25 Accessing the Repository using RESOURCE_VIEW and PATH_VIEW

This chapter describes the predefined public views, RESOURCE_VIEW and PATH_VIEW, that provide access to Oracle XML DB repository data. It discusses Oracle SQL functions under_path and equals_path that query resources based on their path names and path and depth that return resource path names and depths, respectively.

This chapter contains these topics:

Overview of Oracle XML DB RESOURCE_VIEW and PATH_VIEW
RESOURCE_VIEW and PATH_VIEW SQL Functions
Using RESOURCE_VIEW and PATH_VIEW SQL Functions
Working with Multiple Oracle XML DB Resources
Performance Tuning of Oracle XML DB Repository Operations
Searching for Resources using Oracle Text

See Also:

Oracle Database Reference for more information about view PATH_VIEW
Oracle Database Reference for more information about view RESOURCE_VIEW

Overview of Oracle XML DB RESOURCE_VIEW and PATH_VIEW

Figure 25-1 shows how Oracle XML DB RESOURCE_VIEW and PATH_VIEW provide a mechanism for using SQL to access data stored in Oracle XML DB Repository. Data stored in the repository using protocols such as FTP and WebDAV, or using application program interfaces (APIs), can be accessed in SQL using RESOURCE_VIEW values and PATH_VIEW values.

RESOURCE_VIEW consists of a resource, itself an XMLType, that contains the name of the resource that can be queried, its ACLs, and its properties, static or extensible.

If the content comprising the resource is XML, stored somewhere in an XMLType table or view, then the RESOURCE_VIEW points to the XMLType row that stores the content.
If the content is not XML, then the RESOURCE_VIEW stores it as a LOB.

Parent-child relationships between folders (necessary to construct the hierarchy) are maintained and traversed efficiently using the hierarchical repository index. Text indexes are available to search the properties of a resource, and internal B-tree indexes over Names and ACLs speed up access to these attributes of the Resource XMLType.

RESOURCE_VIEW and PATH_VIEW, along with PL/SQL package DBMS_XDB, provide all query-based access to Oracle XML DB and DML functionality that is available through the API.

The base table for RESOURCE_VIEW is XDB.XDB$RESOURCE. Access this table only through RESOURCE_VIEW or the DBMS_XDB API.

See Also:

Chapter 3, "Using Oracle XML DB"

Figure 25-1 Accessing Repository Resources using RESOURCE_VIEW and PATH_VIEW

Description of "Figure 25-1 Accessing Repository Resources using RESOURCE_VIEW and PATH_VIEW"

Note:

Neither RESOURCE_VIEW nor PATH_VIEW contains the root folder (/) resource. All other repository resources are included.

RESOURCE_VIEW Definition and Structure

The RESOURCE_VIEW contains one row for each resource in Oracle XML DB Repository (except for the root folder resource). Table 25-1 describes its structure.

Table 25-1 Structure of RESOURCE_VIEW

Column	Data Type	Description
`RES`	`XMLType`	A resource in the repository (except for the root folder resource)
`ANY_PATH`	`VARCHAR2`	An (absolute) path to the resource
`RESID`	`RAW`	Resource OID, which is a unique handle to the resource

PATH_VIEW Definition and Structure

The PATH_VIEW contains one row for each unique path to access a resource in Oracle XML DB Repository (except for the root folder resource). Each resource may have multiple paths, also called links. Table 25-2 describes its structure.

Table 25-2 Structure of PATH_VIEW

Column	Data Type	Description
`PATH`	`VARCHAR2`	An (absolute) path to repository resource `RES`
`RES`	`XMLType`	The resource referred to by column `PATH`
`LINK`	`XMLType`	Link property
`RESID`	`RAW`	Resource OID

Figure 25-2 illustrates the structure of RESOURCE_VIEW and PATH_VIEW.

The path in the RESOURCE_VIEW is an arbitrary one and one of the accessible paths that can be used to access that resource. Oracle SQL function under_path lets applications search for resources that are contained (recursively) within a particular folder, get the resource depth, and so on. Each row in the PATH_VIEW and RESOURCE_VIEW columns is of XMLType. DML on repository views can be used to insert, rename, delete, and update resource properties and contents. Programmatic APIs must be used for some operations, such as creating links to existing resources.

Paths in the ANY_PATH column of the RESOURCE_VIEW and the PATH column in the PATH_VIEW are absolute paths: they start at the root.

Note:

Test resource paths for equality using Oracle SQL function equals_path: equals_path('/my/path') = 1. Do not test ANY_PATH for equality against an absolute path: ANY_PATH = '/my/path'.

Paths returned by the path function are relative paths under the path name specified by function under_path. For example, if there are two resources referenced by path names /a/b/c and /a/d, respectively, then a path expression that retrieves paths under folder /a returns relative paths b/c and d.

