Re: Online enabling of checksums

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От Magnus Hagander
Тема Re: Online enabling of checksums
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Msg-id CABUevEyRsAUOTVqQ8PvCAOHd+0foKTwRq34QD3LuGVLa0ydHLg@mail.gmail.com
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Ответ на Re: Online enabling of checksums  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
Ответы Re: Online enabling of checksums  (Tomas Vondra <tomas.vondra@2ndquadrant.com>)
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On Mon, Mar 26, 2018 at 10:09 PM, Tomas Vondra <tomas.vondra@2ndquadrant.com> wrote:
Hi,

I see enable_data_checksums() does this:

    if (cost_limit <= 0)
        ereport(ERROR,
                (errmsg("cost limit must be a positive value")));

Is there a reason not to allow -1 (no limit), just like for vacuum_cost?


Eh. vaccum_cost_limit cannot be set to -1 (1 is the lowest). Neither can vacuum_cost_delay -- it is set to *0* to disable it (which is how the cost_delay parameter is handled here as well).

Are you thinking autovacuum_vacuum_cost_limit where -1 means "use vacuum_cost_limit"?

The reason to disallow cost_limit=0 is to avoid divide-by-zero. We could allow -1 and have it mean "use vacuum_cost_limit", but I'm not sure how relevant that really would be in this context?

--

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