Mar 26, 2009

Oracle Wokspace 3

To Refresh workspace


But if there are conflicts refreshworkspace will result an error

ORA-20056: conflicts detected for workspace: 'B_focus_9' in table: 'USER.TEST'


The two rows that changed in both the LIVE and the 'B_focus_9' workspace create a conflict. These conflicts can be seen from the view Test_conf. But first go to the 'B_focus_9' workspace. The conflicts are not visible in this view while being in the LIVE workspace.

To Resolve this conflicts

SELECT * FROM test_conf ORDER BY wm_workspace;

dbms_wm.resolveconflicts('B_focus_9','TEST',null/*where clause*/,'PARENT');


SELECT * FROM test_conf ORDER BY wm_workspace;

After resolving this conflict the workspace can be refreshed


Merge Workspace


When B_focus_9 workspace is merged into the LIVE workspace. A merge is the opposite of a refresh : it updates the parent workspace (LIVE) with the changes made to the merged workspace (B_focus_9). Where as refresh operation updates the refreshing workspace.

After MergeWorkspace See Difference


select * from test order by one


select * from test order by one


select * from test order by one

Here parent workspace (LIVE) was updated by merged workspace (B_focus_9) .


Mar 25, 2009

Oracle Workspace 2

The merge operation does not currently work with versioned tables. The optimizer translates the merge into
insert/update statements on the underlying _LT table

To have several versions of data

create table TEST (
one number primary key, -- Without primary key: ORA-20133:
two varchar2(15), three char(2), four clob,
five blob, six date );

insert into test values (1,'Cochin','NO','Kochi is a vibrant city situated on the south-west coast of the Indian peninsula in the breathtakingly scenic and prosperous state of Kerala, hailed as Gods Own Country',null,sysdate);

insert into test values (2,'Kerala','YS','n',null,sysdate);
insert into test values (3,'TVM','NO','n',null,sysdate);
insert into test values (4,'Calicut','NO','n',null,sysdate);
insert into test values (5,'Kannur','YS','n',null,sysdate);


dbms_wm.enableversioning ('test');

dbms_wm.createworkspace ('B_focus_1');
dbms_wm.createworkspace ('B_focus_9' );

dbms_wm.createworkspace ('test' );

select workspace, parent_workspace from user_workspaces;

select * from test order by one;

update test set two='Kasargode',three='NO',four='Top end of Kerala',Six=sysdate where one=2;



select * from test order by one


select * from test order by one

update test set two='Thrissur',three='NO',four='Middle of Kerala',Six=sysdate where one=2;

select * from test order by one


select * from test order by one

Oracle Workspace 1

Workspace Manager PL/SQL APIs

The PL/SQL APIs in the DBMS_WM package can be executed

* Workspace operations: create,refresh,merge,rollback remove,goto,compress,alter
* Savepoints: create, alter, goto
* History: goto date
* Privileges: access, create, delete, rollback and merge workspace
* Access Modes: read, write, management or no access to workspaces
* Locks: exclusive and shared workspace locks to prevent data update conflicts
* Find Differences: compare savepoints and workspaces
* Detect / Resolve Conflicts: Automatically detect and resolve conflicts

When a particular table is versioned primary key index is rebuild version field is added with the current primary key fields inorder to uniquely identify each row version .Each table that is versioned with the workspace manager must have a primary key.No issue if there is a Foreign Key

To get Lock Mode

SELECT dbms_wm.GetLockMode FROM dual;

Some Errors

ORA-20101: child table must be version enabled (This error occur if TEST table is referenced by another table TESTCHILD ;if TESTCHILD is version enabled then only TEST table can be versioned )

(II)ORA-20100: 'USER.TEST' is both parent and child tables of referential integrity constraints

If a field of TEST table is referenced by another field of TEST table itself such tables cannot be version-
enabled ie:( In Scott.EMP table MGR field is referenced by EMPNO field )


(III) Temporary Table cannot be version enabled

ORA-20229:statement 'CREATE INDEX TMP_TEST_PKI$ on TMP_TEST_LT(A)LOGGING PCTFREE 10 INITRANS 2 M' failed during EnableVersioning.Error:
ORA-14451: unsupported feature with temporary table

Referential integrity constraints cannot be added after versioning is enabled. They must be present before version-enabling


SELECT dbms_wm.GetPrivs('LIVE') FROM dual ; //GET Privileges of particular workspace

To Get Lock Mode
SELECT dbms_wm.GetLockMode FROM dual ;

lockmode varchar2(1);
lockMode := sys.lt_ctx_pkg.lock_Mode;

The min & max time that Oracle supports

SELECT DBMS_WM.max_time,DBMS_WM.min_time FROM DUAL; (from 10g onwards)

Mar 19, 2009

Oracle Workspace

With Oracle's Workspace Manager it's possible to have several versions of data. That is, data can be changed, thus making a new version, without affecting application data.For this a new workspace is to be created and the table is to be versioned

Workspace allows multiple transactions to exist within one table in a schema. This allows several departments or functional areas to work against a single schema without interfering with data from other groups. Changes to version-enabled tables are captured as new rows within the workspace. These changes are invisible to other workspaces until they are merged into a parent workspace.

