Re: Seq scans status update - Mailing list pgsql-patches

CK Tan wrote:
> If it is convenient for you, could you run my patch against the same
> hardware and data to get some numbers on select for comparison? Although
> we don't address updates, copy, or inserts,  we are definitely getting
> at least 20% improvement in scans here without poisoning the bufpool for
> large tables.

Sure, here you are:

  copy-cktan-big                    | 00:10:08.843126
  copy-cktan-big                    | 00:10:17.767606
  copy-cktan-big                    | 00:09:37.797059
  copy_nowal-cktan-big              | 00:05:12.305025
  copy_nowal-cktan-big              | 00:05:10.518417
  copy_nowal-cktan-big              | 00:05:03.472939
  select-cktan-big                  | 00:03:27.655982
  select-cktan-big                  | 00:01:55.496408
  select-cktan-big                  | 00:01:31.693856
  select-cktan-big                  | 00:01:12.705268
  select-cktan-big                  | 00:01:12.478247
  select-cktan-big                  | 00:01:10.866484
  vacuum_clean-cktan-big            | 00:03:05.340875
  vacuum_clean-cktan-big            | 00:01:12.428317
  vacuum_clean-cktan-big            | 00:01:13.179957
  vacuum_clean-cktan-big            | 00:01:10.438888
  vacuum_hintbits-cktan-big         | 00:03:58.78208
  vacuum_hintbits-cktan-big         | 00:04:02.515778
  vacuum_hintbits-cktan-big         | 00:04:19.083402
  vacuum_hintbits-cktan-big         | 00:04:11.170831
  copy-cktan-med                    | 00:02:19.413484
  copy-cktan-med                    | 00:02:22.270497
  copy-cktan-med                    | 00:02:22.297946
  copy_nowal-cktan-med              | 00:01:31.192601
  copy_nowal-cktan-med              | 00:01:17.736356
  copy_nowal-cktan-med              | 00:01:32.272778
  select-cktan-med                  | 00:00:03.774974
  select-cktan-med                  | 00:00:01.279276
  select-cktan-med                  | 00:00:01.297703
  select-cktan-med                  | 00:00:01.304129
  select-cktan-med                  | 00:00:01.297048
  select-cktan-med                  | 00:00:01.306073
  vacuum_clean-cktan-med            | 00:00:01.820733
  vacuum_clean-cktan-med            | 00:00:01.755684
  vacuum_clean-cktan-med            | 00:00:01.755659
  vacuum_clean-cktan-med            | 00:00:01.750972
  vacuum_hintbits-cktan-med         | 00:00:01.58744
  vacuum_hintbits-cktan-med         | 00:00:06.216038
  vacuum_hintbits-cktan-med         | 00:00:02.201789
  vacuum_hintbits-cktan-med         | 00:00:36.494427

Select performance looks the same as with Simon's/my patch.

That 20% gain must be hardware-dependent. My interpretation is that the
CPU savings from more efficient cache usage only matters when the I/O
bandwidth is high enough that CPU becomes the bottleneck.

--
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com