On Fri, May 8, 2015 at 9:34 PM, Heikki Linnakangas <hlinnaka@iki.fi> wrote:
On 05/08/2015 03:25 PM, Vladimir Borodin wrote:
Seems, that pg_rewind does not account --dry-run option properly. A simple fix for that is attached.
No, the --dry-run takes effect later. It performs all the actions it normally would, including reading files from the source, except for actually writing anything in the target. See the dry-run checks in file_ops.c
Urgh, my test script had an error and I made grep only in pg_rewind.c. Sorry for noise.
Even if the patch sent is incorrect, shouldn't there be some process bypass in updateControlFile() and createBackupLabel() in case of a --dry-run?
They both use open_target_file() and write_target_file(), which check for --dry-run and do nothing if it's set.
Hmm, I wonder it we should print something else than "Done!" at the end, if run in --dry-run mode. Or give some indication around the time it says "Rewinding from last common checkpoint at ...", that it's running in dry-run mode and won't actually modify anything. The progress messages are a bit alarming if you don't realize that it's skipping all the writes.
That would be really nice.
Wouldn't hurt to also augment that rather doom-looking "point of no return" comment with a note that says writes won't happen if in dry-run. :)