The functionality (Packages, Procedures, Functions) used for the Workspace Manager are found in the wmsys schema.

In a workspace hierarchy consisting of Live->PreProduction->Development workspaces, the Development workspace can see all row changes made in the PreProduction workspace, along with all committed data from non-version-enabled tables belonging to the Live workspace. In addition it can see data from version-enabled tables in Live as they were when the PreProduction workspace was created. Once a workspace is refreshed, all changes can be cascaded down the hierarchy.

Workspace Manager makes only a copy of row it is changed ,which reduce hardware , software and time needed to manage multiple version of data in different schemas .A workspace is a virtual environment not physical storage.The default workspace is called LIVE.

Main concepts used for workspace are Instead of Triggers and Context .

For More On WorkSpace

To get Version

SELECT dbms_wm.getversion FROM dual;

To create Workspace


select workspace, parent_workspace from user_workspaces;

To move to workspace


To enable versoning for a table

dbms_wm.enableversioning (table_name,hist);

1)The length of a table name must not exceed 25 characters. The name is not case sensitive

2) Hist

NONE: No modifications to the table are tracked. (This is the default.)

VIEW_W_OVERWRITE: The with overwrite (W_OVERWRITE) option: A view named _HIST is created to contain history information, but it will show only the most recent modifications to the same version of the table. A history of modifications to the version is not maintained; that is, subsequent changes to a row in the same version overwrite earlier changes. (The CREATETIME column of the _HIST view contains only the time of the most recent update.)

VIEW_WO_OVERWRITE: The without overwrite (WO_OVERWRITE) option: A view named _HIST is created to contain history information, and it will show all modifications to the same version of the table. A history of modifications to the version is maintained; that is, subsequent changes to a row in the same version do not overwrite earlier changes.

If the table is version-enabled with the VIEW_WO_OVERWRITE hist option specified, this option can later be disabled and re-enabled by calling the SetWoOverwriteOFF Procedure and SetWoOverwriteON Procedure.


This procedure enables the VIEW_WO_OVERWRITE history option that had been disabled by the SetWoOverwriteOFF Procedure.

a)Only the owner of a table can enable versioning on the table.

b)Tables that are version-enabled and users that own version-enabled tables cannot be deleted. You must first disable versioning on the relevant table or tables.

c)Tables owned by SYS cannot be version-enabled.

d)DDL operations are not allowed on version-enabled tables.

e)Index-organized tables cannot be version-enabled.

f)Object tables cannot be version-enabled.

g)A table with one or more columns of LONG data type cannot be version-enabled.


dbms_wm.enableversioning ('TEST');

This will rename the TEST table to TEST_LT(LT stands for Long Transaction ie:Completes over days or week ) and create a view called TEST (which contains original data for more detail refer script of view) addition to this 9 other views will be created.The view uses instead-of triggers to perform all operations against the version enabled table. This hides a lot of the versioning mechanism from the users.
The TEST_LT table has the following additional columns:


Values for following tables when table is version enabled (0,-1,10,!O!)

Test_MV (Materialized view) View it contains data ;which the field is not affected ;with two extra fields WM_MODIFIEDBY and WM_OPTYPE

Test_base view contains the field of original table in addition RID,version,nextver,delstatus,ltlock

Test_BPKC contains fields Rowids of child,parent and base ,childstate ,parentstate ,DS and VER of child,parent & base (ie : 12 fields) if we are in LIVE workspace there will not be an data in it because it is in parent state if it is in any of child workspace there will be data

Test_PKC contains all the fields of Text_BPKC excluding Firstchildver

TEST_HIST This view is created only if ; during table versioning (ie: enableversioning) if we supply hist parameter if hist parameter is NONE then this view will not be there to track history details .