When there are multiple hard links to the same resource, only paths under the path name specified by function under_path are returned. If /a/b/c, /a/b/d, and /a/e are all links to the same resource, then a query on PATH_VIEW that retrieves all of the paths under /a/b returns only /a/b/c and /a/b/d, not /a/e.

Figure 25-2 RESOURCE_VIEW and PATH_VIEW Structure

Description of "Figure 25-2 RESOURCE_VIEW and PATH_VIEW Structure"

Understanding the Difference Between RESOURCE_VIEW and PATH_VIEW

Views RESOURCE_VIEW and PATH_VIEW differ as follows:

PATH_VIEW displays all the path names to a particular resource. RESOURCE_VIEW displays one of the possible path names to the resource
PATH_VIEW also displays the properties of the link

Figure 25-3 illustrates this difference between RESOURCE_VIEW and PATH_VIEW.

Because many Internet applications only need one URL to access a resource, RESOURCE_VIEW is widely applicable.

PATH_VIEW contains the link properties as well as resource properties, whereas the RESOURCE_VIEW only contains resource properties.

Whenever possible, use RESOURCE_VIEW, not PATH_VIEW, for better performance. Because it handles the information for multiple paths, PATH_VIEW access can be slower. If you use RESOURCE_VIEW, then the database can determine that only one path is needed, and the index can do less work to determine all the possible paths.

Note:

When using the RESOURCE_VIEW, if you specify a path with functions under_path or equals_path, then they find the resource regardless of whether or not that path is the arbitrary one chosen to normally appear with that resource using RESOURCE_VIEW.

Figure 25-3 RESOURCE_VIEW and PATH_VIEW Explained

Description of "Figure 25-3 RESOURCE_VIEW and PATH_VIEW Explained"

Operations You Can Perform using UNDER_PATH and EQUALS_PATH

You can perform the following operations using Oracle SQL functions under_path and equals_path:

Given a path name:
- Get a resource or its OID
- List the directory given by the path name
- Create a resource
- Delete a resource
- Update a resource
Given a condition that uses under_path or other SQL functions:
- Update resources
- Delete resources
- Get resources or their OID

See the "Using RESOURCE_VIEW and PATH_VIEW SQL Functions" and equals_path.

RESOURCE_VIEW and PATH_VIEW SQL Functions

This section describes Oracle SQL functions that are applicable to RESOURCE_VIEW and PATH_VIEW.

UNDER_PATH SQL Function

Oracle SQL function under_path uses the hierarchical index of Oracle XML DB Repository to return the paths to all hard links under a particular path. This index is designed to speed access when traversing a path (the most common usage).

If the other parts of the query predicate are very selective, however, then a functional implementation of under_path can be chosen that walks back up the repository. This can be more efficient, because fewer links must be traversed. Figure 25-4 shows the under_path syntax.

Figure 25-4 UNDER_PATH Syntax

Description of "Figure 25-4 UNDER_PATH Syntax"

Table 25-3 details the signature of Oracle SQL function under_path.

Table 25-3 UNDER_PATH SQL Function Signature

Syntax	Description
under_path(resource_column, pathname);	Determines whether a resource is under a specified path. Parameters: `resource_column` –The column name or column alias of the `RESOURCE` column in the `PATH_VIEW` or `RESOURCE_VIEW.` `pathname` – The path name to resolve.
under_path(resource_column, depth, pathname);	Determines whether a resource is under a specified path, with a depth argument to restrict the number of levels to search. Parameters: `resource_column` – The column name or column alias of the `RESOURCE` column in the `PATH_VIEW` or `RESOURCE_VIEW.` `depth` – The maximum depth to search. A nonnegative integer. `pathname` – The path name to resolve.
under_path(resource_column, pathname, correlation);	Determines if a resource is under a specified path, with a correlation argument for related SQL functions. Parameters: `resource_column` – The column name or column alias of the `RESOURCE` column in the `PATH_VIEW` or `RESOURCE_VIEW.` `pathname` – The path name to resolve. `correlation` – An integer that can be used to correlate `under_path` with related SQL functions (`path` and `depth`).
under_path(resource_column, depth, pathname, correlation);	Determines if a resource is under a specified path with a depth argument to restrict the number of levels to search, and with a correlation argument for related SQL functions. Parameters: `resource_column` – The column name or column alias of the `RESOURCE` column in the `PATH_VIEW` or `RESOURCE_VIEW`. `depth` – The maximum depth to search. A nonnegative integer. `pathname` – The path name to resolve. `correlation` – An integer that can be used to correlate `under_path` with related SQL functions (`path` and `depth`). Note that only one of the accessible paths to the resource must be under the path argument for a resource to be returned.

Note:

Function under_path does not follow weak links, because such traversal could lead to cycles. A weak-link argument to under_path is resolved correctly, but weak links are not followed when traversing resources under that path.

