Feedback-ID: ia2694551:Fastmail
Date: Sun, 26 Jun 2022 19:50:27 +0200
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: vignesh C <vignesh21@gmail.com>
Cc: "houzj.fnst@fujitsu.com" <houzj.fnst@fujitsu.com>,
	Amit Kapila <amit.kapila16@gmail.com>,
	Masahiko Sawada <sawada.mshk@gmail.com>,
	Japin Li <japinli@hotmail.com>, Dilip Kumar <dilipbalaut@gmail.com>,
	rajesh singarapu <rajesh.rs0541@gmail.com>,
	PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>,
	Zheng Li <zhengli10@gmail.com>
Subject: Re: Support logical replication of DDLs
Message-ID: <20220626175027.7glhsnfwfbo2pyxt@alvherre.pgsql>
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On 2022-Jun-22, vignesh C wrote:

> 1) Creation of temporary table fails infinitely in the subscriber.
> CREATE TEMPORARY TABLE temp1 (a int primary key);
> 
> The above statement is converted to the below format:
> CREATE TEMPORARY TABLE  pg_temp.temp1 (a pg_catalog.int4   ,
> CONSTRAINT temp1_pkey PRIMARY KEY (a));
> While handling the creation of temporary table in the worker, the
> worker fails continuously with the following error:
> 2022-06-22 14:24:01.317 IST [240872] ERROR:  schema "pg_temp" does not exist

Perhaps one possible fix is to change the JSON format string used in
deparse_CreateStmt.  Currently, the following is used:

+       if (node->ofTypename)
+               fmtstr = "CREATE %{persistence}s TABLE %{if_not_exists}s %{identity}D "
+                       "OF %{of_type}T %{table_elements}s "
+                       "%{with_clause}s %{on_commit}s %{tablespace}s";
+       else
+               fmtstr = "CREATE %{persistence}s TABLE %{if_not_exists}s %{identity}D "
+                       "(%{table_elements:, }s) %{inherits}s "
+                       "%{with_clause}s %{on_commit}s %{tablespace}s";
+
+       createStmt =
+               new_objtree_VA(fmtstr, 1,
+                                          "persistence", ObjTypeString,
+                                          get_persistence_str(relation->rd_rel->relpersistence));

(Note that the word for the "persistence" element here comes straight
from relation->rd_rel->relpersistence.)  Maybe it would be more
appropriate to set the schema to empty when the table is temp, since the
temporary-ness is in the %{persistence} element, and thus there is no
need to schema-qualify the table name.


However, that would still replicate a command that involves a temporary
table, which perhaps should not be considered fit for replication.  So
another school of thought is that if the %{persistence} is set to
TEMPORARY, then it would be better to skip replicating the command
altogether.  I'm not sure how to plug that in the replication layer,
however.

-- 
Álvaro Herrera         PostgreSQL Developer  —  https://www.EnterpriseDB.com/
"At least to kernel hackers, who really are human, despite occasional
rumors to the contrary" (LWN.net)