a fixing patch, as the patch is incorrect. Instead, I
> just want to show disabling the simplify_function() function brings
> performance benefit, and it seems unexpected. I am wondering whether we can
> optimize simplify_function() to make the performance better for this
> workload?
>
>
>
> Environment:
> I used 1 GB data of TPC-H benchmark, and my entire data folder can be
> downloaded here:
> https://drive.google.com/file/d/1ZBLHanIRwxbaMQIhRUSPv4I7y8g_0AWi/view?usp=sharing
> The connection string is: postgresql://ubuntu:ubuntu@127.0.0.1:5432/tpch"
>
> tpch=# select version();
> version
>
>
> --
> PostgreSQL 17.0 on x86_64-pc-linux-gnu, compiled by gcc (Ubuntu
> 13.2.0-23ubuntu4) 13.2.0, 64-bit
> (1 row)
>
>
> Best regards,
>
> Jinsheng Ba
>
>
> Notice: This email is generated from the account of an NUS alumnus.
> Contents, views, and opinions therein are solely those of the sender.
>
--
*Best Regards *
*Shiv Iyer *
ap Index Scan on idx_test (cost=0.00..4.20 rows=6 width=0)
> (actual time=4425.432..4425.432 rows=0 loops=1)
> Index Cond: ((test.value)::text = '<<<<<<<<<<<<<<<<<<<<<<<<<<<<
> ... a lot symbols ...<<<<<<<<<<<<<<<<<<<<<<<<<<'::text)
> Buffers: shared hit=1
> Planning Time: 1.082 ms
> Execution Time: 4425.602 ms
> (9 rows)
>
> Time: 4433.001 ms (00:04.433)
>
> Observations*:*
>
>- The performance degradation occurs with certain special characters
>like < , !, >, @ , #, ... .
>- Queries using alphabetic characters or appending/prepending
>characters execute much faster.
>- The execution time increases exponentially with the length of the
>string composed of special characters.
>- Changing the collation to 'C' in the query significantly improves
>performance.
>
> Questions*:*
>
>
>- Is this performance degradation expected due to collation handling
>of certain special characters in PostgreSQL?
>- Are there any recommendations to improve performance without
>changing the column or database collation?
>
> --
> Best regards,
> Andrey Stikheev
>
--
*Best Regards *
*Shiv Iyer *
g Time: 0.095 ms
> Execution Time: 0.070 ms
>
> My question is, why isn't it using the index for column b? Is this expected?
> And why is it doing heap lookups for every row,.
>
> Performance is still good, but I am curious.
>
> Thanks in advance!
>
>
--
*Best Regards *
*Shiv Iyer *
Hi Burmokh,
Please take a look at this article copied below and ping me for further
guidance. Thanks!
How expensive SQLs can impact PostgreSQL Performance? -
https://minervadb.xyz/how-expensive-sqls-can-impact-postgresql-performance/
—
Best
Shiv
> On 30-Jan-2023, at 11:17 PM, Mok wrot