EQUALS_PATH SQL Function

Oracle SQL function equals_path is used to find the resource with the specified path name. It is functionally equivalent to under_path with a depth restriction of zero.

equals_path(resource_column, pathname);

where:

resource_column is the column name or column alias of the RESOURCE column in PATH_VIEW or RESOURCE_VIEW.
pathname is the (absolute) path name to resolve. This can contain components that are hard or weak resource links.

Figure 25-5 illustrates the complete equals_path syntax.

Figure 25-5 EQUALS_PATH Syntax

Description of "Figure 25-5 EQUALS_PATH Syntax"

Note:

Test resource paths for equality using Oracle SQL function equals_path: equals_path('/my/path') = 1. Do not test ANY_PATH for equality against an absolute path: ANY_PATH = '/my/path'.
Use bind variables, instead of hard-coded strings, with equals_path.

PATH SQL Function

Oracle SQL function path returns the relative path name of the resource under the specified pathname argument. Note that the path column in the RESOURCE_VIEW always contains the absolute path of the resource. The path syntax is:

path(correlation);

where:

correlation is an integer that can be used to correlate under_path with related SQL functions (path and depth).

Note:
If a path is not under the specified pathname argument, a NULL value is returned as the output of the current path.

Figure 25-6 illustrates the path syntax.

Figure 25-6 PATH Syntax

Description of "Figure 25-6 PATH Syntax"

DEPTH SQL Function

Oracle SQL function depth returns the folder depth of the resource under the specified starting path.

depth(correlation);

where:

correlation is an integer that can be used to correlate under_path with related SQL functions (path and depth).

Using RESOURCE_VIEW and PATH_VIEW SQL Functions

The following RESOURCE_VIEW and PATH_VIEW examples use Oracle SQL functions under_path, equals_path, path, and depth.

Accessing Repository Data Paths, Resources and Links: Examples

The following examples illustrate how you can access paths, resources, and link properties in Oracle XML DB Repository. The first few examples use resources specified by the following paths:

/a/b/c
/a/b/c/d
/a/e/c
/a/e/c/d

Example 25-1 uses Oracle SQL function path to retrieve the relative paths under path /a/b.

Example 25-1 Determining Paths Under a Path: Relative

SELECT path(1) FROM RESOURCE_VIEW WHERE under_path(RES, '/a/b', 1) = 1;

PATH(1)
-------
c
c/d

2 rows selected.

Example 25-2 uses ANY_PATH to retrieve the absolute paths under path /a/b.

Example 25-2 Determining Paths Under a Path: Absolute

SELECT ANY_PATH FROM RESOURCE_VIEW WHERE under_path(RES, '/a/b') = 1;

ANY_PATH
--------
/a/b/c
/a/b/c/d

2 rows selected.

Example 25-3 is the same as Example 25-2, except that the test is not-equals (!=) instead of equals (=). The query in Example 25-3 finds all paths in the repository that are not under path /a/b.

Example 25-3 Determining Paths Not Under a Path

SELECT ANY_PATH FROM RESOURCE_VIEW WHERE under_path(RES, '/a/b') != 1

ANY_PATH
--------
/a
/a/b
/a/e
/a/e/c
/a/e/c/d
/home
/home/OE
/home/OE/PurchaseOrders
/home/OE/PurchaseOrders/2002
/home/OE/PurchaseOrders/2002/Apr
/home/OE/PurchaseOrders/2002/Apr/AMCEWEN-20021009123336171PDT.xml
/home/OE/PurchaseOrders/2002/Apr/AMCEWEN-20021009123336271PDT.xml
/home/OE/PurchaseOrders/2002/Apr/EABEL-20021009123336251PDT.xml
. . .
/public
/sys
/sys/acls
/sys/acls/all_all_acl.xml
/sys/acls/all_owner_acl.xml
/sys/acls/bootstrap_acl.xml
/sys/acls/ro_all_acl.xml
/sys/apps
/sys/apps/plsql
/sys/apps/plsql/xs
/sys/apps/plsql/xs/netaclrc.xml
/sys/apps/plsql/xs/netaclsc.xml
/sys/databaseSummary.xml
/sys/log
/sys/schemas
/sys/schemas/OE
/sys/schemas/OE/localhost:8080
. . .

326 rows selected.

Example 25-4 Determining Paths using Multiple Correlations

SELECT ANY_PATH, path(1), path(2) 
  FROM RESOURCE_VIEW
  WHERE under_path(RES, '/a/b', 1) = 1 OR under_path(RES, '/a/e', 2) = 1;

ANY_PATH   PATH(1)  PATH(2)
---------- -------- --------
/a/b/c     c
/a/b/c/d   c/d
/a/e/c              c
/a/e/c/d            c/d
 
4 rows selected.

Example 25-5 Relative Path Names for Three Levels of Resources

SELECT path(1) FROM RESOURCE_VIEW WHERE under_path(RES, 3, '/sys', 1) = 1;

This produces a result similar to the following.