IF active workspace is LIVE then TEST,TEST_BASE,TEST_MV view only have records

Test_conf (Conflict) view contains all fields in Test addition to those wm_workspace,wm_delted

To disable versoning

dbms_wm.disableversioning ('TEST');

To compress WorkSpace


To view curent workspace


SELECT DBMS_WM.isworkspaceoccupied('B_focus_1') FROM DUAL;

To view versionenabled tables

select * from wmsys.wm$table_parvers_view
SELECT * FROM user_wm_versioned_tables;

To  get current version number 

select * from wmsys.WM$CURRENT_VER_VIEW;

To get current and next version 

select * from wmsys.WM$CURRENT_NEXTVERS_VIEW;

To  get current hierarchy of  workspace

select *  from wmsys.WM$CURRENT_HIERARCHY_VIEW;
select *  from wmsys.WM$CONF1_HIERARCHY_VIEW; 

To get parent of a workspace

You should be in a workspace other than LIVE then only we get data from this view ; because for LIVE workspace is parent of  .   
select *  from wmsys.WM$PARENT_HIERARCHY_VIEW; 

To get constraints of version enabled tables 

select * from wmsys.USER_WM_CONSTRAINTS;

To get indexes of version enabled tables

select * from wmsys.USER_WM_IND_COLUMNS;

To get  details of  versionenabled tables that are  modified

select * from wmsys.USER_WM_MODIFIED_TABLES;

To get trigger details on version enabled tables

select * from wmsys.USER_WM_TAB_TRIGGERS;

To get details of locked tables

select * from wmsys.USER_WM_LOCKED_TABLES;

To get   details of  version enabled tables

select * from wmsys.USER_WM_VERSIONED_TABLES;

To get errors in workspace 

select * from wmsys.USER_WM_VT_ERRORS;

To get savepoint  details

 select * from wmsys.USER_WORKSPACE_SAVEPOINTS;

To get foreign key of version enabled tables

 select * from wmsys.USER_WM_RIC_INFO;

To  get current hierarchy and depth of  workspace

 select * from wmsys.ALL_VERSION_HVIEW_WDEPTH;


Mar 13, 2009

Insertion with condition

If there is a table with fields rt (number) which is a primary key and DF varchar2.If there r 10 records and first 5 records r deleted then when inserting records it want to start from 1 and then increment after each insert .

create table DF(DF VARCHAR2(3000),RT NUMBER(2) not null);

alter table DF add constraint E primary key (RT);

insert into df(rt,df)
all_numbers as (select level num from dual connect by level <=99),
available_number as (select num,rownum line from
(select num from all_numbers minus select rt from df order by 1) order by num )
select num,'B-'||rownum from available_number where rownum <=10;


Mar 9, 2009

Unknown Functions

A Word : Risk of using Oracle Undocumented functions or procedures here is that without any notice Oracle may remove them and there will not be support from ORACLE

To get similar characters among the two fields (from 9i onwards)

SELECT merge$actions('lNvl', 'pppl') FROM dual;
SELECT replace(merge$actions(1204, 1260),'BB','') FROM dual;

To view blob details (from 10g onwards)

SELECT sys_op_cl2c(ad_finaltext),s.product_id FROM pm.print_media s

To get blocknumber of a particular tables (from 9i onwards)

select dbms_rowid.rowid_block_number(rowid) from dual;

SELECT COUNT(DISTINCT dbms_rowid.rowid_block_number(rowid)),
COUNT( dbms_rowid.rowid_block_number(rowid))FROM pm.print_media;

To convert into HEX (from 9i onwards)

SELECT sys_op_descend('9')FROM dual;

To show generate null coloumn (from 9i onwards)

SELECT sys_op_lvl(1,21,1,1,1,1 ,2) FROM dual;

To generates and returns a globally unique identifier of 16 bytes The returned data type is RAW(16) (from 9i onwards)

SELECT sys_guid() FROM dual;

To get comma seperated values in rows wise (from 10g onwards)

select sys.odcivarchar2list('Football','Rugby') from dual;

select column_value from table(
select sys.odcivarchar2list('Football','Rugby') from dual);
To get data in ascii characters (from 10g onwards)

SELECT sys_op_c2c(9068986) FROM dual;
TO get number representation of rowid (from 9i onwards)

SELECT rowid, sys_op_rpb(rowid),dbms_rowid.rowid_block_number(rowid) FROM scott.emp
Similar to null (from 10g onwards)

SELECT sys_fbt_insdel, decode(sys_fbt_insdel,null,1,0) FROM dual;
To convert hex to num (from 9i onwards)

SELECT sys_op_rawtonum('000000FF'),UTL_RAW.CAST_FROM_BINARY_INTEGER(255) FROM dual;
To check whether a number is even or odd (from 9i onwards)

