DB2 FOR LUW / DB2FORLUW / B10 - DB2

There are some situations where indexes on column-organized
tables can provide significant performance improvements but they
are not chosen by the optimizer.

For example:
create table tc1 (pk1 int not null, pk2 int not null, c1 int, c2
int, c3 int) organize by column;
create unique index tc1pk on tc1 (pk1,pk2);

select * from tc1 where exists (
select c1 from tc1 g where g.pk1 = tc1.pk1
group by pk1,c1 having count_big(*) >= 1000)
order by pk1,pk2;

Index TC1PK  might've been a faster way to access table TC1 in
the EXISTS subquery, depending on the data characteristics.

The issue tends to occur when the potential index access occurs
in sub-selects or sub-queries.

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* USERS AFFECTED:                                              *
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* PROBLEM DESCRIPTION:                                         *
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* RECOMMENDATION:                                              *
* Upgrade to Db2 11.1 Mod 4 Fixpack 4 or higher                *
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Use an optimization guideline to force the desired index access.

not known / see Local fix

Date  - problem reported    :
Date  - problem closed      :
Date  - last modified       :

13.09.2018
27.11.2018
27.11.2018