PATH(1)
-------
acls
acls/all_all_acl.xml
acls/all_owner_acl.xml
acls/bootstrap_acl.xml
acls/ro_all_acl.xml
apps
apps/plsql
apps/plsql/xs
databaseSummary.xml
log
schemas
schemas/OE
schemas/OE/localhost:8080
schemas/PUBLIC
schemas/PUBLIC/www.w3.org
schemas/PUBLIC/xmlns.oracle.com
 
93 rows selected.

Example 25-6 Extracting Resource Metadata using UNDER_PATH

SELECT ANY_PATH,
       XMLQuery('declare namespace ns = "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                 $r/ns:Resource' PASSING RES AS "r" RETURNING CONTENT)
  FROM RESOURCE_VIEW WHERE under_path(RES, '/sys') = 1;

This produces a result similar to the following:

ANY_PATH
--------
XMLQUERY('DECLARENAMESPACENS="HTTP://XMLNS.ORACLE.COM/XDB/XDBRESOURCE.XSD";(::)$
--------------------------------------------------------------------------------
/sys/acls
<Resource xmlns="http://xmlns.oracle.com/xdb/XDBResource.xsd">
  <CreationDate>2008-06-25T13:17:45.164662</CreationDate>
  <ModificationDate>2008-06-25T13:17:47.865163</ModificationDate>
  <DisplayName>acls</DisplayName>
  <Language>en-US</Language>
  <CharacterSet>UTF-8</CharacterSet>
  <ContentType>application/octet-stream</ContentType>
  <RefCount>1</RefCount>
</Resource>
 
/sys/acls/all_all_acl.xml
<Resource xmlns="http://xmlns.oracle.com/xdb/XDBResource.xsd">
  <CreationDate>2008-06-25T13:17:47.759806</CreationDate>
  <ModificationDate>2008-06-25T13:17:47.759806</ModificationDate>
  <DisplayName>all_all_acl.xml</DisplayName>
  <Language>en-US</Language>
  <CharacterSet>UTF-8</CharacterSet>
  <ContentType>text/xml</ContentType>
  <RefCount>1</RefCount>
</Resource>
. . .
41 rows selected.

Example 25-7 Using Functions PATH and DEPTH with PATH_VIEW

SELECT path(1) path, depth(1) depth FROM PATH_VIEW 
  WHERE under_path(RES, 3, '/sys', 1) = 1;

This produces a result similar to the following:

PATH                                      DEPTH
----                                      -----
acls                                      1
acls/all_all_acl.xml                      2
acls/all_owner_acl.xml                    2
acls/bootstrap_acl.xml                    2
acls/ro_all_acl.xml                       2
apps                                      1
apps/plsql                                2
apps/plsql/xs                             3
databaseSummary.xml                       1
log                                       1
schemas                                   1
schemas/OE                                2
schemas/OE/localhost:8080                 3
schemas/PUBLIC                            2
schemas/PUBLIC/www.w3.org                 3
schemas/PUBLIC/xmlns.oracle.com           3
. . .

Example 25-8 Extracting Link and Resource Information from PATH_VIEW

SELECT PATH, 
       XMLCast(XMLQuery(
                 'declare namespace ns =
                           "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                  $l/ns:LINK/ns:Name' PASSING LINK AS "l" RETURNING CONTENT)
               AS VARCHAR2(256)),
       XMLCast(XMLQuery(
                 'declare namespace ns =
                           "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                  $l/ns:LINK/ns:ParentName' PASSING LINK AS "l" RETURNING CONTENT)
               AS VARCHAR2(256)),
       XMLCast(XMLQuery(
                 'declare namespace ns =
                           "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                  $l/ns:LINK/ns:ChildName' PASSING LINK AS "l" RETURNING CONTENT)
               AS VARCHAR2(256)),
       XMLCast(XMLQuery(
                 'declare namespace ns =
                           "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                  $r/ns:Resource/ns:DisplayName' 
                    PASSING RES AS "r" RETURNING CONTENT)
               AS VARCHAR2(128))
  FROM PATH_VIEW WHERE PATH LIKE '/sys%';

This produces a result similar to the following:

/sys/schemas/PUBLIC/www.w3.org/1999/xlink.xsd
xlink.xsd
 
/sys/schemas/PUBLIC/www.w3.org/1999/xlink
xlink
 
/sys/schemas/PUBLIC/www.w3.org/1999/csx.xlink.xsd
csx.xlink.xsd

. . .

118 rows selected.

Example 25-9 All Repository Paths to a Certain Depth Under a Path

SELECT path(1) FROM PATH_VIEW WHERE under_path(RES, 3, '/sys', 1) > 0 ;

This produces a result similar to the following:

PATH(1)
-------
acls
acls/all_all_acl.xml
acls/all_owner_acl.xml
acls/bootstrap_acl.xml
acls/ro_all_acl.xml
apps
apps/plsql
apps/plsql/xs
databaseSummary.xml
log
principals
principals/groups
principals/users
schemas
schemas/PUBLIC
schemas/PUBLIC/www.opengis.net
schemas/PUBLIC/www.w3.org
schemas/PUBLIC/xmlns.oracle.com
workspaces
. . .
 