Return the value of the bit at position N
The return value is 0 or 1

SELECT sys_op_vecbit('255',0),sys_op_vecbit('255',1),sys_op_vecbit('22',1),sys_op_vecbit('22',0) FROM dual;
Return the binary AND of two hex values (from 9i onwards)

SELECT sys_op_vecand('FC','FD') from dual;
SELECT sys_op_vecand('FF','FD') from dual;
Return the binary OR of two hex values (from 9i onwards)

SELECT sys_op_vecor(('FC'),('FE')) from dual;
Return the binary XOR of two hex values (from 9i onwards)

SELECT sys_op_vecxor(('FF'),('FE')) from dual;
To get ref value visible (from 9i onwards)

SELECT sys_op_r2o(CUSTOMER_REF),CUSTOMER_REF FROM oe.oc_orders WHERE rownum = 1;

Query to show which all values are present in a table and not present

SELECT nvl(to_char(e.EID), column_value||' Not found') empno from table(sys.odcinumberlist(7369,7370,7566,7555,1))l left outer join emp e on e.EID = l.column_value order by 1

sys.odcinumberlist is the default varray that oracle supplies . If you want to create your own type

CREATE TYPE typ_p is varray (32767) of number

SELECT * from table(typ_p(7369,7370,7566,7555,1 ))

To compare null (from 9i onwards)


SELECT 'hi there' FROM DUAL WHERE sys_op_map_nonnull (NULL) = sys_op_map_nonnull (NULL);
SELECT 'hi there' FROM DUAL WHERE nvl(null,'FF')='FF';
select sys_op_map_nonnull(null) from dual; --similat to nvl(null,'FF')
select * from dual where sys_op_map_nonnull(null) = 'FF';
SELECT 'hi there' FROM DUAL WHERE to_char(1||NULL) = to_char(1||NULL);

JSP Format Model

To convert date into numbers and words

select to_char(sysdate,'J') "WORDS" from dual;
select to_date(to_char(sysdate,'J'),'J') "WORDS" from dual;
select to_char(to_date( to_char(sysdate,'J') ,'J'), 'JSP') "WORDS" from dual;

To convert numbers into words

select to_char(to_date(873,'J'), 'JSP') as converted_form from dual;

To convert words into numbers

SELECT LEVEL wordasint FROM dual
AND LEVEL < 124; ---FOR 10 g and above
SELECT sp, n
MEASURES (0 n, sp) RULES ITERATE (86400) UNTIL (TO_CHAR(DATE '0001-01-01' +


Mar 7, 2009

Query Analyzer

To check whether select or DML statements are correct ,here they will not execute (ie: if we check an insert statement it will not insert particular data into that table ) But DDL statement will get executed during parsing itself .

c integer := dbms_sql.open_cursor;
dbms_sql.parse(c, 'select * from scott.emp', dbms_sql.native);
dbms_sql.close_cursor (c);

Mar 2, 2009

Oracle Text - Part 6


manipulate SQL queries by injecting arbitrary SQL code via the THEMES, GIST, TOKENS, FILTER, HIGHLIGHT, and MARKUP procedures


The sectioner object is responsible for identifying the containing section(s) for each text unit. Typically, these sections will be predefined HyperText Markup Language (HTML) or eXtensible Markup Language (XML) sections. Optionally,the sectioner can process all tags as sections delimiters.

For example:

<TITLE>XML Handbook</TITLE>. This allows search between tags using the WITHIN operator. Use of the WITHIN is illustrated in the section on XML searching.

Oracle Text - Part 5

Generating XML Output

The INDEX_STATS procedure supports both formatted text and XML output.The following code
creates the INDEX_STATS report in text format:

-- Table to store our report
CREATE TABLE index_report (id NUMBER(10), report CLOB);

v_report CLOB := null;
report => v_report,part_name => NULL,frag_stats => NULL,
list_size => 20,report_format => NULL);
INSERT INTO index_report (id, report) VALUES (1, v_report);

Then output can be viewed:

SELECT report FROM index_report WHERE id = 1;

To find out the size of the index, we can use the function CTX_REPORT.INDEX_SIZE. This is a function returning a CLOB.

select ctx_report.index_size('SONG_INDEX') from dual;

for a XML report :
SQL> select ctx_report.index_size('SONG_INDEX', null, 'XML') from dual;

This will give us a heap of XML output, including sizes for each object.

