I think that might be a good idea --- it'd reduce the cross-platform variability of the results quite a bit, I suspect. random() is not to be trusted everywhere, but I think erand48 is pretty much the same wherever it exists at all (and src/port/ provides it elsewhere).
Given that pgbench will run with threads in some multi-worker configurations, after some more portability research I think odds are good we'd get nailed by http://sourceware.org/bugzilla/show_bug.cgi?id=10320 : "erand48 implementation not thread safe but POSIX says it should be". The AIX docs have a similar warning on them, so who knows how many versions of that library have the same issue.
Maybe we could make sure the one in src/port/ is thread safe and make sure pgbench only uses it. This whole area continues to be messy enough that I think the patch needs to brew for another CF before it will all be sorted out properly. I'll mark it accordingly and can pick this back up later.
Hi Greg,
I spent some time rebasing this patch to current master. Attached is the patch, based on master couple of commits old.
Your concern of using erand48() has been resolved since pgbench now uses thread-safe and concurrent pg_erand48() from src/port/.
The patch is very much what you had posted, except for a couple of differences due to bit-rot. (i) I didn't have to #define MAX_RANDOM_VALUE64 since its cousin MAX_RANDOM_VALUE is not used by code anymore, and (ii) I used ternary operator in DDLs[] array to decide when to use bigint vs int columns.
Please review.
As for tests, I am currently running 'pgbench -i -s 21474' using unpatched pgbench, and am recording the time taken;Scale factor 21475 had actually failed to do anything meaningful using unpatched pgbench. Next I'll run with '-s 21475' on patched version to see if it does the right thing, and in acceptable time compared to '-s 21474'.
What tests would you and others like to see, to get some confidence in the patch? The machine that I have access to has 62 GB RAM, 16-core 64-hw-threads, and about 900 GB of disk space.
Linux <host> 3.2.6-3.fc16.ppc64 #1 SMP Fri Feb 17 21:41:20 UTC 2012 ppc64 ppc64 ppc64 GNU/Linux