43 rows selected.

Example 25-10 Locating a Repository Path using EQUALS_PATH

SELECT ANY_PATH FROM RESOURCE_VIEW WHERE equals_path(RES, '/sys') > 0;

ANY_PATH
--------
/sys
 
1 row selected.

Example 25-11 Retrieve RESID of a Given Resource

SELECT RESID FROM RESOURCE_VIEW
  WHERE XMLCast(XMLQuery(
                  'declare namespace ns = 
                     "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                   $r/ns:Resource/ns:DisplayName'
                  PASSING RES AS "r" RETURNING CONTENT)
                AS VARCHAR2(128))
        = 'example';

This produces a result similar to the following:

RESID
--------------------------------
F301A10152470252E030578CB00B432B
 
1 row selected.

Example 25-12 Obtaining the Path Name of a Resource from its RESID

DECLARE
  resid_example RAW(16);
  path          VARCHAR2(4000);
BEGIN
  SELECT RESID INTO resid_example FROM RESOURCE_VIEW
    WHERE XMLCast(XMLQuery(
                    'declare namespace ns =
                       "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                     $r/ns:Resource/ns:DisplayName'
                    PASSING RES AS "r" RETURNING CONTENT)
                  AS VARCHAR2(128))
 
          = 'example';
  SELECT ANY_PATH INTO path FROM RESOURCE_VIEW WHERE RESID = resid_example;
  DBMS_OUTPUT.put_line('The path is: ' || path);
END;
/
The path is: /public/example
 
PL/SQL procedure successfully completed.

Example 25-13 Folders Under a Given Path

SELECT ANY_PATH FROM RESOURCE_VIEW
  WHERE under_path(RES, 1, '/sys') = 1
    AND XMLExists('declare namespace ns = 
                     "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                   $r/ns:Resource[@Container = xs:boolean("true")]'
                  PASSING RES AS "r");

This produces a result like the following:

ANY_PATH
--------
/sys/acls
/sys/apps
/sys/log
/sys/schemas
 
4 rows selected.

Example 25-14 Joining RESOURCE_VIEW with an XMLType Table

SELECT ANY_PATH, XMLQuery('$p/PurchaseOrder/LineItems'
                          PASSING po.OBJECT_VALUE AS "p" RETURNING CONTENT)
  FROM purchaseorder po, RESOURCE_VIEW rv
  WHERE ref(po)
        = XMLCast(XMLQuery('declare default element namespace
                            "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                            fn:data(/Resource/XMLRef)'
                           PASSING rv.RES RETURNING CONTENT)
                  AS REF XMLType)
    AND ROWNUM < 2;
 
ANY_PATH
--------------------------------------------------------------------------------
XMLQUERY('$P/PURCHASEORDER/LINEITEMS'PASSINGPO.OBJECT_VALUEAS"P"RETURNINGCONTENT
--------------------------------------------------------------------------------
/home/OE/PurchaseOrders/2002/Apr/AMCEWEN-20021009123336171PDT.xml
<LineItems>
  <LineItem ItemNumber="1">
    <Description>Salesman</Description>
    <Part Id="37429158920" UnitPrice="39.95" Quantity="2"/>
  </LineItem>
  <LineItem ItemNumber="2">
    <Description>Big Deal on Madonna Street</Description>
    <Part Id="37429155424" UnitPrice="29.95" Quantity="1"/>
  </LineItem>
  <LineItem ItemNumber="3">
    <Description>Hearts and Minds</Description>
    <Part Id="37429166321" UnitPrice="39.95" Quantity="1"/>
  </LineItem>

. . .

  <LineItem ItemNumber="23">
    <Description>Great Expectations</Description>
    <Part Id="37429128022" UnitPrice="39.95" Quantity="4"/>
  </LineItem>
</LineItems>
 
1 row selected.

Deleting Repository Resources: Examples

The examples in this section illustrate how to delete resources and paths.

If you delete only leaf resources, then you can use DELETE FROM RESOURCE_VIEW, as in Example 25-15.

Example 25-15 Deleting Resources

DELETE FROM RESOURCE_VIEW WHERE equals_path(RES, '/public/myfile') = 1';

For multiple links to the same resource, deleting from RESOURCE_VIEW deletes the resource together with all of its links; deleting from PATH_VIEW deletes only the link with the specified path.

Example 25-16 illustrates this.

