RE: question about index
Date: Mon, 19 May 2008 13:38:28 -0700 (PDT)
Message-ID: <4291.54462.qm@web56601.mail.re3.yahoo.com>
Hi,
Its a function based index and unfortunately, it will never be used. Below is a detailed test case:
SQL> desc t
Name Null? Type ----------------------------------------------------- -------- -------------------------------- ID NUMBER NAME VARCHAR2(4000)
SQL> create index t_idx1 on t('garbage');
Index created.
SQL> set line 10000
SQL> exec dbms_stats.gather_table_stats( user, 't');
PL/SQL procedure successfully completed.
SQL> select index_name, INDEX_TYPE, num_rows from user_indexes where table_name = 'T';
INDEX_NAME INDEX_TYPE NUM_ROWS
------------------------------ --------------------------- ----------
T_IDX1 FUNCTION-BASED NORMAL 6000
SQL> select index_name, column_expression from user_ind_expressions where table_name = 'T';
INDEX_NAME COLUMN_EXPRESSION
------------------------------ -----------------------------------------------------------------
-
T_IDX1 'garbage'
Regards
Asif Momen
http://momendba.blogspot.com
"Terrian, Thomas J Mr CTR DLA J6DIB" <Tom.Terrian.ctr_at_dla.mil> wrote: Function based index......but I am not sure how you would use it.
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Sent: Monday, May 19, 2008 1:55 PM
To: oracle-l_at_freelists.org
Subject: question about index
Ok i guess i'm having a brain fart, someone asked me about this and for the life of me i can't figure it out. The 2nd index, what exactly is it doing with single quotes around the column name??
SQL> create table z1(x1 number, x2 date);
Table created.
SQL> CREATE INDEX X1 ON Z1 (X1); Index created.
SQL> CREATE INDEX X2 ON Z1 ('X1'); Index created.
Thanks, Joe
You can have it: Fast, Right or Cheap, pick 2 of the 3. Fast + Right is Expensive
Fast + Cheap will be incorrect.
Right + Cheap will take a while.
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Received on Mon May 19 2008 - 15:38:28 CDT