Parallel Hint Ignored With Large Number Of Columns In Select List
(Doc ID 1267953.1)
Last updated on NOVEMBER 07, 2023
Applies to:
Oracle Database - Enterprise Edition - Version 10.2.0.1 to 10.2.0.4 [Release 10.2]Oracle Database Cloud Schema Service - Version N/A and later
Oracle Database Exadata Cloud Machine - Version N/A and later
Oracle Cloud Infrastructure - Database Service - Version N/A and later
Oracle Database Backup Service - Version N/A and later
Information in this document applies to any platform.
Reviewed 11-Dec-2014.
Symptoms
The parallel hint ignores with large numbers of columns in select list, for example:
select /*+ parallel ("DUAL",4) */
1,2,3,4,5,6,7,8,9,0,
1,2,3,4,5,6,7,8,9,0,
[...]
[...] <--- Y same row
from dual
where dummy='X'
union
select /*+ parallel ("DUAL",4) */
1,2,3,4,5,6,7,8,9,0,
1,2,3,4,5,6,7,8,9,0,
[...]
[...] <--- Y same row
from dual
where dummy='X'
/
with Y=1000 it works
with Y=2000 it does not use parallelism
Basically, using about 2000 rows, then the parallelism doesn't work.
Using 1000 rows:
Cause
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In this Document
| Symptoms |
| Cause |
| Solution |
| References |