Обсуждение: BUG #17806: PostgreSQL 13.10 returns "CREATE DATABASE cannot be executed within a pipeline"

The following bug has been logged on the website:

Bug reference:      17806
Logged by:          Wesley Smith
Email address:      wesley.smith@zapproved.com
PostgreSQL version: 13.10
Operating system:   Linux
Description:

I am starting up a fresh instance of Postgres inside of Docker using the
"postgres:13.10" tag.  I'm then connecting to the database server using the
Ppgsql library for .NET (version 6.0.8) and creating a new database like
this:

var str = "
  CREATE ROLE foo WITH PASSWORD 'foo' LOGIN NOINHERIT;
  GRANT foo TO postgres;
  CREATE DATABASE my_db OWNER foo;
  -- More statements here
";
conn = new NpgsqlConnection(connString);
var cmd = new NpgsqlCommand(sql, conn);
await cmd.ExecuteNonQueryAsync();


In all versions of PostgreSQL 13 before 10 (13.1 - 13.9), this works fine.
There is no error and the database is created as expected.
However, with version 13.10, I get this error:

Severity: ERROR
  InvariantSeverity: ERROR
  SqlState: 25001
  MessageText: CREATE DATABASE cannot be executed within a pipeline
  File: xact.c
  Line: 3412
  Routine: PreventInTransactionBlock


As far as I know, I'm not executing these statements in a pipeline or a
transaction.

I don't see anything in the 13.10 release notes that mentions anything about
this.  Please let me know whether 13.10 has a bug, or if it is correctly
enforcing something that should have always been enforced.

PG Bug reporting form <noreply@postgresql.org> writes:
> I am starting up a fresh instance of Postgres inside of Docker using the
> "postgres:13.10" tag.  I'm then connecting to the database server using the
> Ppgsql library for .NET (version 6.0.8) and creating a new database like
> this:

> var str = "
>   CREATE ROLE foo WITH PASSWORD 'foo' LOGIN NOINHERIT;
>   GRANT foo TO postgres;
>   CREATE DATABASE my_db OWNER foo;
>   -- More statements here
> ";
> conn = new NpgsqlConnection(connString);
> var cmd = new NpgsqlCommand(sql, conn);
> await cmd.ExecuteNonQueryAsync();

You'd have to ask the Ppgsql authors exactly how they transmit that
to the server; but a plausible guess is that it's using what we
refer to as a pipeline, that is a series of commands transmitted
without waiting for the result of earlier commands.

> In all versions of PostgreSQL 13 before 10 (13.1 - 13.9), this works fine. 
> There is no error and the database is created as expected.
> However, with version 13.10, I get this error:

> Severity: ERROR
>   InvariantSeverity: ERROR
>   SqlState: 25001
>   MessageText: CREATE DATABASE cannot be executed within a pipeline
>   File: xact.c
>   Line: 3412
>   Routine: PreventInTransactionBlock

It is intended that we disallow CREATE DATABASE within a pipeline,
and has been since 13.8 et al; but we fixed some bugs in that
prohibition in 13.10.  Looking at the release-note entry about it,
that only mentions ANALYZE, which is probably my own oversight.

The motivation was to prevent semantic anomalies if one command
in the pipeline fails --- previously, you might end up with a
surprising subset of the commands having gotten committed.

            regards, tom lane

On Fri, Feb 24, 2023 at 7:56 AM Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> It is intended that we disallow CREATE DATABASE within a pipeline,
> and has been since 13.8 et al; but we fixed some bugs in that
> prohibition in 13.10.  Looking at the release-note entry about it,
> that only mentions ANALYZE, which is probably my own oversight.
>

Tom,

Thanks for the clarification that this is expected behavior.  I'll
update my code to put the "CREATE DATABASE" line in a separate call.

-- Wesley Smith