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Chris Saxon

Thanks for the question.

Asked: January 06, 2021 - 3:15 pm UTC

Last updated: January 08, 2021 - 1:46 pm UTC

Version: 12.1

Viewed 100+ times

You Asked

Dear team,

I hope you are all doing good!

I wanted to ask for some hints to fix the following problem:
We have a huge dataset (>60 mio) of items. Each item has an item number. The item number has the datatype varchar2(50).
The format of the item number vary from vendor to vendor [refer to line 03-07 in the example below].
It is quite hard for a user who is searching for an item to have the correct notation in mind.
To support the searching for item numbers we want to skip all these characters './,=?{}\()[]-;~|$!>*%_&' [refer to line 16 in the example below].

This is our first solution which is sadly not working as expected:
------------------------------------------------------------------
/*line: 01*/ /*** PREPARATION ***/
/*line: 02*/ create table test_item_number (item_number varchar2(50));
/*line: 03*/ insert into test_item_number values ('1.234.5');
/*line: 04*/ insert into test_item_number values ('1-25466');
/*line: 05*/ insert into test_item_number values ('001/007');
/*line: 06*/ insert into test_item_number values ('AA.123');
/*line: 07*/ insert into test_item_number values ('ABC.PD');
/*line: 08*/ commit;
/*line: 09*/ 
/*line: 10*/ /*** DOMAIN PREFERENCES ***/
/*line: 12*/ --grant execute on ctx_ddl to hr (if necessary);
/*line: 13*/ BEGIN
/*line: 14*/     --LEXER
/*line: 15*/  ctx_ddl.create_preference('MyLexer', 'BASIC_LEXER');
/*line: 16*/  ctx_ddl.set_attribute('MyLexer' , 'SKIPJOINS','./,=?{}\()[]-;~|$!>*%_&');
/*line: 17*/  
/*line: 18*/  --WORDLIST
/*line: 19*/  ctx_ddl.create_preference('MyWordList', 'BASIC_WORDLIST');
/*line: 20*/  ctx_ddl.set_attribute('MyWordList','PREFIX_INDEX','TRUE');    
/*line: 21*/  ctx_ddl.set_attribute('MyWordList','PREFIX_MIN_LENGTH', '2');
/*line: 22*/  ctx_ddl.set_attribute('MyWordList','PREFIX_MAX_LENGTH','50');
/*line: 23*/  ctx_ddl.set_attribute('MyWordList','SUBSTRING_INDEX','YES');
/*line: 24*/    ctx_ddl.set_attribute('MyWordList','REVERSE_INDEX','TRUE'); 
/*line: 25*/ END;
/*line: 26*/ /*** DOMAIN INDEX ***/
/*line: 27*/ create index IDX_ITEM_NUMBER 
/*line: 28*/           on test_item_number(item_number)
/*line: 29*/        indextype is ctxsys.context
/*line: 30*/   parameters ('LEXER MyLexer WORDLIST  MyWordList SYNC (ON COMMIT)');

------------------------------------------------------------------
This results in the following search problem:
select * from test_item_number where contains(item_number, 'AA1%') >0; -- 0 rows
select * from test_item_number where contains(item_number, '1234%') >0; -- 0 rows

The create domain index still include the dots ('.'). Here is the created index table '$i' (including my thought what can be the reason for this):
--show index entries
select token_text from dr$idx_item_number$i;
reult:
00
001
0010
00100
001007
001007
1. --because of numjoin?
1.2
1.23
1.234
1.234.
1.234.5
1.234.5
12
123
123
125
1254
12546
125466
125466
AA --because of punctuations?
AA
AB
ABC
ABCP
ABCPD
ABCPD

To aviod dots ('.') in the index I was trying this workarounds:
------------------------------------------------------------------
/*** WORKAROUND 1 (NOT WORKING) ***/
create index IDX_ITEM_NUMBER_REPLACE 
          on test_item_number(replace(item_number,'.',''))
       indextype is ctxsys.context
  parameters ('LEXER     MyLexer 
      WORDLIST  MyWordList
      SYNC      (ON COMMIT)');
--error: DRG-11304: function-based indexes are not supported by this indextype.