Example 25-16 Deleting Links to Resources

Suppose that '/home/myfile1' is a link to '/public/myfile':

CALL DBMS_XDB.link('/public/myfile', '/home', 'myfile1');

The following SQL DML statement deletes everything in Oracle XML DB Repository that is found at path /home/myfile1 – both the link and the resource:

DELETE FROM RESOURCE_VIEW WHERE equals_path(RES, '/home/myfile1') = 1;

The following DML statement deletes only the link with path /home/file1:

DELETE FROM PATH_VIEW WHERE equals_path(RES, '/home/file1') = 1;

Deleting Nonempty Folder Resources

The DELETE DML operator is not allowed on a nonempty folder. If you try to delete a nonempty folder, you must first delete its contents and then delete the resulting empty folder. This rule must be applied recursively to any folders contained in the target folder.

However, the order of the paths returned from a WHERE clause is not guaranteed, and the DELETE operator does not allow an ORDER BY clause in its table-expression subclause. This means that you cannot do the following:

DELETE FROM (SELECT 1 FROM RESOURCE_VIEW
               WHERE under_path(RES, '/public', 1) = 1
               ORDER BY depth(1) DESCENDING);

Example 25-17 illustrates how to delete a nonempty folder: folder example is deleted, along with its subfolder example1.

Example 25-17 Deleting a Nonempty Folder

SELECT PATH FROM PATH_VIEW WHERE under_path(RES, '/home/US1') = 1;
 
PATH
--------------------------
/home/US1/example
/home/US1/example/example1
 
2 rows selected.

DECLARE
  CURSOR c1 IS
    SELECT ANY_PATH p FROM RESOURCE_VIEW
      WHERE under_path(RES, '/home/US1', 1) = 1
        AND XMLExists('declare namespace ns =
                         "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                       $r/ns:Resource[ns:Owner="US1"]' PASSING RES AS "r")
      ORDER BY depth(1) DESC;
  del_stmt VARCHAR2(500) :=
    'DELETE FROM RESOURCE_VIEW WHERE equals_path(RES, :1)=1';
BEGIN
  FOR r1 IN c1 LOOP
    EXECUTE IMMEDIATE del_stmt USING r1.p;
  END LOOP;
END;
/
 
PL/SQL procedure successfully completed.
 
SELECT PATH FROM PATH_VIEW WHERE under_path(RES, '/home/US1') = 1;
 
no rows selected

Note:

As always, take care to avoid deadlocks with concurrent transactions when operating on multiple rows.

Updating Repository Resources: Examples

This section illustrates how to update resources and paths.

Example 25-18 changes the resource at path /test/HR/example/paper.

Example 25-18 Updating a Resource

This is the complete resource before the update operation:

SELECT XMLSerialize(DOCUMENT r.RES AS CLOB)
  FROM RESOURCE_VIEW r WHERE equals_path(r.RES, '/test/HR/example/paper') = 1;
 
XMLSERIALIZE(DOCUMENTR.RESASCLOB)
--------------------------------------------------------------------------------
<Resource xmlns="http://xmlns.oracle.com/xdb/XDBResource.xsd" Hidden="false" Inv
alid="false" Container="false" CustomRslv="false" VersionHistory="false" StickyR
ef="true">
  <CreationDate>2005-04-29T16:30:01.588835</CreationDate>
  <ModificationDate>2005-04-29T16:30:01.588835</ModificationDate>
  <DisplayName>paper</DisplayName>
  <Language>en-US</Language>
  <CharacterSet>UTF-8</CharacterSet>
  <ContentType>application/octet-stream</ContentType>
  <RefCount>1</RefCount>
  <ACL>
    <acl description="Public:All privileges to PUBLIC" xmlns="http://xmlns.oracl
e.com/xdb/acl.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:sch
emaLocation="http://xmlns.oracle.com/xdb/acl.xsd                           http:
//xmlns.oracle.com/xdb/acl.xsd">
      <ace>
        <principal>PUBLIC</principal>
        <grant>true</grant>
        <privilege>
          <all/>
        </privilege>
      </ace>
    </acl>
  </ACL>
  <Owner>TESTUSER1</Owner>
  <Creator>TESTUSER1</Creator>
  <LastModifier>TESTUSER1</LastModifier>
  <SchemaElement>http://xmlns.oracle.com/xdb/XDBSchema.xsd#binary</SchemaElement
>
  <Contents>
    <binary>4F7261636C65206F7220554E4958</binary>
  </Contents>
</Resource>
 
1 row selected.

All of the XML elements shown here are resource metadata elements, with the exception of Contents, which contains the resource content.

This UPDATE statement updates (only) the DisplayName metadata element.

UPDATE RESOURCE_VIEW r
  SET r.RES = updateXML(r.RES, '/Resource/DisplayName/text()', 'My New Paper')
    WHERE equals_path(r.RES, '/test/HR/example/paper') = 1;
 
1 row updated.

