Re: pg_migrator issues - Mailing list pgsql-hackers

Bruce Momjian wrote:
> pg_migrator has become more popular recently, so it seems time to look
> at some enhancements that would improve pg_migrator.  None of these are
> required, but rather changes that would be nice to have:
> 
> 1)  Right now pg_migrator preserves relfilenodes for TOAST files because
> this is required for proper migration.  Now that we have shown that
> strategically-placed global variables with a server-side function to set
> them is a viable solution, it would be nice to preserve all relfilenodes
> from the old server.  This would simplify pg_migrator by no long
> requiring place-holder relfilenodes or the renaming of TOAST files.  A
> simpler solution would just be to allow TOAST table creation to
> automatically remove placeholder files and create specified relfilenodes
> via global variables.
> 
> 2)  Right now pg_migrator renames old tablespaces to .old, which fails
> if the tablespaces are on mount points.  I have already received a
> report of such a failure.  $PGDATA also has that issue, but that
> renaming has to be done by the user before pg_migrator is run, and only
> if they want to keep the same $PGDATA value after migration, i.e. no
> version-specific directory path.  One idea we floated around was to have
> tablespaces use major version directory names under the tablespace
> directory so renaming would not be necessary.  I could implement a
> pg_migrator --delete-old flag to cleanly delete the old 8.4 server files
> which are not in a version-specific subdirectory.
> 
> 3)  There is no easy way to analyze all databases.  vacuumdb --analyze
> does analyze _and_ vacuum, which for an 8.4 to 8.5 migration does an
> unnecessary vacuum.  Right now I recommend ANALYZE in every database,
> but it would be nice if there were a single command which did this.
> 
> 4)  I have implemented the ability to run pg_migrator --check on a live
> old server.  However, pg_migrator uses information from controldata to
> check things, and it also needs xid information that is only available
> via pg_resetxlog -n(no update) to perform the migration.  Unfortunately,
> pg_resetxlog -n cannot be run on a live server, so pg_migrator runs
> pg_controldata for --check and pg_resetxlog -n for real upgrades.  It
> would simplify pg_migrator if I would run pg_resetxlog -n on a live
> server, but I can understand if people don't want to do that because the
> xid information reported on a live server is inaccurate.

FYI, for those keeping score, I have posted patches for #1 and #3, and
we have decided not to implement #2 and #4.

--  Bruce Momjian  <bruce@momjian.us>        http://momjian.us EnterpriseDB
http://enterprisedb.com
 + If your life is a hard drive, Christ can be your backup. +