Partition Name in Select and Group-By

Question

Is there a function that returns the partition name a row is stored in? I'd like to use it in a SELECT statement, if it exists.
The goal is to get row counts per partition to determine skew on a hash-based partition (otherwise, I'd just select and group-by the partition key). I want to do something like this:
SELECT PARTITION_NAME, COUNT(*) as PER_PART_COUNT
  FROM SOMETABLE
GROUP BY PARTITION_NAME;Obviously, I would replace the string "*PARTITION_NAME*" with whatever function returns that value.
NOTE: Before the forum sharks jump all over me, I did search the documentation and forums, but I came up empty handed.

Answer 1

Hi,
This is hokey - but you can use the undocumented function "tbl$or$idx$part$num" like so:
SELECT   atp.partition_name
       , COUNT (*) AS count_rows
    FROM all_tab_partitions atp
       , (SELECT tbl$or$idx$part$num ("SCOTT"."TAB1"
                                    , 0
                                    , 1
                                    , 0
                                    , partition_col1 -- your 1st partition key column
                                    , partition_col2 -- your 2nd partition key column
                                     ) AS part_num
               , 'TAB1' AS table_name
               , 'SCOTT' AS owner
            FROM scott.tab1) pt
   WHERE atp.table_name = pt.table_name
     AND atp.table_owner = pt.owner
     AND atp.partition_position = pt.part_num
GROUP BY atp.partition_name;Note - this probably won't perform well at all... but it could be an option...
Message was edited by:
PDaddy
... On 2nd thought - don't do it - it seems it is pretty unstable - brought my session to a halt a couple of times... Forget I mentioned it :)
... On 3rd thought - if you add ROWNUM - it works fine - seems you need to materialize the result set in the inner query - like so:
CREATE TABLE part_tab (part_key int
                     , a int
partition by range (part_key)
(partition p1 values less than (100)
,partition p2 values less than (200)
,partition p3 values less than (maxvalue)
insert into part_tab
select rownum
     , rownum
FROM all_objects
where rownum <= 1000; SELECT atp.partition_name
     , COUNT(*) AS count_rows
FROM all_tab_partitions atp
   , (SELECT TBL$OR$IDX$PART$NUM("PART_TAB", 0, 1, 0, part_key) AS part_num
           , 'PART_TAB' AS table_name
           , user AS owner
           , ROWNUM AS rn -- Materialize the result set by adding ROWNUM...
      FROM part_tab) pt
WHERE atp.table_name = pt.table_name
  AND atp.table_owner = pt.owner
  AND atp.partition_position = pt.part_num
GROUP BY atp.partition_name;