[hibernate-dev] [OGM] Id generation strategies

[Emmanuel Bernard]

On 19 Jun 2014, at 11:12, Gunnar Morling <gunnar at hibernate.org> wrote:

> I'm looking into this atm.
> 
> My thinking is to pass a new dedicated Type IdGeneratorKey instead of RowKey to GridDialect#nextVal() which can carry all the information we need. The dual use of RowKey for association rows and sequences has been confusing anyways.

Yes that’s a good idea.

> 
> 2014-06-06 10:44 GMT+02:00 Emmanuel Bernard <emmanuel at hibernate.org>:
> I guess it is particularly questionable to have an identity generator be mapped to an ad-hoc table based generator. Remember the angle we came from: make a JPA application work when storing data in Infinispan. Unlike other datastores, Infinispan has not notion of id generation whatsoever.
> 
> sequenceName should map to on of the OgmTableGenetator settings somehow.
> 
> +1
>  
> valueColumnName is something that I elected no to use because NoSQL we bind to so far do not have a strong schema. And at at given segmentColumnValue only correspond a single value. It would come and bite me if someone for the same segment value had two different value column names to differentiate two different sequence.
> 
> Would it really bite you? I think e.g. MongoDB could perfectly handle this case via two different fields for the two sequences in the same document/segment.

@TableGenerator(
	name=“1”,
	table=“Seq_table”,
	pkColumnName=“key”,
	pkColumnValue=“1”,
	valueColumnName=“value1”
)
@TableGenerator(
	name=“2”,
	table=“Seq_table”,
	pkColumnName=“key”,
	pkColumnValue=“1”,
	valueColumnName=“value2”
)

The two definitions share the same options except for valueColumnName.
The table is roughly as followed

TABLE(Seq_table)
key    |    value1   |   value2
1        |   10           |  24

What would be the MongoDB representation in your approach?

> 
> But as this does not really seem like a best practice, we could also handle it as a definition error if the same table is used with different value column names in different generators. We could raise an error during bootstrap.

I am not a huge fan but I could live with that as long as it is detectable.