/*** WORKAROUND 2 (NOT WORKING) ***/
BEGIN
  --LEXER
  ctx_ddl.set_attribute('MyLexer' , 'NUMJOIN',' ');
  ctx_ddl.set_attribute('MyLexer' , 'PUNCTUATIONS',' ');
END;
drop index IDX_ITEM_NUMBER;
create index IDX_ITEM_NUMBER 
          on test_item_number(item_number)
       indextype is ctxsys.context
  parameters ('LEXER MyLexer WORDLIST  MyWordList SYNC (ON COMMIT)');
--the index entries (dr$idx_item_number$i) are the same like above 

------------------------------------------------------------------

Regarding this problem I have the following questions:
(1) Are my thoughts correct why the domain index includes the dots ('.') - because of numjoin/punctuations?
(2) Is there anything else i can do in the domain index preferences to avoid indexing any dot ('.')?
(3) If there is no solution for question 2, is there another easy workaround (maybe without invisible or virtual columns)?
(4) I can also use a normal index but then the left-truncated wildcard queries will be very slow - or can I also improve this in the normal index?

THANK you very much for you thoughts!

Have a great day,
Walter

and we said...

I reached out to Roger Ford, PM for Oracle Text on this. He had this to say:

Workaround 2 works - setting NUMJOIN to an empty string; shouldn't be necessary to change PUNCTUATIONS in this example.

It's best if you only look at TOKEN_TYPE=0 when listing the contents of $I - saves confusion with the prefix index stuff which is TOKEN_TYPE=6.

The first workaround won't work as-is because you can't create a domain index directly on a function. However, you can use a function as part (or all) of the COLUMNS list in a MULTI_COLUMN_DATASTORE.


And provided these test cases:

Case 1

create table test_item_number (item_number varchar2(50));
insert into test_item_number values ('1.234.5');
insert into test_item_number values ('1-25466');
insert into test_item_number values ('001/007');
insert into test_item_number values ('AA.123');
insert into test_item_number values ('ABC.PD');
commit;

/*** DOMAIN PREFERENCES ***/
--grant execute on ctx_ddl to hr (if necessary);
BEGIN
    --LEXER
 ctx_ddl.create_preference('MyLexer', 'BASIC_LEXER'); 
 ctx_ddl.set_attribute('MyLexer' , 'SKIPJOINS','./,=?{}\()[]-;~|$!>*%_&');
 ctx_ddl.set_attribute('MyLexer' , 'NUMJOIN',' ');

 --WORDLIST
 ctx_ddl.create_preference('MyWordList', 'BASIC_WORDLIST');
 ctx_ddl.set_attribute('MyWordList','PREFIX_INDEX','TRUE');    
 ctx_ddl.set_attribute('MyWordList','PREFIX_MIN_LENGTH', '2');
 ctx_ddl.set_attribute('MyWordList','PREFIX_MAX_LENGTH','50');
 ctx_ddl.set_attribute('MyWordList','SUBSTRING_INDEX','YES');
--   ctx_ddl.set_attribute('MyWordList','REVERSE_INDEX','TRUE'); 
END;
/

/*** DOMAIN INDEX ***/
create index IDX_ITEM_NUMBER 
          on test_item_number(item_number)
       indextype is ctxsys.context
  parameters ('LEXER MyLexer WORDLIST  MyWordList SYNC (ON COMMIT)');

--show index entries
select token_text from dr$idx_item_number$i where token_type = 0;

TOKEN_TEXT   
001007        
12345         
125466        
AA123         
ABCPD

select * from test_item_number
where  contains ( item_number, '1234%' ) > 0;

ITEM_NUMBER   
1.234.5   

select * 
from   test_item_number 
where  contains ( item_number, 'AA1%' ) > 0; 

ITEM_NUMBER   
AA.123     


Case 2

/*** PREPARATION ***/
create table test_item_number (item_number varchar2(50));
insert into test_item_number values ('1.234.5');
insert into test_item_number values ('1-25466');
insert into test_item_number values ('001/007');
insert into test_item_number values ('AA.123');
insert into test_item_number values ('ABC.PD');
commit;

/*** DOMAIN PREFERENCES ***/
--grant execute on ctx_ddl to hr (if necessary);
BEGIN
    --LEXER
 ctx_ddl.create_preference('MyLexer', 'BASIC_LEXER'); 
 ctx_ddl.set_attribute('MyLexer' , 'SKIPJOINS','./,=?{}\()[]-;~|$!>*%_&');

