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From: Imseih (AWS), Sami <[email protected]>
To: Robert Haas <[email protected]>
To: Nathan Bossart <[email protected]>
Cc: Bertrand Drouvot <[email protected]>
Cc: [email protected] <[email protected]>
Subject: Re: Track the amount of time waiting due to cost_delay
Date: Tue, 11 Jun 2024 21:04:29 +0000
Message-ID: <[email protected]> (raw)
In-Reply-To: <CA+Tgmoatdfycby69ZvAQkwa9RbKUebzqTe4W4_Eh53RN08nK_Q@mail.gmail.com>
References: <[email protected]>
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	<CA+TgmoY6nAVESkFj527-K2HLELt3JK+QrO37udzDp9KQqoTZrQ@mail.gmail.com>
	<[email protected]>
	<CA+TgmoZiC=zeCDYuMpB+Gb2yK=rTQCGMu0VoxehocKyHxr9Erg@mail.gmail.com>
	<[email protected]>
	<ZmibwXuVL1iVH7pJ@nathan>
	<CA+Tgmoatdfycby69ZvAQkwa9RbKUebzqTe4W4_Eh53RN08nK_Q@mail.gmail.com>

>> I'm struggling to think of a scenario in which the number of waits would be
>> useful, assuming you already know the amount of time spent waiting. Even
>> if the number of waits is huge, it doesn't tell you much else AFAICT. I'd
>> be much more likely to adjust the cost settings based on the percentage of
>> time spent sleeping.


> This is also how I see it.

I think it may be useful for a user to be able to answer the "average
sleep time" for a vacuum, especially because the vacuum cost 
limit and delay can be adjusted on the fly for a running vacuum.

If we only show the total sleep time, the user could make wrong
 assumptions about how long each sleep took and they might 
assume that all sleep delays for a particular vacuum run have been 
uniform in duration, when in-fact they may not have been.


Regards,

Sami 

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