Re: Extensibility of the PostgreSQL wire protocol

On Thu, Feb 18, 2021 at 9:32 PM Jan Wieck <jan(at)wi3ck(dot)info> wrote:
>
And, here is how it looks with the following configuration:
telnet_srv.port = 1433
telnet_srv.listen_addresses = '*'

telnet localhost 1433

  master
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
PostgreSQL Telnet Interface

database name: postgres
username: kuntal
password: changeme
> select 1;
?column?
----
1

SELECT 1
> select 1/0;
Message: ERROR - division by zero

Few comments in the extension code (although experimental):

1. In telnet_srv.c,
+ static int pe_port;
..
+ DefineCustomIntVariable("telnet_srv.port",
+ "Telnet server port.",
+ NULL,
+ &pe_port,
+ pe_port,
+ 1024,
+ 65536,
+ PGC_POSTMASTER,
+ 0,
+ NULL,
+ NULL,
+ NULL);

The variable pe_port should be initialized to a value which is > 1024
and < 65536. Otherwise, the following assert will fail,
TRAP: FailedAssertion("newval >= conf->min", File: "guc.c", Line:
5541, PID: 12100)

2. The function pq_putbytes shouldn't be used by anyone other than
old-style COPY out.
+ pq_putbytes(msg, strlen(msg));
Otherwise, the following assert will fail in the same function:
/* Should only be called by old-style COPY OUT */
Assert(DoingCopyOut);

--
Thanks & Regards,
Kuntal Ghosh
Amazon Web Services