Re: Compression of full-page-writes

On 9 December 2014 at 04:09, 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.

Yes, I think USERSET would work fine for this.

>> * ideally we'd like to be able to differentiate the types of usage.
>> which then allows the user to control the level of compression
>> depending upon the type of action. My first cut at what those settings
>> should be are ALL > LOGICAL > PHYSICAL > VACUUM.
>>
>> VACUUM - only compress while running vacuum commands
>> PHYSICAL - only compress while running physical DDL commands (ALTER
>> TABLE set tablespace, CREATE INDEX), i.e. those that wouldn't
>> typically be used for logical decoding
>> LOGICAL - compress FPIs for record types that change tables
>> ALL - all user commands
>> (each level includes all prior levels)
>
> Interesting idea, but what evidence do we have that a simple on/off
> switch isn't good enough?

Yes, I think that was overcooked. What I'm thinking is that in the
long run we might have groups of parameters attached to different
types of action, so we wouldn't need, for example, two parameters for
work_mem and maintenance_work_mem. We'd just have work_mem and then a
scheme that has different values of work_mem for different action
types.

--
Simon Riggs http://www.2ndQuadrant.com/
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