SELECT XMLSerialize(DOCUMENT r.RES AS CLOB)
  FROM RESOURCE_VIEW r WHERE equals_path(r.RES, '/test/HR/example/paper') = 1;
 
XMLSERIALIZE(DOCUMENTR.RESASCLOB)
--------------------------------------------------------------------------------
<Resource xmlns="http://xmlns.oracle.com/xdb/XDBResource.xsd" Hidden="false" Inv
alid="false" Container="false" CustomRslv="false" VersionHistory="false" StickyR
ef="true">
  <CreationDate>2005-04-29T16:30:01.588835</CreationDate>
  <ModificationDate>2005-04-29T16:30:01.883838</ModificationDate>
  <DisplayName>My New Paper</DisplayName>
  <Language>en-US</Language>

  . . .

  <Contents>
    <binary>4F7261636C65206F7220554E4958</binary>
  </Contents>
</Resource>
 
1 row selected.

See Also:

Chapter 29, "User-Defined Repository Metadata" for additional examples of updating resource metadata

Note that, by default, the DisplayName element content, paper, was the same text as the last location step of the resource path, /test/HR/example/paper. This is only the default value, however. The DisplayName is independent of the resource path, so updating it does not change the path.

Element DisplayName is defined by the WebDAV standard, and it is recognized by WebDAV applications. Applications, such as an FTP client, that are not WebDAV-based do not recognize the DisplayName of a resource. An FTP client lists the resource as paper (using FTP command ls, for example) even after the UPDATE operation.

Example 25-19 changes the path for the resource from /test/HR/example/paper to /test/myexample. It is analogous to using the UNIX or Linux command mv /test/HR/example/paper /test/myexample.

Example 25-19 Updating a Path in the PATH_VIEW

SELECT ANY_PATH FROM RESOURCE_VIEW WHERE under_path(RES, '/test') = 1;
 
ANY_PATH
--------
/test/HR
/test/HR/example
/test/HR/example/paper
 
3 rows selected.

UPDATE PATH_VIEW 
  SET PATH = '/test/myexample' WHERE PATH = '/test/HR/example/paper';

ANY_PATH
--------
/test/HR
/test/HR/example
/test/myexample
 
3 rows selected.

See Also:

Table 21-3, "Accessing Oracle XML DB Repository: API Options" for additional examples that use SQL functions that apply to RESOURCE_VIEW and PATH_VIEW

Working with Multiple Oracle XML DB Resources

The repository operations listed in Table 21-3 typically apply to a single resource at a time. To perform the same operation on multiple Oracle XML DB resources, or to find one or more Oracle XML DB resources that meet a certain set of criteria, use SQL with RESOURCE_VIEW and PATH_VIEW.

For example, you can perform the following operations:

Updating based on attributes – see Example 25-20
Finding resources inside a folder – see Example 25-21
Copying a set of Oracle XML DB resources – see Example 25-22

Example 25-20 Updating Resources Based on Attributes

UPDATE RESOURCE_VIEW
  SET RES = updateXML(RES, '/Resource/DisplayName/text()', 'My New Paper')
    WHERE XMLCast(XMLQuery(
                    'declare namespace ns =
                       "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                     $r/ns:Resource/ns:DisplayName'
                    PASSING RES AS "r" RETURNING CONTENT)
                  AS VARCHAR2(128))
          = 'My Paper';
 
1 row updated.
 
SELECT ANY_PATH FROM RESOURCE_VIEW
  WHERE XMLCast(XMLQuery('declare namespace ns =
                            "http://xmlns.oracle.com/xdb/XDBResource.xsd"; (: :)
                          $r/ns:Resource/ns:DisplayName'
                         PASSING RES AS "r" RETURNING CONTENT)
                AS VARCHAR2(128))
          = 'My New Paper';
 
ANY_PATH
---------------
/test/myexample
 
1 row selected.

Example 25-21 Finding Resources Inside a Folder

SELECT ANY_PATH FROM RESOURCE_VIEW
  WHERE under_path(resource, '/sys/schemas/PUBLIC/xmlns.oracle.com/xdb') = 1;

ANY_PATH
--------------------------------------------------------------
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/XDBFolderListing.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/XDBResource.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/XDBSchema.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/XDBStandard.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/acl.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/dav.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/log
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/log/ftplog.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/log/httplog.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/log/xdblog.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/stats.xsd
/sys/schemas/PUBLIC/xmlns.oracle.com/xdb/xdbconfig.xsd
 
12 rows selected.

The SQL DML statement in Example 25-22 copies all of the resources in folder public to folder newlocation. It is analogous to the UNIX or Linux command cp /public/* /newlocation. Target folder newlocation must exist before the copy.

Example 25-22 Copying Resources

SELECT PATH FROM PATH_VIEW WHERE under_path(RES, '/test') = 1;
 
PATH
-----------------
/test/HR
/test/HR/example
/test/myexample
 
3 rows selected.
 
