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