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

From: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>
To: Jeff Janes <jeff(dot)janes(at)gmail(dot)com>
Cc: Dilip kumar <dilip(dot)kumar(at)huawei(dot)com>, Sawada Masahiko <sawada(dot)mshk(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>, Jan Lentfer <Jan(dot)Lentfer(at)web(dot)de>, Euler Taveira <euler(at)timbira(dot)com(dot)br>
Subject: Re: TODO : Allow parallel cores to be used by vacuumdb [ WIP ]
Date: 2014-06-30 22:17:37
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Jeff Janes wrote:

> 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.)

I think commit d2c1740dc275543a46721ed254ba3623f63d2204 is apropos.
Maybe we should move pgpipe back to src/port and have pg_dump and this
new thing use that. I'm not sure about the rest of duplication in
vac_parallel.c; there might be a lot in common with what
pg_dump/parallel.c does too. Having two copies of code is frowned upon
for good reasons. This patch introduces 1200 lines of new code in
vac_parallel.c, ugh.

If we really require 1200 lines to get parallel vacuum working for
vacuumdb, I would question the wisdom of this effort. To me, it seems
better spent improving autovacuum to cover whatever it is that this
patch is supposed to be good for --- or maybe just enable having a shell
script that launches multiple vacuumdb instances in parallel ...

Álvaro Herrera
PostgreSQL Development, 24x7 Support, Training & Services

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