Re: pg_migrator issues

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.
>
> Comments?

Having received no replies to my email above, I assume the community
would like to review and perhaps approve patches to implement all of
these items. I will start working on the patches.

--
Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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