[PATCH] pgbench: new feature allowing to launch shell commands

Hi all,

Here is a short patch implementing a new feature in pgbench so as to allow
shell commands to be launched in a transaction file of pgbench.
the user has just to add at the beginning of the command line in his
transaction file \shell + the command wanted.

As an example of transaction:
Begin;
[Transaction instructions]
Prepare transaction ‘TXID’;
\shell ls ~/pg_twophase;
Commit prepared ‘TXID’;

This patch was particularly useful in order to determine the size of state
files flushed to disk for prepared but not committed transactions.
As an addition, I added a new default transaction in the code that permits
to launch a 2PC transaction with a random prepare identifier of the format
Txxx.

I also created a page in postgresql's wiki about this feature.
Please refer to this link:
http://wiki.postgresql.org/wiki/Pgbench:_shell_command

Regards,

--
Michael Paquier

NTT OSSC