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

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От Jeff Janes
Тема Re: TODO : Allow parallel cores to be used by vacuumdb [ WIP ]
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Msg-id CAMkU=1xdbaw7RSPS1pWhwj7WUiRoh+HNAhV3d2a5zuJjQo3ovQ@mail.gmail.com
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Ответ на Re: TODO : Allow parallel cores to be used by vacuumdb [ WIP ]  (Alvaro Herrera <alvherre@2ndquadrant.com>)
Ответы Re: TODO : Allow parallel cores to be used by vacuumdb [ WIP ]  (Simon Riggs <simon@2ndQuadrant.com>)
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On Fri, Sep 26, 2014 at 11:47 AM, Alvaro Herrera <alvherre@2ndquadrant.com> wrote:
Gavin Flower wrote:

> Curious: would it be both feasible and useful to have multiple
> workers process a 'large' table, without complicating things too
> much?  The could each start at a different position in the file.

Feasible: no.  Useful: maybe, we don't really know.  (You could just as
well have a worker at double the speed, i.e. double vacuum_cost_limit).

Vacuum_cost_delay is already 0 by default.  So unless you changed that, vacuum_cost_limit does not take effect under vacuumdb.

It is pretty easy for vacuum to be CPU limited, and even easier for analyze to be CPU limited (It does a lot of sorting).  I think analyzing is the main use case for this patch, to shorten the pg_upgrade window.  At least, that is how I anticipate using it.

Cheers,

Jeff

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