Re: Updated version of pg_receivexlog

> + 		/*
> + 		 * Looks like an xlog file. Parse it's position.

s/it's/its/

> + 		 */
> + 		if (sscanf(dirent->d_name, "%08X%08X%08X", &tli, &log, &seg) != 3)
> + 		{
> + 			fprintf(stderr, _("%s: could not parse xlog filename \"%s\"\n"),
> + 					progname, dirent->d_name);
> + 			disconnect_and_exit(1);
> + 		}
> + 		log *= XLOG_SEG_SIZE;

That multiplication by XLOG_SEG_SIZE could overflow, if logid is very 
high. It seems completely unnecessary, anyway,

s/IDENFITY_SYSTEM/IDENTIFY_SYSTEM/ (two occurrences)

In pg_basebackup, it would be a good sanity check to check that the 
systemid returned by IDENTIFY_SYSTEM in the main connection and the 
WAL-streaming connection match. Just to be sure that some connection 
pooler didn't hijack one of the connections and point to a different 
server. And better check timelineid too while you're at it.

How does this interact with synchronous replication? If a base backup 
that streams WAL is in progress, and you have synchronous_standby_names 
set to '*', I believe the in-progress backup will count as a standby for 
that purpose. That might give a false sense of security. 
synchronous_standby_names='*' is prone to such confusion in general, but 
it seems that it's particularly surprising if a running pg_basebackup 
lets a commit in synchronous replication to proceed. Maybe we just need 
a warning in the docs. I think we should advise that 
synchronous_standby_names='*' is dangerous in general, and cite this as 
one reason for that.

-- 
   Heikki Linnakangas
   EnterpriseDB   http://www.enterprisedb.com