Re: pg_column_toast_chunk_id: a function to get a chunk ID of a TOASTed value

On Fri, Jan 26, 2024 at 8:42 AM Yugo NAGATA <nagata@sraoss.co.jp> wrote:
>
> On Tue, 2 Jan 2024 08:00:00 +0800
> jian he <jian.universality@gmail.com> wrote:
>
> > On Mon, Nov 6, 2023 at 8:00 AM jian he <jian.universality@gmail.com> wrote:
> > >
> > > minor doc issues.
> > > Returns the chunk id of the TOASTed value, or NULL if the value is not TOASTed.
> > > Should it be "chunk_id"?
>
> Thank you for your suggestion. As you pointed out, it is called "chunk_id"
> in the documentation, so I rewrote it and also added a link to the section
> where the TOAST table structure is explained.
>
> > > you may place it after pg_create_logical_replication_slot entry to
> > > make it look like alphabetical order.
>
> I've been thinking about where we should place the function in the doc,
> and I decided place it in the table  of Database Object Size Functions
> because I think pg_column_toast_chunk_id also would assist understanding
> the result of size functions as similar to pg_column_compression; that is,
> those function can explain why a large value in size could be stored in
> a column.

diff --git a/doc/src/sgml/func.sgml b/doc/src/sgml/func.sgml
index 210c7c0b02..2d82331323 100644
--- a/doc/src/sgml/func.sgml
+++ b/doc/src/sgml/func.sgml
@@ -28078,6 +28078,23 @@ postgres=# SELECT '0/0'::pg_lsn +
pd.segment_number * ps.setting::int + :offset
        </para></entry>
       </row>

+      <row>
+       <entry role="func_table_entry"><para role="func_signature">
+        <indexterm>
+         <primary>pg_column_toast_chunk_id</primary>
+        </indexterm>
+        <function>pg_column_toast_chunk_id</function> ( <type>"any"</type> )
+        <returnvalue>oid</returnvalue>
+       </para>
+       <para>
+        Shows the <structfield>chunk_id</structfield> of an on-disk
+        <acronym>TOAST</acronym>ed value. Returns <literal>NULL</literal>
+        if the value is un-<acronym>TOAST</acronym>ed or not on-disk.
+        See <xref linkend="storage-toast-ondisk"/> for details about
+        <acronym>TOAST</acronym>.
+       </para></entry>
+      </row>

v3 patch will place it on `Table 9.97. Replication Management Functions`
I agree with you. it should be placed after pg_column_compression. but
apply your patch, it will be at


> > > There is no test. maybe we can add following to src/test/regress/sql/misc.sql
> > > create table val(t text);
> > > INSERT into val(t) SELECT string_agg(
> > >   chr((ascii('B') + round(random() * 25)) :: integer),'')
> > > FROM generate_series(1,2500);
> > > select pg_column_toast_chunk_id(t) is  not null from val;
> > > drop table val;
>
> Thank you for the test proposal. However, if we add a test, I want
> to check that the chunk_id returned by the function exists in the
> TOAST table, and that it returns NULL if the values is not TOASTed.
> For the purpose, I wrote a test using a dynamic SQL since the table
> name of the TOAST table have to be generated from the main table's OID.
>
> > Hi
> > the main C function (pg_column_toast_chunk_id)  I didn't change.
> > I added tests as mentioned above.
> > tests put it on src/test/regress/sql/misc.sql, i hope that's fine.
> > I placed pg_column_toast_chunk_id in "Table 9.99. Database Object
> > Location Functions" (below Table 9.98. Database Object Size
> > Functions).
>
> I could not find any change in your patch from my previous patch.
> Maybe, you attached wrong file. I attached a patch updated based
> on your review, including the documentation fixes and a test.
> What do you think about this it?
>

sorry, I had attached the wrong file.
but your v3 also has no tests, documentation didn't fix.
maybe you also attached the wrong file too?