Re: Data is copied twice when specifying both child and parent table in publication

Hi Wang-san. Here are my review comments for HEAD_v12-0001 patch.

======

1. Missing documentation.

In [1] you wrote:
> I think the behaviour of multiple publications with parameter publish_via_partition_root could be added to the pg-doc
laterin a separate patch. 

~

That doesn't seem right to me. IMO the related documentation updates
cannot really be separated from this patch. Otherwise, what's the
alternative? Push this change, and then (while waiting for the
documentation patch) users will just have to use trial and error to
guess how it works...?

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2. src/backend/catalog/pg_publication.c

+ typedef struct
+ {
+ Oid relid; /* OID of published table */
+ Oid pubid; /* OID of publication that publishes this
+ * table. */
+ } published_rel;

2a.
I think that should be added to typedefs.list

~

2b.
Maybe this also needs some comment to clarify that there will be
*multiple* of these structures in scenarios where the same table is
published by different publications in the array passed.

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3. QUESTION - pg_get_publication_tables / fetch_table_list

When the same table is published by different publications (but there
are other differences like row-filters/column-lists in each
publication) the result tuple of this function does not include the
pubid. Maybe the SQL of pg_publication_tables/fetch_table_list() is OK
as-is but how does it manage to associate each table with the correct
tuple?

I know it apparently all seems to work but I’m not how does that
happen? Can you explain why a puboid is not needed for the result
tuple of this function?

~~

test_pub=# create table t1(a int, b int, c int);
CREATE TABLE
test_pub=# create publication pub1 for table t1(a) where (a > 99);
CREATE PUBLICATION
test_pub=# create publication pub2 for table t1(a,b) where (b < 33);
CREATE PUBLICATION

Following seems OK when I swap orders of publication names...

test_pub=# SELECT gpt.relid, gpt.attrs, pg_get_expr(gpt.qual,
gpt.relid) AS rowfilter from pg_get_publication_tables(VARIADIC
ARRAY['pub2','pub1']) gpt(relid, attrs, qual);
 relid | attrs | rowfilter
-------+-------+-----------
 16385 | 1 2   | (b < 33)
 16385 | 1     | (a > 99)
(2 rows)

test_pub=# SELECT gpt.relid, gpt.attrs, pg_get_expr(gpt.qual,
gpt.relid) AS rowfilter from pg_get_publication_tables(VARIADIC
ARRAY['pub1','pub2']) gpt(relid, attrs, qual);
 relid | attrs | rowfilter
-------+-------+-----------
 16385 | 1     | (a > 99)
 16385 | 1 2   | (b < 33)
(2 rows)

But what about this (this is similar to the SQL fragment from
fetch_table_list); I swapped the pub names but the results are the
same...

test_pub=# SELECT pg_get_publication_tables(VARIADIC
array_agg(p.pubname)) from pg_publication p where pubname
IN('pub2','pub1');

                     pg_get_publication_tables


----------------------------------------------------------------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------
 (16385,1,"{OPEXPR :opno 521 :opfuncid 147 :opresulttype 16 :opretset
false :opcollid 0 :inputcollid 0 :args ({VAR :varno 1 :varattno 1
:vartype 23 :vartypmod -1 :var
collid 0 :varlevelsup 0 :varnosyn 1 :varattnosyn 1 :location 47}
{CONST :consttype 23 :consttypmod -1 :constcollid 0 :constlen 4
:constbyval true :constisnull false :
location 51 :constvalue 4 [ 99 0 0 0 0 0 0 0 ]}) :location 49}")
 (16385,"1 2","{OPEXPR :opno 97 :opfuncid 66 :opresulttype 16
:opretset false :opcollid 0 :inputcollid 0 :args ({VAR :varno 1
:varattno 2 :vartype 23 :vartypmod -1 :v
arcollid 0 :varlevelsup 0 :varnosyn 1 :varattnosyn 2 :location 49}
{CONST :consttype 23 :consttypmod -1 :constcollid 0 :constlen 4
:constbyval true :constisnull false
 :location 53 :constvalue 4 [ 33 0 0 0 0 0 0 0 ]}) :location 51}")
(2 rows)

test_pub=# SELECT pg_get_publication_tables(VARIADIC
array_agg(p.pubname)) from pg_publication p where pubname
IN('pub1','pub2');

                     pg_get_publication_tables


----------------------------------------------------------------------------------------------------------------------------------------------------------------------

----------------------------------------------------------------------------------------------------------------------------------------------------------------------
-------------------------------------------------------------------
 (16385,1,"{OPEXPR :opno 521 :opfuncid 147 :opresulttype 16 :opretset
false :opcollid 0 :inputcollid 0 :args ({VAR :varno 1 :varattno 1
:vartype 23 :vartypmod -1 :var
collid 0 :varlevelsup 0 :varnosyn 1 :varattnosyn 1 :location 47}
{CONST :consttype 23 :consttypmod -1 :constcollid 0 :constlen 4
:constbyval true :constisnull false :
location 51 :constvalue 4 [ 99 0 0 0 0 0 0 0 ]}) :location 49}")
 (16385,"1 2","{OPEXPR :opno 97 :opfuncid 66 :opresulttype 16
:opretset false :opcollid 0 :inputcollid 0 :args ({VAR :varno 1
:varattno 2 :vartype 23 :vartypmod -1 :v
arcollid 0 :varlevelsup 0 :varnosyn 1 :varattnosyn 2 :location 49}
{CONST :consttype 23 :consttypmod -1 :constcollid 0 :constlen 4
:constbyval true :constisnull false
 :location 53 :constvalue 4 [ 33 0 0 0 0 0 0 0 ]}) :location 51}")
(2 rows)


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[1]
https://www.postgresql.org/message-id/OS3PR01MB6275A9B8C65C381C6828DF9D9E549%40OS3PR01MB6275.jpnprd01.prod.outlook.com

Kind Regards,
Peter Smith.
Fujitsu Australia