Bug in pgbench prepared statements

Hi,

I noticed something that looks like a bug in pgbench when using the
prepared protocol. pgbench assumes that all prepared statements are
prepared correctly, even if they contain errors (e.g. syntax, column/table
doesn't exist, etc.).

My test script is just:

SELECT one;

The output looks something like this:

$ pgbench -f test.sql --protocol prepared -d postgres

[...]
pgbench: client 0 executing script "test.sql"
pgbench: client 0 preparing P_0
pgbench: error: ERROR: column "one" does not exist
LINE 1: SELECT one;
^
pgbench: client 0 sending P_0
pgbench: client 0 receiving
pgbench: client 0 receiving
pgbench: error: client 0 script 0 aborted in command 0 query 0: ERROR:
prepared statement "P_0" does not exist
transaction type: test.sql
[...]

Normally this wouldn't be a big deal, although by itself the output is
confusing, since the second error, while technically true, is not what
caused the test run to fail. In my case, I was using pgbench to validate
the correctness of prepared statements implementation in our pooler. Having
the second error sent me on quite a debugging session until I realized that
my fix was actually working.

Patch attached, if there is any interest in fixing this small bug.

Cheers!

Lev
postgresml.org