Re: Compression of full-page-writes

On Thu, Dec 11, 2014 at 10:33 PM, Michael Paquier
<michael(dot)paquier(at)gmail(dot)com> wrote:
> On Tue, Dec 9, 2014 at 4:09 AM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> On Sun, Dec 7, 2014 at 9:30 PM, Simon Riggs <simon(at)2ndquadrant(dot)com> wrote:
>> > * parameter should be SUSET - it doesn't *need* to be set only at
>> > server start since all records are independent of each other
>>
>> Why not USERSET? There's no point in trying to prohibit users from
>> doing things that will cause bad performance because they can do that
>> anyway.
>
> Using SUSET or USERSET has a small memory cost: we should
> unconditionally palloc the buffers containing the compressed data
> until WAL is written out. We could always call an equivalent of
> InitXLogInsert when this parameter is updated but that would be
> bug-prone IMO and it does not plead in favor of code simplicity.

I don't understand what you're saying here.

--
Robert Haas
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