Re: [HACKERS] MAIN, Uncompressed?

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От Tom Lane
Тема Re: [HACKERS] MAIN, Uncompressed?
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Msg-id 14901.1503666499@sss.pgh.pa.us
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Ответ на Re: [HACKERS] MAIN, Uncompressed?  (Simon Riggs <simon@2ndquadrant.com>)
Ответы Re: [HACKERS] MAIN, Uncompressed?  (Simon Riggs <simon@2ndquadrant.com>)
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Simon Riggs <simon@2ndquadrant.com> writes:
> On 25 August 2017 at 13:21, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> If you know compression isn't useful, but you don't want to fail on
>> wide values, then "external" should serve the purpose.

> Well, almost. External toasts at 2048-ish bytes whereas Main toasts at
> 8160 bytes.
> The rows are typically near 4kB long, so if marked External they would
> always be toasted.
> It's desirable to have the full row in the heap block, rather than
> have to access heap-toastindex-toastblocks in all cases.
> The data is also incompressible, so Main just wastes time on insert.
> Hence, we have a missing option.

Maybe, but the use case seems mighty narrow.
        regards, tom lane



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