Well, one of the things is that OJB uses a common schema for all databases. Some of the currrent RDBMS stores use integer while others use long for the id fields. I chose long, but that shouldn't be much of a problem. I also changed the date fields to map to SQL TIMESTAMP type instead of long. However, the type mappings can be easily changed in OJB without changing the code. But the biggest difference is the handling of the multivalue properties. For multivalue properties the values are stored in a separate table. I think I can implement some way to detect if the multivalue properties are stored in the new format or the old one and do the appropiate thing. Maybe add an auto-migrate option to convert from the old format to the new one on saving.

Once I finish the content store bit and I have the full store working I'll revisit these issues. Schema compatibility wasn't my priority as long as I provided some migration tool, I thought. But I'll see if I can simplify the migration path by trying to eliminate the dump/restore requirenment.


Carlos


Warwick Burrows wrote:
Oops. I should have finished reading your email. The OJB changes will
definitely require data migration then...  What kind of changes are we
talking about?

Thanks.



-----Original Message-----
From: Warwick Burrows Sent: Thursday, February 10, 2005 8:03 PM
To: Slide Users Mailing List
Subject: Will OJB require db migration?




Carlos, will the new OBJ store implementation require that we migrate our Slide 2.1 databases (ouch!) or will the schema generated by OJB match the existing schema for our DBs? We will shortly release our current product on Slide 2.1 with many, many thousands of files. We plan to release our next product on Slide 2.2.

Thanks,
Warwick



-----Original Message-----
From: Carlos Villegas [mailto:[EMAIL PROTECTED]
Sent: Thursday, February 10, 2005 7:59 PM
To: Slide Users Mailing List
Subject: Re: max revision limit?


Yes, I implemented the proposed solution in the new OJB store
available from CVS head. The OJB store is meant to replace the RDBMS

stores but


it's not finished yet, the content store bit is not done. If you want to test it and verify that solves the problem, you can combine it with the txfile store, for instance: use txfile for content and OJB for the rest, a sample Domain.xml file is available in src/conf/ojb. The database schema of the OJB store is not exactly the same as the

current RDBMS


stores so part of the work is to write some migration tool as well. That needs to be done also.

I'll be working on finishing the OJB content store

implementation but

progress is slow since I have a very busy schedule at work

right now.

Carlos

Luke Noel-Storr wrote:

Hi,

I was just wondering if you'd made any progress with this?

I've come up against this problem again now we are using

a database


backed version of Slide again, and it would be great if a

solution was

in the pipeline.

It's certainly a design flaw as it is, and I can no

longer make the


fields in my database bigger (which just puts off the

problem anyway)

without changing them to blobs (which will also require a

code change).


Cheers

Luke.
-----



Carlos Villegas wrote:


Ok. I'll work on it. I'm quite busy at work but I'll

make some time


for this.

Carlos

James Mason wrote:


Carlos,

This seems valuable to me as well. Multivalue properties

are a bit

of
a pain to work with right now.

-James

Warwick Burrows wrote:


Hi Carlos,

I definitely think its worth it. How were you thinking

of indexing

this second table? The way to uniquely identify any individual
property in the property table seems to require 3 fields -- property namespace, property
name and version id? That would indicate that any table

you create

would
need all three of these as the primary key?

Warwick


-----Original Message-----
From: Carlos Villegas [mailto:[EMAIL PROTECTED] Sent: Tuesday, September 07, 2004 8:40 PM
To: Slide Users Mailing List
Subject: Re: max revision limit?





Warwick Burrows wrote:


Yes, but how much bigger? :-) It seems to be a flaw in

the design

that there is a version property that constantly grows

in length

with each new version added. Is this the way the spec

defined the

value of this property, or is this just Slide's

implementation?





It seems to me it's a design flaw.

There are several properties that are a list of values

like history

and group-member-set. I was thinking of adding a type

identifier

field to the properties table and storing the individual

values in

a different table, one
per row. That's the usual relational db solution to

this problem.

BTW, there's a property_type field in the properties

table and the

Java object also has this field, but it doesn't seem to

be used. Is

it used at all? If is not can we use it for this purpose?

I volunteer to try to fix at least one of the database

stores using

this
technique if anybody thinks it's worth it.

Carlos



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