Here's a section of the output:

<SIZE_OBJECT_NAME> text_user.SYS_IL0000051565C00006$$

selecting a CLOB, force it into an XMLTYPE value:
select xmltype(ctx_report.index_size('SONG_INDEX', null, 'XML')) from dual;

select extract(xmltype(ctx_report.index_size('SONG_INDEX', null, 'XML')), '//SIZE_OBJECT') from dual;

We're now using the XML DB "extract" function to fetch all of the XML within tags. The syntax '//SIZE_OBJECT' is an XPATH expression meaning "all the XML within a SIZE_OBJECT element anywhere below the root element".the reader is encouraged to look at the tutorial at w3Schools.

select extract(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')),'//SIZE_OBJECT') from dual;

Now specify that only information from the table $I is want . this is done with
within a predicate the xpath expression:

select extract(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')),'//SIZE_OBJECT[SIZE_OBJECT_NAME="text_user.DR$TI$I"]') from dual;

The size in bytes can be get by adding the XPATH expression:

select extract(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')),'//SIZE_OBJECT[SIZE_OBJECT_NAME="text_user.DR$TI$I"]/SIZE_BYTES_USED') from dual;

To avoid tags. There's two ways of doing this 1) the text() function within the XPATH, 2) use extractValue rather than extract.

select extract(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')),'//SIZE_OBJECT[SIZE_OBJECT_NAME="text_user.DR$TI$I"]/SIZE_BYTES_USED/text()') as "Table Size" from dual;

select extractValue(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')), '//SIZE_OBJECT[SIZE_OBJECT_NAME="text_user.DR$TI$I"]/SIZE_BYTES_USED')as "Table Size" from dual;

For fetching ALL the sizes, perhaps to add them together to get a summary XMLSequence can use,which returns a collection of XMLType values. This function can use in a TABLE clause to unnest the collection values into multiple rows. Now that we're generating a "table", we no longer need to reference DUAL.

To get just the sizes:

select * from table(xmlsequence( extract(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')),'//SIZE_OBJECT/SIZE_BYTES_USED')));

To get all the object info, one object per row:

select * from table(xmlsequence( extract(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')), '//SIZE_OBJECT')));

Processing information into individual values:

select extractValue(Column_Value, '/SIZE_OBJECT/SIZE_OBJECT_NAME') as "Name",
extractValue(Column_Value, '/SIZE_OBJECT/SIZE_TABLESPACE_NAME') as "Tablespace",
extractValue(Column_Value, '/SIZE_OBJECT/SIZE_BYTES_USED') as "Bytes"
from table(xmlsequence(extract(xmltype(replace(ctx_report.index_size('SONG_INDEX', null, 'XML'),chr(10),'')),'//SIZE_OBJECT')));

To get sum of all the sizes to get an aggragate total size of all objects
used in the index.

select sum(extractValue(Column_Value, '/SIZE_OBJECT/SIZE_BYTES_USED')) "Total"
from table(xmlsequence(extract(xmltype(replace(ctx_report.index_size('ti', null, 'XML'),chr(10),'')),'//SIZE_OBJECT')));


Most of the CTX_REPORT procedures have two forms - a function which returns a CLOB (as done above)and an alternate form which requires to pass in a CLOB to be populated. One procedure - INDEX_STATS - does not have a function version. This is because it needs to do a full table scan of the main index table, which is likely to take some time.Therefore when calling INDEX_STATS it is needed to go about things a little differently. First create a table with an XMLType column. Then call a PL/SQL block which passes a temporary CLOB to CTX_REPORT, and then inserts that CLOB into the XMLType column. Then various XML operations can perform on that table.

create table output(report XMLType);

tlob clob;
ctx_report.index_stats(index_name=>'ti', report=>tlob,
list_size=>20, report_format=>'XML');
insert into output values (xmlType (replace(tlob,chr(10),'')) );

There is a single row in table OUTPUT, which contains XML report. First well get the
estimated row fragmentation:

select extractValue(report,'//STAT_STATISTIC[@NAME="estimated row fragmentation"]')
as "Fragmentation" from output;

Now get the top three most frequent tokens.

using the position function:

select extract(value(d), '//STAT_TOKEN_TEXT')
from output, table(xmlsequence(extract(report,'/CTXREPORT/INDEX_STATS/STAT_TOKEN_STATS/STAT_TOKEN_LIST[@NAME="most frequent tokens"]/
STAT_TOKEN[position()<4]'))) d; Conclusion
The XML output mode of CTX_REPORT allows powerful manipulation of index information. In order to make full use of these,a good understanding of the XML features of the Oracle database, such as extract, extractValue, XMLSequence, and of XPATH syntax in general is needed.With the use of XML exploding within the data processing world, such an understanding is likely to be very useful in the future.