INSERT INTO PATH_VIEW
  SELECT '/newlocation/' || path(1), RES, LINK, NULL FROM PATH_VIEW
    WHERE under_path(RES, '/test', 1) = 1
    ORDER BY depth(1);
 
3 rows created.
 
SELECT PATH FROM PATH_VIEW WHERE under_path(RES, '/newlocation') = 1;
 
PATH
------------------------
/newlocation/HR
/newlocation/HR/example
/newlocation/myexample
 
3 rows selected.

Performance Tuning of Oracle XML DB Repository Operations

This section includes some guidelines for improving the performance of repository operations such as resource creation and querying.

For optimal performance of queries on repository resources, gather statistics for the optimizer using procedure DBMS_XDB_ADMIN.gatherRepositoryStats after resource creation. To use gatherRepositoryStats, you need role DBA or role XDBADMIN with privilege ANALYZE ANY.

Folders that contain a large number of resources can negatively affect concurrency, particularly when many resources are created or deleted. As a rule of thumb, do not have folders that contain more than 10,000 resources. This empirical limit is based on the database block size and the average filename length.

If you create resources in bulk, perform a COMMIT operation at least every 1,000 resources. Performance can be negatively impacted if you commit very often or you commit less often than every 1,000 resource creations.

When creating a file resource that is an XML Schema-based document for which the XML schema is known, specify the XML schema URL as a parameter to PL/SQL function DBMS_XDB.createResource. This saves preparsing the document to determine the XML schema.

Oracle XML DB uses configuration file xdbconfig.xml for configuring the system and protocol environment. This file includes an element parameter, resource-view-cache-size, that defines the size in dynamic memory of the RESOURCE_VIEW cache. The default value is 1048576.

The performance of some queries on RESOURCE_VIEW and PATH_VIEW can be improved by tuning resource-view-cache-size. In general, the bigger the cache size, the faster the query. The default resource-view-cache-size is appropriate for most cases, but you may want to enlarge your resource-view-cache-size element when querying a sizable RESOURCE_VIEW.

The default limits for the following elements are soft limits. The system automatically adapts when these limits are exceeded.

xdbcore-loadableunit-size – This element indicates the maximum size to which a loadable unit (partition) can grow in Kilobytes. When a partition is read into memory or a partition is built while consuming a new document, the partition is built until it reaches the maximum size. The default value is 16 KB.
xdbcore-xobmem-bound – This element indicates the maximum memory in kilobytes that a document is allowed to occupy. The default value is 1024 KB. Once the document exceeds this number, some loadable units (partitions) are swapped out.

See Also:

Chapter 34, "Administering Oracle XML DB"
Oracle Database PL/SQL Packages and Types Reference for information about PL/SQL function DBMS_XDB.createResource
Oracle Database 2 Day + Security Guide for information about database schema XDB

Searching for Resources using Oracle Text

Table XDB$RESOURCE in database schema XDB stores the metadata and content of repository resources. You can search for resources that contain a specific keyword by using Oracle SQL function contains with RESOURCE_VIEW or PATH_VIEW.

Example 25-23 Find All Resources Containing "Paper"

SELECT PATH FROM PATH_VIEW WHERE contains(RES, 'Paper') > 0;

PATH
-----------------------
/newlocation/myexample
/test/myexample
 
2 rows selected.

Example 25-24 Find All Resources Containing "Paper" that are Under a Specified Path

SELECT ANY_PATH FROM RESOURCE_VIEW
   WHERE contains(RES, 'Paper') > 0 AND under_path(RES, '/test') > 0;

ANY_PATH
----------------
/test/myexample
 
1 row selected.

To evaluate such queries, you must first create a context index on the XDB$RESOURCE table. Depending on the type of documents stored in Oracle XML DB, choose one of the following options for creating your context index:

If Oracle XML DB contains only XML documents, that is, no binary data, then a regular Context Index can be created on the XDB$RESOURCE table. This is the case for Example 25-24.
```
CREATE INDEX xdb$resource_ctx_i ON XDB.XDB$RESOURCE(OBJECT_VALUE)
  INDEXTYPE IS CTXSYS.CONTEXT;
```
See Also:
Chapter 4, "XMLType Operations" and Chapter 12, "Full-Text Search Over XML Data"
If Oracle XML DB contains binary data such as Microsoft Word documents, then a user filter is required to filter such documents prior to indexing. Use package DBMS_XDBT (dbmsxdbt.sql) to create and configure the Context Index.
```
-- Install the package - connected as SYS
@dbmsxdbt
-- Create the preferences
EXEC DBMS_XDBT.createPreferences;
-- Create the index
EXEC DBMS_XDBT.createIndex;
```
See Also:
- Oracle Database PL/SQL Packages and Types Reference, for information about installing and using DBMS_XDBT.
- "APIs for XML"

Package DBMS_XDBT also includes procedures to synchronize and optimize the index. You can use procedure configureAutoSync() to configure automatically sync the index by using job queues.