Re: Support logical replication of DDLs

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)