Re: [hibernate-dev] [OGM] Id generation strategies

On 19 Jun 2014, at 14:54, Gunnar Morling <gunnar(a)hibernate.org&gt; wrote: 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? > It would look like this: { "_id" : 1, "value1" : 10, "value2" : 24 } So you would get the different sequence values from different fields of that same document. But I wouldn't recommend to do so due to the potential contention on that single record. Thus I'd raise at least a warning during bootstrap. As it's not portable to stores with a fixed schema, I'd rather not support it at all, though, and raise an error. Exactly. But that’s the thing, AFAIK we do *not* store it that way today as we don’t use valueColumnName. So today we store it like this { “_id”: 1, “sequence_value”: 10 } so 10 and 24 has to both live at the same time in sequence _value.