Am 07.02.2013 21:18, schrieb Jürgen Herrmann:
Am 07.02.2013 20:22, schrieb Shane Hathaway:
On 02/06/2013 04:23 AM, Jürgen Herrmann wrote:
I think this is not entirely correct. I ran in to problems serveral
times when new_oid was emptied! Maybe Shane can confirm this?
(results in read conlfict errors)


Ah, that's true. You do need to replicate new_oid.

Then I'd like to talk a little about my current relstorage setup here:
It's backed by mysql, history-preserving setup. Recently one of our
DBs started to grow very quickly and it's object_state.ibd (InnoDB)
file is just over 86GB as of today. Packing now fails due to mysql
not being able to complete sorts in the object_ref table. object_ref is also very big (36GB MYD file, 25GB MYI file). I took a backup of the DB and let zodbconvert convert it back to a FileStorage, the resulting
file is 6GB (!). I will pack it and see how big it is then. I will
also investigate how big on disk this DB would be when stored in
postgresql. This situation poses another problem for us: using
zodbconvert to convert this mess to a Filestorage tages just over an
hour when writing to a ramdisk. I suspect converting to postgres
will take more than 10 hours, which is unacceptable for us as this
is a live database an cannot be offline for more than 2-3 hours in
the nicht. So we will have to investigate into a special zodbconvert
that uses a two step process:
1. import transactions to new storage from a mysql db backup
2. import "rest" of transactions that occurred after the backup was
    made from the "live" database (which is offline for that time
    of course)

looking at zodbconvert using copyTransactionsFrom() i thnik this
should be possible but up to now i did non investigate furhter.
maybe shane could confirm this? maybe this could also be transformed
into a neat way of getting incremental backups out of zodbs in
general?

Yes, that could work.

As for MySQL growing tables without bounds... well, that wouldn't
surprise me very much.

I know that's entirely not your fault but may be worth mentioning
in the docs. Relstorage with MySQL works *very* well for DB sizes
<5GB or so, above that - not so much :/

Also for the docs: on disk Restorage/MySQL uses 4x the size of a
FileStorage with same contents. As packing tables are filled this
grows by another factor of ~2. If you don't pack very regularly
you might up ending in DBs that donb't permit packing anymore
because of the big size very quickly.

best regards,
Jürgen


That issue has given me some sleepless nights, especially because
the conversion step to another storage type takes quite a long
time. But in less than two hours i came up with a workable
solution today, maybe see the other messages on the list regarding
that issue. I LOVE OPEN SOURCE. I LOVE PYTHON. :)

best regards,
Jürgen
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Boelckestrasse 21, 93051 Regensburg, Germany

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