On Thu, Aug 27, 2020 at 8:04 AM Greg Nancarrow <
gregn4422@gmail.com> wrote:
> - Parallel Copy with 1 worker ran slower than normal Copy in a couple
> of cases (I did question if allowing 1 worker was useful in my patch
> review).
Thanks Greg for your review & testing.
I had executed various tests with 1GB, 2GB & 5GB with 100 columns without parallel mode & with 1 parallel worker. Test result for the same is as given below:
| Test | Without parallel mode | With 1 Parallel worker |
1GB csv file 100 columns
(100 bytes data in each column) | 62 seconds | 47 seconds (1.32X) |
1GB csv file 100 columns
(1000 bytes data in each column) | 89 seconds | 78 seconds (1.14X) |
2GB csv file 100 columns
(1 byte data in each column) | 277 seconds | 256 seconds (1.08X) |
5GB csv file 100 columns
(100 byte data in each column) | 515 seconds | 445 seconds (1.16X) |
I have run the tests multiple times and have noticed the similar execution times in all the runs for the above tests.
In the above results there is slight improvement with 1 worker. In my tests I did not observe the degradation for copy with 1 worker compared to the non parallel copy. Can you share with me the script you used to generate the data & the ddl of the table, so that it will help me check that scenario you faced the problem.