Re: Doc limitation update proposal: include out-of-line OID usage per TOAST-ed columns

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От John Naylor
Тема Re: Doc limitation update proposal: include out-of-line OID usage per TOAST-ed columns
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Msg-id CAFBsxsEfD7iQNimgFdGf4xNMCmSE8acw4PEm+P78d51_ze6Tzg@mail.gmail.com
обсуждение исходный текст
Ответ на Re: Doc limitation update proposal: include out-of-line OID usage per TOAST-ed columns  (Jakub Wartak <jakub.wartak@enterprisedb.com>)
Ответы Re: Doc limitation update proposal: include out-of-line OID usage per TOAST-ed columns  ("Andrey M. Borodin" <x4mmm@yandex-team.ru>)
Список pgsql-hackers
On Wed, Jul 5, 2023 at 9:45 PM Jakub Wartak <jakub.wartak@enterprisedb.com> wrote:

> [v3]

--- a/doc/src/sgml/limits.sgml
+++ b/doc/src/sgml/limits.sgml
@@ -10,6 +10,7 @@
   hard limits are reached.
  </para>
 
+
  <table id="limits-table">

@@ -92,11 +93,25 @@
      <entry>can be increased by recompiling <productname>PostgreSQL</productname></entry>
     </row>
 
-   <row>
-    <entry>partition keys</entry>
-    <entry>32</entry>
-    <entry>can be increased by recompiling <productname>PostgreSQL</productname></entry>
-   </row>
+    <row>
+     <entry>partition keys</entry>
+     <entry>32</entry>
+     <entry>can be increased by recompiling <productname>PostgreSQL</productname></entry>
+    </row>

Ahem.

> > Also, perhaps the LO entries should be split into a separate patch. Since they are a special case and documented elsewhere, it's not clear their limits fit well here. Maybe they could.
>
> Well, but those are *limits* of the engine and they seem to be pretty widely chosen especially in migration scenarios (because they are the only ones allowed to store over 1GB). I think we should warn the dangers of using pg_largeobjects.  

I see no argument here against splitting into a separate patch for later.

> > Also the shared counter is the cause of the slowdown, but not the reason for the numeric limit.
>
> Isn't it both? typedef Oid is unsigned int = 2^32, and according to GetNewOidWithIndex() logic if we exhaust the whole OID space it will hang indefinitely which has the same semantics as "being impossible"/permanent hang (?)

Looking again, I'm thinking the OID type size is more relevant for the first paragraph, and the shared/global aspect is more relevant for the second.

The last issue is how to separate the notes at the bottom, since there are now two topics.

--
John Naylor
EDB: http://www.enterprisedb.com

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