Oracle Text - Part 4

Progressive Relaxation is a new technique for text searching, available with Oracle 10g.

It assumes a basic working knowledge of Oracle Text, such as the operators used
in query expressions.When Would Use It?

First, let's consider a search scenario.

You have a web site selling books. A user searches for "Michael Crichton" in the "search author" box. OK, easy enough. You do the search, and return the top 10 hits (or whatever) that match the search criteria.

But what if the user mis-spells the firstname, and searches for "Michel Crichton"? In this case, a good strategy for handling this might be to find the top 10 hits from these searches:

1. Any books where the author is exactly "Michel Crichton"
2. Any books containing a fuzzy match of each word, in the right order
3. Any books having either exact word
4. Any books having a fuzzy match of either word.

Of course we can do this in a search like

select book_id from books where contains (author, '(michel crichton) OR (?michel ?crichton) OR (michel OR crichton) OR (?michel OR ?crichton)

But there are two problems with this search:

1. From the user's point of view, hits which are a poor match will be mixed in with hits which are a good match. The user wants to see good matches displayed first.
2. From the system's point of view, the search is inefficient. Even if there were plenty of hits for exactly "Michel Crichton", it would still have to do all the work of the fuzzy expansions and fetch data for all the rows which satisfy the query.

An alternative is to run four separate queries. This way, we can do the exact search first, and then only run the queries with more relaxed criteria if they are needed to get enough hits for the results page.

But apart from the inefficiency of (potentially) running multiple queries, we need to de-duplicate the results. The "relaxed" queries will in many cases hit the rows returned by the exact queries. To avoid duplicates in the result set, the application must screen these hits out, a potentially expensive task in terms of programming and maintenance,if not raw performance.

To solve this problem, Oracle Text in Oracle Database 10g introduces "progressive relaxation".This allows you to specify the different searches to run, and Oracle will run each in turn,returning de-duplicated results until the application stops fetching hits.

The scores returned are manipulated such that if you order by score


The benefits of progressive relaxtion is that an application developer can specify operations to be applied to a user query in a declarative manner. It is not necessary to parse the query and apply operators to each search term - the developer just specifies what options should be applied to each term, and how they should be combined (eg AND or OR)

The application also benefits from automatic de-duplication of results at a very early stage in the query (before docid to rowid translation) which is much more efficient than doing it at the final stage, as you would have to if you were running multiple queries.

Query Templates

The actual implementation of progressive relaxation is via the query template mechanism. If you have not come across this before, don't worry - it's quite straightforward and the examples should make it clear. Basically a query template is an XML fragment that is used in the CONTAINS clause in place of a simple query string.

There are some other things that you can do with query templates, such as specifying
language, query grammars and scoring options, but we won't be covering them here.

So - on to our first example:

create table mybooks (title varchar2(20), author varchar2(20));

insert into mybooks values ('Consider the Lillies', 'Ian Crichton Smith');
insert into mybooks values ('Sphere', 'Michael Crichton');
insert into mybooks values ('Stupid White Men', 'Michael Moore');
insert into mybooks values ('Lonely Day', 'Michaela Criton');
insert into mybooks values ('How to Teach Poetry', 'Michaela Morgan');

create index auth_idx on mybooks (author) indextype is ctxsys.context;

SELECT score(1), title, author FROM mybooks WHERE CONTAINS (author, '
<seq>michael crichton </seq>
<seq>?michael ?crichton </seq>
<seq>michael OR crichton </seq>
<seq>?michael OR ?crichton </seq>
</query>', 1) > 0 ORDER BY score(1) DESC;

The output of this query is:

---------- -------------------- --------------------
76 Sphere Michael Crichton
51 Lonely Day Michaela Criton
26 Stupid White Men Michael Moore
26 Consider the Lillies Ian Crichton Smith
1 How to Teach Poetry Michaela Morgan

It can see that the first line is an exact match, according to the first entry in our progression sequence. The second line corresponds to a fuzzy match of each term in order - our second criteria. The third and fourth rows come from the exact "micheal OR chrichton" and finally the last row has a single match which is a fuzzy hit on one of the terms.

