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

PG Bug reporting form <noreply(at)postgresql(dot)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