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From: "David G. Johnston" <david.g.johnston@gmail.com>
Date: Tue, 30 Apr 2024 12:13:52 -0700
Message-ID: <CAKFQuwY4xifDbf8EZKwYtrECQiCbYsK_RLo+vnnWN-MuSSaqLQ@mail.gmail.com>
Subject: Re: Introduction of a new field in pg_class indicating presence of a
 large object in a table
To: Gaurav Pant <gauravpant145@gmail.com>
Cc: pgsql-general@lists.postgresql.org
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On Tue, Apr 30, 2024 at 11:57=E2=80=AFAM Gaurav Pant <gauravpant145@gmail.c=
om>
wrote:

> I wanted to know if there is any such system table that we can use to
> identify and map the fields containing large objects and the respective
> tables and if it is not already there, do we have any plans to incorporat=
e
> the same in pg_class like we have for pg_toast?
>
>
https://www.postgresql.org/docs/current/catalog-pg-largeobject.html

Large Objects are nothing like TOAST.  There is no system level association
between large objects and tables.  Sure, the DBA can choose to store a
large object OID in a table, but how you'd go about figuring out which
columns contain those is going to be installation specific.  Though
hopefully they used a bigint data type and maybe added "oid" to the column
name...I suppose it would be interesting if one could define a FK on a
table and point it at pg_largeobject_metadata but that I suspect would be
the extent to which we'd do something along the lines of your request.

David J.

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<div dir=3D"ltr"><div dir=3D"ltr"><div class=3D"gmail_default" style=3D"fon=
t-family:arial,helvetica,sans-serif"><span style=3D"font-family:Arial,Helve=
tica,sans-serif">On Tue, Apr 30, 2024 at 11:57=E2=80=AFAM Gaurav Pant &lt;<=
a href=3D"mailto:gauravpant145@gmail.com">gauravpant145@gmail.com</a>&gt; w=
rote:</span><br></div></div><div class=3D"gmail_quote"><blockquote class=3D=
"gmail_quote" style=3D"margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(2=
04,204,204);padding-left:1ex"><div dir=3D"ltr"><div>I wanted to know if the=
re is any such system table that we can use to identify and map the fields =
containing large objects and the respective tables and if it is not already=
 there, do we have any plans to incorporate the same in pg_class like we ha=
ve for pg_toast?<br></div><div><br></div></div></blockquote><div><br></div>=
<div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-seri=
f"><a href=3D"https://www.postgresql.org/docs/current/catalog-pg-largeobjec=
t.html">https://www.postgresql.org/docs/current/catalog-pg-largeobject.html=
</a></div><div class=3D"gmail_default" style=3D"font-family:arial,helvetica=
,sans-serif"><br></div><div class=3D"gmail_default" style=3D"font-family:ar=
ial,helvetica,sans-serif">Large Objects are nothing like TOAST.=C2=A0 There=
 is no system level association between large objects and tables.=C2=A0 Sur=
e, the DBA can choose to store a large object OID in a table, but how you&#=
39;d go about figuring out which columns contain those is going to be insta=
llation specific.=C2=A0 Though hopefully they used a bigint data type=C2=A0=
and maybe added &quot;oid&quot; to the column name...I suppose it would be =
interesting if one could define a FK on a table and point it at pg_largeobj=
ect_metadata but that I suspect would be the extent to which we&#39;d do so=
mething along the lines of your request.</div><div class=3D"gmail_default" =
style=3D"font-family:arial,helvetica,sans-serif"><br></div><div class=3D"gm=
ail_default" style=3D"font-family:arial,helvetica,sans-serif">David J.</div=
><div class=3D"gmail_default" style=3D"font-family:arial,helvetica,sans-ser=
if"><br></div></div></div>

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