Re: TODO : Allow parallel cores to be used by vacuumdb [ WIP ]

On Fri, Jun 27, 2014 at 4:10 AM, Dilip kumar <dilip(dot)kumar(at)huawei(dot)com> wrote:
...
>
> Updated patch is attached in the mail..

Thanks Dilip.

I get a compiler warning when building on Windows. When I started
looking into that, I see that two files have too much code duplication
between them:

src/bin/scripts/vac_parallel.c (new file)
src/bin/pg_dump/parallel.c (existing file)

In particular, pgpipe is almost an exact duplicate between them,
except the copy in vac_parallel.c has fallen behind changes made to
parallel.c. (Those changes would have fixed the Windows warnings). I
think that this function (and perhaps other parts as
well--"exit_horribly" for example) need to refactored into a common
file that both files can include. I don't know where the best place
for that would be, though. (I haven't done this type of refactoring
myself.)

Also, there are several places in the patch which use spaces for
indentation where tabs are called for by the coding style. It looks
like you may have copied the code from one terminal window and copied
it into another one, converting tabs to spaces in the process. This
makes it hard to evaluate the amount of code duplication.

In some places the code spins in a tight loop while waiting for a
worker process to become free. If I strace the process, I got a long
list of selects with 0 time outs:

select(13, [6 8 10 12], NULL, NULL, {0, 0}) = 0 (Timeout)

I have not tried to track down the code that causes it. I did notice
that vacuumdb spends an awful lot of time at the top of the Linux
"top" output, and this is probably why.

Cheers,

Jeff