Obviously in this example, it is fetching all the rows, so there is no major advantage in using progressive relaxation. We can limit it to only return the first two hits, using a PL/SQL cursor:

set serveroutput on format wrapped

max_rows integer := 2;
counter integer := 0;
-- do the headings
dbms_output.put_line(rpad('Score', 8)||rpad('Title', 20)||rpad('Author', 20));
dbms_output.put_line(rpad('-----', 8)||rpad('-----', 20)||rpad('------', 20));
-- loop for the required number of rows
for c in (select score(1) scr, title, author from mybooks where contains (author, '
<seq>michael crichton </seq>
<seq>?michael ?crichton </seq>
<seq>michael OR crichton </seq>
<seq>?michael OR ?crichton </seq>
</query>', 1) > 0) loop
dbms_output.put_line(rpad(c.scr, 8)||rpad(c.title, 20)||rpad(, 20));
counter := counter + 1;
exit when counter >= max_rows;
end loop;

The output from this is

Score Title Author
----- ----- ------
76 Sphere Michael Crichton
51 Lonely Day Michaela Criton

Now theres one more feature an application designer might want. And thats to
stop the search after it has evaluated the first successful search criteria. So in our example, if we get one or more hits on exactly "michael chrichton", we dont want to try any of the other searches. If the exact search fails, we want to try the others only until one of them returns one or more rows.

Theres (currently) no way to do this as part of the query template syntax.However, it is possible to do this at the application level by looking at the scores returned using PLSQL

Score Title Author
----- ----- ------
76 Sphere Michael Crichton
51 Lonely Day Michaela Criton
26 Stupid White Men Michael Moore
26 Consider the Lillies Ian Crichton Smith
1 How to Teach Poetry Michaela Morgan

Now, given that the maximum score of a text query is 100, and that we had four steps in our search, we might be able to notice something here. Specifically, any match on the first step will always score in the top quarter of the possible results - 76% to 100%. The next step will score in the range 51-75%, the next 26-50%, and the final step 1-25%. If we had had five steps in our query, the scores would have been in the ranges 81-100%, 61-80%, 41-60%, 21-40% and 1-20%.

So in order to stop our results after the first valid search, we need to detect the score crossing one of these boundaries. In order to do this we MUST know in advance how many stepsthere are. The PL/SQL for all this is a little more tricky than before:

max_rows integer := 2;
counter integer := 0;
number_of_steps integer := 4;
score_range_size integer; -- 33 for 3 steps, 25 for 4, 20 for 5 etc
this_score_group integer; -- final step is 1, penultimate step is 2 ...
last_score_group integer := 0; -- to compare change
-- do the headings
dbms_output.put_line(rpad('Score', 8)||rpad('Title', 20)||rpad('Author', 20));
dbms_output.put_line(rpad('-----', 8)||rpad('-----', 20)||rpad('------', 20));
for c in (select score(1) scr, title, author from mybooks where contains (author, '
<seq>michael crichton </seq>
<seq>?michael ?crichton </seq>
<seq>michael OR crichton </seq>
<seq>?michael OR ?crichton </seq>
</query>', 1) > 0) loop
score_range_size := 100/number_of_steps;
this_score_group := c.scr/score_range_size;
exit when this_score_group < last_score_group;
last_score_group := this_score_group;
dbms_output.put_line(rpad(c.scr , 8)||rpad(c.title, 20)||rpad(, 20));
counter := counter + 1;
exit when counter >= max_rows;
end loop;

The output from this is:

Score Title Author
----- ----- ------
76 Sphere Michael Crichton

We could add a new, stricter step (remembering to increase the number_of_steps variable).This won't actually find anything but will demonstrate that the procedure continues until it does find at least one row:

number of steps number := 5;
<seq>michael crichton </seq>
<seq>?michael ?crichton </seq>
<seq>michael OR crichton </seq>
<seq>?michael OR ?crichton </seq>

and output would be:

Score Title Author
----- ----- ------
61 Sphere Michael Crichton

there is a simplification which makes life easier for the application developer.
Generating the full syntax above can be complicated to program. So there is a "shorthand" syntax, known as a "query rewrite template":

<textquery> michael crichton
<seq><rewrite>transform((TOKENS, "{", "}", " "))</rewrite></seq>
<seq><rewrite>transform((TOKENS, "?{", "}", " "))</rewrite></seq>
<seq><rewrite>transform((TOKENS, "{", "}", "OR"))</rewrite></seq>
<seq><rewrite>transform((TOKENS, "?{", "}", "OR"))</rewrite></seq>

This will generate the same four-step syntax as used above. The arguments after TOKENS are as follows:

* Prefix - what to put before each token
* Suffix - what to put after each token
* Connector - an operator to link each token. Space causes a phrase search.

It is usually a good idea to surround each term with braces "{}", in case the user has entered a reserved word like STEM or NT. Beware, though, that adding a wild card after a brace can have strange effects - {dog}% is not the same as dog%.

