pg_resetsysid

Hi,

This is an attempt to revive the resetsysid tool submission that didn't
go anywhere last year [1].

In that thread there were mainly two complains, one that pg_resetxlog
would preferably be tool for more advanced stuff and similar utilities
that are not as dangerous should have separate binaries using some of
the functionality of pg_resetxlog as library and the other was with the
string to uint64 parsing which is apparently not so easy to do portably.
About the second one there was also separate discussion between Andres
and Tom [2].

Here is series of patches that implements both the original feature and
solves the issues mentioned above.

0001 - This patch splits the code of pg_resetxlog to common.c/h api and
pg_resetxlog.c itself which does the program logic using the api. The
only logical change in the XLogSegNoOffsetToRecPtr call is moved into
main() function, which I think is ok as the main() does all the other
ControlFile changes. All other changes should be just cosmetic in order
to not rely on global static variables.

0002 - Adds pg_resetsysid utility which changes the system id to newly
generated one.

0003 - Adds -s option to pg_resetxlog to change the system id to the one
specified - this is separate from the other one as it can be potentially
more dangerous. It also adds some defines that try to portably map
pg_strtoint64 and pg_strtouint64 to the underlying implementations
(strtol/strtoll/_strtoi64 and unsigned variants of those). It will leave
the pg_strtoint64/pg_strtouint64 undefined if the platform does not
support the functionality. Tom was unsure if there are such platforms on
our supported list anymore.

Which is why I also added 0004, that adds fall-back implementation of
the two functions based on very slightly modified code from OpenBSD.
This is here mostly in case buildfarm gets red after applying 0003 or we
have reports from users that things got broken.

[1] http://www.postgresql.org/message-id/539B97FC.8040806@2ndquadrant.com
[2]
http://www.postgresql.org/message-id/20140603144654.GM24145@awork2.anarazel.de

--
  Petr Jelinek                  http://www.2ndQuadrant.com/
  PostgreSQL Development, 24x7 Support, Training & Services