 --WORDLIST
 ctx_ddl.create_preference('MyWordList', 'BASIC_WORDLIST');
 ctx_ddl.set_attribute('MyWordList','PREFIX_INDEX','TRUE');    
 ctx_ddl.set_attribute('MyWordList','PREFIX_MIN_LENGTH', '2');
 ctx_ddl.set_attribute('MyWordList','PREFIX_MAX_LENGTH','50');
 ctx_ddl.set_attribute('MyWordList','SUBSTRING_INDEX','YES');
-- only in recent versions:   ctx_ddl.set_attribute('MyWordList','REVERSE_INDEX','TRUE'); 
 ctx_ddl.create_preference('MyDatastore', 'MULTI_COLUMN_DATASTORE');
 ctx_ddl.set_attribute('MyDatastore', 'COLUMNS', 'replace(ITEM_NUMBER,''.'','''')');
 ctx_ddl.set_attribute('MyDatastore', 'DELIMITER', 'newline'); /* avoid adding a tag */
END;
/

/*** DOMAIN INDEX ***/
create index IDX_ITEM_NUMBER 
          on test_item_number(item_number)
       indextype is ctxsys.context
  parameters ('LEXER MyLexer WORDLIST  MyWordList DATASTORE MyDatastore SYNC (ON COMMIT)');

--show index entries
select token_text from dr$idx_item_number$i where token_type = 0;

TOKEN_TEXT   
001007        
12345         
125466        
AA123         
ABCPD 

select * from test_item_number
where  contains ( item_number, '1234%' ) > 0;

ITEM_NUMBER   
1.234.5 

select * 
from   test_item_number 
where  contains ( item_number, 'AA1%' ) > 0; 

ITEM_NUMBER   
AA.123    

Rating

  (1 rating)

Comments

A reader, January 07, 2021 - 7:57 pm UTC

Dear team,

first of all: Thank you very much for your fast feedback!

We are now working with your second suggestion (case 2) - very nice.

Sadly your Case 1 ist not working on my end. Here is the result:
/*** YOUR CASE 1 (MY WORKAROUND 2): NOT WORKING) ***/
/*** DOMAIN PREFERENCES ***/
BEGIN
  --LEXER
  --ctx_ddl.drop_preference('MyLexer');
  ctx_ddl.create_preference('MyLexer', 'BASIC_LEXER');
  ctx_ddl.set_attribute('MyLexer' , 'SKIPJOINS','./,=?{}\()[]-;~|$!>*%_&');
  ctx_ddl.set_attribute('MyLexer' , 'NUMJOIN',' ');
 
  --WORDLIST
  --ctx_ddl.drop_preference('MyWordList');
  ctx_ddl.create_preference('MyWordList', 'BASIC_WORDLIST');
  ctx_ddl.set_attribute('MyWordList','PREFIX_INDEX','TRUE');    
  ctx_ddl.set_attribute('MyWordList','PREFIX_MIN_LENGTH', '2');
  ctx_ddl.set_attribute('MyWordList','PREFIX_MAX_LENGTH','50');
  ctx_ddl.set_attribute('MyWordList','SUBSTRING_INDEX','YES');
  ctx_ddl.set_attribute('MyWordList','REVERSE_INDEX','TRUE'); 
END;
/
/*** DOMAIN INDEX ***/
drop index IDX_ITEM_NUMBER
/
create index IDX_ITEM_NUMBER 
          on test_item_number(item_number)
       indextype is ctxsys.context
  parameters ('LEXER MyLexer WORDLIST  MyWordList SYNC (ON COMMIT)')
/

select token_text from dr$idx_item_number$i where token_type = 0;

TOKEN_TEXT
001007
1.234.5
123
125466
AA
ABCPD

select * from test_item_number where contains(item_number, 'AA1%')  >0; -- 0 rows
select * from test_item_number where contains(item_number, '1234%') >0; -- 0 rows


But I have to say that I am using Oracle 19c for this testing (we want to upgrade soon). Could this be the reason?

Anyways thanks for your help!

Have a nice day,
Walter
Chris Saxon
January 08, 2021 - 1:46 pm UTC

I ran the test case on 19.6 & 21.1 and got the expected result - the rows are returned in both cases.

Have you definitely dropped and re-created the lexer and word list?

If so you may be hitting a platform-specific bug; you'll need to take this up with support.

Note - While there's lots of cool stuff in 21c worth upgrading for, it's an innovation release. This means you'll only get two years' of support.

19c is the current long term release. This has a longer support window.

If you're able to upgrade regularly (e.g. every 1-2 years), I'd recommend going for it. Many customers aren't in this position though, making 19c the better bet (for now).

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