Re: [HACKERS] MAIN, Uncompressed?

On 26 August 2017 at 05:40, Mark Kirkwood <mark.kirkwood@catalyst.net.nz> wrote:
> On 26/08/17 12:18, Simon Riggs wrote:
>
>> On 25 August 2017 at 20:53, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>>>
>>> Greg Stark <stark@mit.edu> writes:
>>>>
>>>> I think this is a particularly old piece of code and we're lucky the
>>>> default heuristics have served well for all this time because I doubt
>>>> many people fiddle with these storage attributes. The time may have
>>>> come to come up with a better UI for the storage attributes because
>>>> people are doing new things (like json) and wanting more control over
>>>> this heuristic.
>>>
>>> Yeah, I could get behind a basic rethinking of the tuptoaster control
>>> knobs.  I'm just not in love with Simon's specific proposal, especially
>>> not if we can't think of a better name for it than "MAINU".
>>
>> Extended/External would be just fine if you could set the toast
>> target, so I think a better suggestion would be to make "toast_target"
>> a per-attribute option .
>>
>
> +1, have thought about this myself previously....thank you for bringing it
> up!

OK, so table-level option for "toast_tuple_target", not attribute-level option

The attached patch and test shows this concept is useful and doesn't
affect existing data.

For 4x 4000 byte rows:
* by default we use 1 heap block and 3 toast blocks
* toast_tuple_target=4080 uses 2 heap blocks and 0 toast blocks

-- 
Simon Riggs                http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services

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