Oracle Text - Part 3

CTXCAT indexes work best when text is in "small chunks" - maybe a couple of lines maximum - and searches need to restrict and/or sort the result set according to certain structured criteria - usually numbers or dates.

For example,consider an on-line auction site. Each item for sale has a short
description, a current bid price and dates for the start and end of the auction. A
user might want to see all the records with a
current bid price less than $500. Since he's particularly interested in new items, he wants the results sorted by auction start time.

Such a search would be fairly inefficient using a normal CONTEXT index. The kernel would have to find all the records that matched the text search, then restrict the set to those with the correct price (which requires the use of a different index), and then sort the results using a third index.

By including structured information such as price and date within the CTXCAT index, we are able to make this search very much more efficient.When is a CTXCAT index NOT suitable?

The query language with CTXCAT is considerably simpler than for CONTEXT indexes. Basically, you can search for phrases and words (with wild cards if required), using AND and OR operators. If your application needs more complex text retrieval featurs - such as stemming, thesaurus, fuzzy matching and so on, you should be using a CONTEXT index.

There are also differences in the time and space needed to create the index. CTXCAT indexes take quite a bit longer to create - and use considerably more disk space - than CONTEXT indexes. If you are tight on disk space, you should consider carefully whether CTXCAT indexes are appropriate for you.Any other differences?

Yes - in DML processing (updates, inserts and deletes).CTXCAT indexes are transactional.Where a CONTEXT index uses a "deferred indexing" method - CTXCAT indexes work much more like a normal (b-tree) index. When you commit changes, all necesary changes to the CTXCAT indexes take place before the commit returns

CREATE INDEX indexname ON table(column) INDEXTYPE IS CTXCAT;

create table auction (
item_id NUMBER PRIMARY KEY, -- auction item identifier
item_desc VARCHAR2(80), -- free-form item description
price NUMBER, -- current price of the item
start_time DATE -- end time of the auction
end_time DATE -- end time of the auction

A CTXCAT index (like a CONTEXT index) is a "domain" index. Therefore it supports the
"PARAMETERS" clause. A number of possible parameter settings are shared with CONTEXT indexes.These are: LEXER, MEMORY, STOPLIST, STORAGE and WORDLIST (no other CONTEXT parameters are supported). Howevwer, the most important parameter is a new one: INDEX SET.

INDEX SET defines the structured columns that are to be included in the CTXCAT index. if I want to create an index on the item_desc column, but I need to be able to limit my search results by price, and sort by start_time. I do this by creating a new INDEX SET, and adding the structured columns to it.CTX_DDL package allow to do this:

ctx_ddl.add_index ('auction_set', 'price');
ctx_ddl.add_index ('auction_set', 'start_time');

Note that the item_desc column is NOT part of the INDEX SET. item_desc is only mentioned when we come to create the actual index:

CREATE INDEX auction_index ON auction (item_desc)
PARAMETERS ('INDEX SET auction_set');

how to search ?

By using the CATSEARCH operator instead of the CONTAINS operator used for
a CONTEXT index.If i want to find all auction items which contains the words "toy" and "dog" but not
the phrase "live animal":

SELECT item_id, item_desc FROM auction
WHERE CATSEARCH (item_desc, '(toy dog) | "live animal"', null) > 0;

A few points to note:

* ANDed terms do not need the word AND or even an "&" operator. AND is assumed between
any adjacent terms.
* NOT is represented by "|" (OR, not used here, is represented by "|")
* Parentheses can be used to group terms
* Double quotes are used to surround a phrase (otherwise "live animal" would have been
read as "live AND animal".

The "null" in the query above is a placeholder for a structured clause. There is no default -
if no structured clause is provided "null" Must be used here.

The structured clause allows to restrict, or sort,the results.the query can be extended
above to find only items costing less than $100,

WHERE CATSEARCH (item_desc, '(toy dog) | "live animal"', 'price < 100') > 0

and want to find the results with the newest items first

WHERE CATSEARCH (item_desc, '(toy dog) | "live animal"',
'price < 100 order by start_time desc') > 0

It is worth noting that the creation of the B-Tree indexes will be considerably quicker if the SORT_AREA_SIZE kernel parameter is increased. The default is 64K - a very low figure. Increasing this to 1MB will have a very significant effect - by doing this index-creation times reduce by a factor of 10 . However note the specified amount of memory will be used by EVERY process connecting, so great care should be taken with this parameter if the database is shared with many other users. It might be possible to increase it just for index creation, then reduce it later.