Re: parallel mode and parallel contexts

On 2014-12-22 14:14:31 -0500, Robert Haas wrote:
> On Fri, Dec 19, 2014 at 8:59 AM, Robert Haas <robertmhaas@gmail.com> wrote:
> > And here is a new version.
>
> Here is another new version, with lots of bugs fixed.

A couple remarks:
* Shouldn't this provide more infrastructure to deal with the fact that we might get less parallel workers than we had
plannedfor?
 
* I wonder if parallel contexts shouldn't be tracked via resowners
* combocid.c should error out in parallel mode, as insurance
* I doubt it's a good idea to allow heap_insert, heap_inplace_update, index_insert. I'm not convinced that those will
behandled correct and relaxing restrictions is easier than adding them.
 
* I'd much rather separate HandleParallelMessageInterrupt() in one variant that just tells the machinery there's a
interrupt(called from signal handlers) and one that actually handles them. We shouldn't even consider adding any new
codethat does allocations, errors and such in signal handlers. That's just a *bad* idea.
 
* I'm not a fan of the shm_toc stuff... Verbose and hard to read. I'd much rather place a struct there and be careful
aboutnot using pointers. That also would obliviate the need to reserve some ids.
 
* Doesn't the restriction in GetSerializableTransactionSnapshotInt() apply for repeatable read just the same?
* I'm not a fan of relying on GetComboCommandId() to restore things in the same order as before.
* I'd say go ahead and commit the BgworkerByOid thing earlier/independently. I've seen need for that a couple times.
* s/entrypints/entrypoints/

Greetings,

Andres Freund

-- Andres Freund                       http://www.2ndQuadrant.com/PostgreSQL Development, 24x7 Support, Training &
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