RE: oracle equivalent of teradata's sparse index

Could you use a function-based index ? Something like this

create table t (n number, d date, v varchar2 (20)) nologging ;
insert /*+ append */ into t  (n, d, v)
  select rn as n, sysdate - rn as d, dbms_random.string ('p', 20) as v
   from (select rownum as rn from dual connect by level <= 200000) ;
create index ti_1 on t (n) ;
create index ti_2 on t (case when d >= DATE '2010-01-01' then n else null end) ;
select index_name, num_rows, leaf_blocks
 from user_indexes
 where index_name in ('TI_1', 'TI_2')
 order by 1 ;

Proof of concept:

SQL> create table t (n number, d date, v varchar2 (20)) nologging ;
Table crÚÚe.
SQL> insert /*+ append */ into t  (n, d, v)
  2    select rn as n, sysdate - rn as d, dbms_random.string ('p', 20) as v
  3     from (select rownum as rn from dual connect by level <= 200000) ;
200000 ligne(s) crÚÚe(s).
SQL> commit ;
Validation effectuÚe.

SQL> create index ti_1 on t (n) ;
Index crÚÚ.
SQL> create index ti_2 on t (case when d >= DATE '2010-01-01' then n else null e
nd) ;
Index crÚÚ.

SQL> analyze table t compute statistics for table for all indexes ;
Table analysÚe.

SQL> select index_name, num_rows, leaf_blocks
  2   from user_indexes
  3   where index_name in ('TI_1', 'TI_2')
  4   order by 1 ;
INDEX_NAME                       NUM_ROWS LEAF_BLOCKS
------------------------------ ---------- -----------
TI_1                               200000         445
TI_2                                  213           1

SQL>

De : oracle-l-bounce@xxxxxxxxxxxxx [mailto:oracle-l-bounce@xxxxxxxxxxxxx] De la 
part de dd yakkali
Envoyé : lundi 2 août 2010 16:36
À : oracle-l@xxxxxxxxxxxxx
Objet : oracle equivalent of teradata's sparse index

hello dbas,

Some one asked me that teradata can create index for only a subset of rows of a 
table. We have a huge table (5 billion) which is for few months of data but the 
data for most part is accessed for yesterday. So the question is: is there any 
way to create index only for yesterday.

Google did not come up wth any hits.

thanks
Deen

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