[hibernate-dev] Data encoding change for Hibernate OGM / Infinispan Embedded

[Sanne Grinovero]

To fix the sequence generation consistency issue on Infinispan
Embedded [OGM-1212] I will need to change how sequences
are encoded within the datagrid.

This means OGM 5.2 will be able to read data as encoded by previous
versions, but it will write data using a new format.

This has some implications, such as people upgrading temporarily to
OGM 5.2 can't go back to previous versions (without restoring a backup
of the data).
I will document this limitation.

There's a second aspect:

OGM will now include some code to be able to read pre-5.1 data, but
eventually we'll want to remote this. How should we handle that?

I'm thinking that people hitting this problem (in some future) will
simply need to fetch OGM 5.2 and use that as an intermediate step;
however OGM will only upgrade the data encoding "lazily" as it goes
along: when something happens to be read, and happens to be
re-written, it will re-encode it.
But some data might never be rolled over to the new format.

So I think we'll eventually need a data migration tool which performs
all data-encoding aspects eagerly, so that it can report a point in
time for which it's done and safe to move on to a future version.
I don't wish to create such a tool now for OGM version 5.2 but I
we should agree on a plan already.

I also wonder if this should mark the following issue "out of date":
 - https://hibernate.atlassian.net/browse/OGM-1148

Thanks,
Sanne