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

On 24 Jun 2014, at 11:50, Gunnar Morling <gunnar(a)hibernate.org&gt; wrote: Yes, today we don't. But is there any reason for not using the value column name? Not more that the ones I outlined in this thread. In fact that's what my pending PR https://github.com/hibernate/hibernate-ogm/pull/337 does for MongoDB. Right now it even allows to work with different value column names for the same table (either in the same or in different documents/records) but I plan to add a check disallowing this for the sake of portability to stores with a fixed schema. I don’t follow that one. A fixed schema would be fine here, just with two columns instead of one, no?

2014-06-20 13:00 GMT+02:00 Emmanuel Bernard <emmanuel(a)hibernate.org&gt;: > > 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. > >