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Re: Pluggable toaster - Mailing list pgsql-hackers

From Nikita Malakhov
Subject Re: Pluggable toaster
Date
Msg-id CAN-LCVORMn85jAL4GCWpQf+H+eZ3vFoO2r+tOEn7k47uw2A9gg@mail.gmail.com
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In response to Re: Pluggable toaster  (Teodor Sigaev <teodor@sigaev.ru>)
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Hi Hackers,

In addition to original patch set for Pluggable Toaster, we have two more patches 
(actually, small, but important fixes), authored by Nikita Glukhov:

1) 0001-Fix-toast_tuple_externalize.patch
This patch fixes freeing memory in case of new toasted value is the same as old one, 
this seems incorrect, and in this case the function just returns instead of freeing old value;

2) 0002-Fix-alignment-of-custom-TOAST-pointers.patch
This patch adds data alignment for new varatt_custom data structure in building tuples, 
since varatt_custom must be aligned for custom toasters (in particular, this fix is very 
important to JSONb Toaster).

These patches must be applied on top of the latter 4_bytea_appendable_toaster_v1.patch.
Please consider them in reviewing Pluggable Toaster.

Regards.


On Wed, Feb 2, 2022 at 10:35 AM Teodor Sigaev <teodor@sigaev.ru> wrote:
> I agree ... but I'm also worried about what happens when we have
> multiple table AMs. One can imagine a new table AM that is
> specifically optimized for TOAST which can be used with an existing
> heap table. One can imagine a new table AM for the main table that
> wants to use something different for TOAST. So, I don't think it's
> right to imagine that the choice of TOASTer depends solely on the
> column data type. I'm not really sure how this should work exactly ...
> but it needs careful thought.

Right. that's why we propose a validate method  (may be, it's a wrong
name, but I don't known better one) which accepts several arguments, one
of which is table AM oid. If that method returns false then toaster
isn't useful with current TAM, storage or/and compression kinds, etc.

--
Teodor Sigaev                      E-mail: teodor@sigaev.ru
                                       WWW: http://www.sigaev.ru/



--
Nikita Malakhov
Postgres Professional 
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