Re: Allow GiST opcalsses without compress\decompres functions

From: Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Andrey Borodin <x4mmm(at)yandex-team(dot)ru>, Dmitriy Sarafannikov <dsarafannikov(at)yandex(dot)ru>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Allow GiST opcalsses without compress\decompres functions
Date: 2017-09-20 14:09:38
Message-ID: CAPpHfdu7YRDT7pVOp8t-cpjqeO7RtqRdsU40kywOn7v-BvaGFQ@mail.gmail.com
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On Wed, Sep 20, 2017 at 5:02 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:

> Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru> writes:
> > On Wed, Sep 20, 2017 at 4:25 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> >> Yes. We don't allow out-of-line values, but we do allow compressed and
> >> short-header values.
>
> > BTW, this comment looks still invalid for me...
>
> >> #define SIGLENINT 4 /* >122 => key will *toast*, so very slow!!! */
>
> I haven't done the math to see if 122 is exactly the right value,
> but at some point index_form_tuple would decide that the tuple was
> uncomfortably big and try to compress it. So the comment is right
> in general terms.
>

If comment means toast as compression, not out-of-line storage then it's
true.
However, it would be good to rephrase this comment to clarify that.

------
Alexander Korotkov
Postgres Professional: http://www.postgrespro.com
The Russian Postgres Company

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