Re: Extensibility of the PostgreSQL wire protocol

On Thu, Feb 18, 2021 at 9:32 PM Jan Wieck <jan@wi3ck.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