commo n operators in predicates with a stored or an indexed attribute.

The EXF$INDEXOPER type is defined as follows:

CREATE or REPLACE TYPE exfsys.exf$indexoper as VARRAY(20) of VARCHAR2(15);

The values for the EXF$INDEXOPER array are expected to be from the list in the following table:

Value	Predicate Description
=	Equality predicates
>	Greater than predicates
<	Less than predicates
>=	Greater than or equal to predi cates
<=	Less than or equal to predicates
!= or <> or ^=	Not equal to predicates
`IS NULL`	IS NULL predicates
`IS NOT NUL L`	`IS NOT NULL` predicates
`ALL`	All the operators listed in this table starting with the equality predicate through the `IS NOT NULL` predicate
`NVL`	Pred icates with `NVL` (equality) operator
`LIKE`	Predicates with `LIKE` operator
`BETWEEN`	`BETWEEN` predicates

Attributes

None.

Usage Notes

A value of ALL for one of the EXF$INDEXOPER items implies that all the simple operators (=,> ,<,>=,<=,!=, IS NULL, IS NOT NULL) are common in the predicates with an attribute. This value can be used along with one or more complex operators (NVL, LIKE and BETWEEN).

A predicate w ith a BETWEEN operator is treated as two predicates with binary operators, one with '>=' operator and another with '& lt;=' operator. By default, only one of these operators is indexed, and the other operator is evaluated by value substitution. Howeve r, if predicates with the BETWEEN operator are common for an attribute (stored or indexed), both the binary operators re sulting from the BETWEEN operator can be indexed by specifying BETWEEN in the EXF$INDEXOPER VARRAY. However, because this uses additional space in the predicate table, this operator should be used only when majority of predicat es with an attribute use the BETWEEN operator.
When the LIKE operator is chosen as one of the common operators for an attribute, LIKE predicates on that attributes are indexed. Indexing a LIKE operator is be neficial only if the VARCHAR2 constant on the right-hand side of the predicate does not lead with a wild-card character. For example, indexing a LIKE operator will filter the following predicates efficiently: c ompany LIKE 'General%' company LIKE 'Proctor%' But, the following predicates are evaluated as sparse predicates in the la st stage: company LIKE '%Electric' company LIKE "%Gamble' Examples An attribute with a list of c ommon operators is represented as follows: exf$attribute (attr_name => 'HorsePower(Model, Year)', attr_oper => exf$indexoper('=','<','>','>=','<=', 'between'), attr_indexed => 'TRUE')

Datatype	Description
`table_name`	`VARCHAR2(70)`	Name of the table with a possible schema ex tension.

EXF$TABLE_ALIAS A table alias is a special form of elementary attribute that can be included in the attrib ute set. These attributes are used to manage expressions defined on one or more database tables. Attributes < th align="left" valign="bottom" id="r1c1-t4">Name Datatype Description table_name VARCHAR2(70) Name of the table with a possible schema ex tension. Usage Notes
The concept of a table alias attribute is captured in the Expression Filter dictionary and the corresponding attribute in the attribute set's object type is created with a VARCHAR2 datatype. (Also see Appendix A and "ADD_ELEMENTAR Y_ATTRIBUTE Procedure" in Chapter 8.)

Examples

For a set of expressions defined on databa se tables, the corresponding table alias attributes are configured as follows:

BEGIN DBMS_EXPFIL.ADD_ ELEMENTARY_ATTRIBUTE ( attr_set => 'HRAttrSet', attr_name => 'EM P', tab_alias => exf$table_alias('SCOTT.EMP')); DBMS_EXPFIL.ADD_ELEMENTARY_ATTRIBUTE ( attr_set => 'HRAttrSet', attr_name => 'DEPT', tab_alias => exf$table_alias('DEPT')); END; /

The Expression column using the previous attribute set can store expr essions of form EMP.JOB = 'Clerk' and EMP.NAME = 'Joe', where JOB and NAME are the names of th e columns in the SCOTT.EMP table.

EXF$XPATH_TAG

The EXF$XPATH_TAG type is used to con figure an XML element or an XML attribute for indexing a set of XPath predicates.

Attributes

Name Datatype Description

tag_name VARCHAR2(70) Name of the XML element or attribute. The name for an XML attrib ute is formatted as: <ElementName>@<AttributeName>.

tag_indexed

VARCHAR2(5)

TRUE if XML tag is indexed; otherwise FALSE.

Default:

TRUE if the tag is a positional filter.

FALSE if the tag is a value filter.

tag_type VARCHAR2(30) Datatype for the value in the case of value filte r. NULL for positional filters.

Usage Notes

EXF$XPATH_TAG type is used to configure an XML element or an attribute as a positional or a value filter for an Expression Fil ter index (see Chapter 3). An instance of the EXF$XPATH_TAG type with N ULL value for tag_type configures the XML tag as a positional filter. In the current release, the only other poss ible values for the tag_type attribute are strings (CHAR or VARCHAR) and such tags are configu red as value filters. By default, all positional filters are indexed and the value filters are not indexed. This behavior can be over ridden by setting a TRUE or FALSE value for the tag_indexed attribute accordingly.

Examples

< p>An XML element can be configured as a positional filter and be indexed using the following instance of the

EXF$XPATH_TAG type.
exf$xpath_tag(tag_name    => 'stereo',       --- XML element
              tag_indexed =>
; 'TRUE',         --- indexed predicate group
              tag_type    => null)           --- positional filter


An XML
 attribute can be configured as a value filter and be indexed using the following type instance.
exf$xp
ath_tag(tag_name    => 'stereo@make',  --- XML attribute
              tag_indexed => 'TRUE',         --- indexed predicate gro
up
              tag_type    => 'VARCHAR(15)')  --- value filter




 
EXF$XPATH_TAGS
A type used to specify a
 list of XML tags while configuring the Expression Filter index parameters. This type is defined as follows:
CREATE or REPLACE TYPE exf$xpath_tags as VARRAY(490) of exf$xpath_tag;



Attributes
None.
 
Usage Notes
EXF$XPATH_
TAGS type is used to specify a list of XML tags while configuring the Expression Filter index parameters. (See "DEFAULT_XPINDEX_PARAMETERS Procedure" in Chapter 8.)
 
Examples
A list of
 XML tags configured as positional and value filters can be represented as follows:
exf$xpath_tags(
        exf$xpath_tag(tag_name    => 'stereo@make',  --- XML attribute
                         tag_indexed => 'TRUE',
                 tag_type    => 'VARCHAR(15)'), --- value filter
           exf$xpath_tag(tag_name    => 'stereo',       --- XM
L element
                         tag_indexed => 'FALSE',
                         tag_type    => null),          --- position
al filter
           exf$xpath_tag(tag_name    => 'memory',       --- XML element
                         tag_indexed => 'TRUE
',
                         tag_type    => 'VARCHAR(10)')  --- value filter
          )













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7 Objec t Types

< font face="arial, helvetica, sans-serif" color="#330099">EXF$ATTRIBUTE

EXF$ATTRIBUTE_LIST

EXF$INDEXOPER

EXF$TABLE_ALIAS

EXF$XPATH_TAG

EXF$XPATH_TAGS