Re: [HACKERS] What about LIMIT in SELECT ?

Jan Wieck wrote:

> And I got the time to hack around about this.
>
<...
a lovely explanation of a patch to achiev 60X speedup
for a typical web query
...>

> The speedup for the cursor/fetch scenario is so impressive
> that I'll create a post 6.4 patch. I don't want it in 6.4
> because there is absolutely no query in the whole regression
> test, where it suppresses the sort node.

Good, then it works as expected ;)

More seriously, it is not within powers of current regression test
framework to test speed improvements (only the case where
performance-wise bad implementation will actually crash the backend,
as in the cnfify problem, but AFAIK we dont test for those now)

> So we have absolutely no check that it doesn't break anything.

If it did pass the regression, then IMHO it did not break anything.

I would vote for putting it in (maybe with a
'set fix_optimiser_stupidity on' safeguard to enable it). I see no
reason to postpone it to 6.4.1 and force almost everybody to first
patch their copy and then upgrade very soon.

I would even go far enough to call it a bugfix, as it does not really
introduce any new functionality only fixes some existing functionality
so that much bigger databases can be actually used.

I would compare it in this sense to finding the places where
username/password get truncated below their actual values in pg_passwd
;)

---------------
Hannu Krosing