| From: | Andres Freund <andres(at)anarazel(dot)de> |
|---|---|
| To: | Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com> |
| Cc: | Peter Geoghegan <pg(at)bowt(dot)ie>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Robert Haas <robertmhaas(at)gmail(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | Re: POC: converting Lists into arrays |
| Date: | 2019-02-25 21:43:24 |
| Message-ID: | 20190225214324.ixn4r7rjoudmoylc@alap3.anarazel.de |
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| Lists: | pgsql-hackers |
Hi,
On 2019-02-25 22:35:37 +0100, Tomas Vondra wrote:
> So let's say we want to measure the improvement this patch gives us.
> What would be some reasonable (and corner) cases to benchmark? I do have
> some ideas, but as you've been looking at this in the past, perhaps you
> have something better.
I think queries over tables with a fair number of columns very easily
stress test the list overhead around targetlists - I don't have a
profile lying around, but the overhead of targetlist processing
(ExecTypeFromTL etc) at execution time clearly shows up. Larger
individual expressions can easily show up via eval_const_expressions()
etc and ExecInitExpr(). Both probably can be separated into benchmarks
with prepared statements (ExecTypeFromTl() and ExecInitExpr() will show
up, but planner work obviously not), and non-prepared benchmarks will
stress the planner more. I suspect there's also a few planner benefits
with large numbers of paths, but I don't quite remember the profiles
well enough to construct a benchmark from memory.
Greetings,
Andres Freund
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