Partition pruning doesn't work

Question

Hi all,
in this query I've joined 3 tables, each of them partitioned along the field PARTITION_KEY_PRE:
SELECT *
FROM t_cp_pp_basdat basdat LEFT OUTER JOIN t_cp_pp_custom custom
ON basdat.pre_processing_id = custom.pre_processing_id
AND basdat.partition_key_pre = custom.partition_key_pre
AND basdat.customer_unique_id_f = custom.customer_unique_id_f
LEFT OUTER JOIN t_cp_pp_groups groups
ON basdat.partition_key_pre = groups.partition_key_pre
AND basdat.pre_processing_id = groups.pre_processing_id
AND custom.customer_group_id = groups.customer_group_id
WHERE basdat.partition_key_pre = '111100361A0700';
The problem is that the T_CP_PP_GROUPS table don't prune; if I remove the condition
custom.customer_group_id = groups.customer_group_id
the prune works, but obviously the query is wrong. Here it is the explain plan
Operation                    Object Name          Cost     Object Node     In/Out     PStart          PStop
SELECT STATEMENT Optimizer Mode=ALL_ROWS               6156                     
PX COORDINATOR                                        
PX SEND QC (RANDOM)          SYS.:TQ10003          6156      :Q1003          P->S      QC (RANDOM)
HASH JOIN OUTER                         6156      :Q1003          PCWP           
PX RECEIVE                              50      :Q1003          PCWP           
PX SEND PARTITION (KEY)          SYS.:TQ10002          50      :Q1002          P->P      PART (KEY)     
VIEW                              50      :Q1002          PCWP           
HASH JOIN RIGHT OUTER BUFFERED               50      :Q1002          PCWP           
PX RECEIVE                         5      :Q1002          PCWP           
PX SEND HASH          SYS.:TQ10000          5      :Q1000          P->P      HASH      
PX BLOCK ITERATOR                    5      :Q1000          PCWC      KEY     KEY
TABLE ACCESS FULL     TUKB103.T_CP_PP_CUSTOM     5      :Q1000          PCWP      466     466
PX RECEIVE                         44      :Q1002          PCWP           
PX SEND HASH          SYS.:TQ10001          44      :Q1001          P->P      HASH      
PX BLOCK ITERATOR                    44      :Q1001          PCWC      KEY     KEY
TABLE ACCESS FULL     TUKB103.T_CP_PP_BASDAT     44      :Q1001          PCWP      1437     1437
PX PARTITION LIST ALL                         6013      :Q1003          PCWC      1     635
TABLE ACCESS FULL          TUKB103.T_CP_PP_GROUPS     6013      :Q1003          PCWP      1     635
Can anyone help me to tune this query?
Thanks,
Davide

Answer 1

Please learn to use { code } tags. Since that makes you code to read much better in the forum. See the FAQ for further instructions on that.
About the pruning question.
You could experiment with different types of joins.
a) Join the GROUPS table with the columns from CUSTOM
SELECT *
FROM t_cp_pp_basdat basdat
LEFT OUTER JOIN t_cp_pp_custom custom
   ON basdat.pre_processing_id = custom.pre_processing_id
   AND basdat.partition_key_pre = custom.partition_key_pre
   AND basdat.customer_unique_id_f = custom.customer_unique_id_f
LEFT OUTER JOIN t_cp_pp_groups groups
  ON custom.partition_key_pre = groups.partition_key_pre
  AND custom.pre_processing_id = groups.pre_processing_id
  AND custom.customer_group_id = groups.customer_group_id
WHERE basdat.partition_key_pre = '111100361A0700'; b) Put the partion key into each on clause.
SELECT *
FROM t_cp_pp_basdat basdat
LEFT OUTER JOIN t_cp_pp_custom custom
   ON basdat.pre_processing_id = custom.pre_processing_id
   AND custom.partition_key_pre = '111100361A0700'
   AND basdat.customer_unique_id_f = custom.customer_unique_id_f
LEFT OUTER JOIN t_cp_pp_groups groups
  ON custom.partition_key_pre = '111100361A0700'
  AND basdat.pre_processing_id = groups.pre_processing_id
  AND custom.customer_group_id = groups.customer_group_id
WHERE basdat.partition_key_pre = '111100361A0700'; Did you consider to add subpartions to your tables? You could profit from some partition wise joins. Customer_Unique_ID would be a candidate for a hash subpartition.