Re: [Hibernate-devel] The beauty of multiple tables in polymorphic persistency?

[Viktor S. <phr...@im...>]

hi,

Roman Seidl wrote:

>
> Is it a performance benefit to map to multiple tables? If not it might 
> be useless anyway - might depend on the database...
>
usually you don't do it for the  perf. benefit, but for other useful 
aspects. imho it makes data maintenance easier in the long run (eg. 
schema chgs, or adding db constraints), not to mention easthetic 
pleasure (or just ease-of-use w/ reporting tools) or db limitiations 
(nobody likes too many columns)...

on the performance side:
 - writing definitely becomes worse
 - reading might become worse (depending on db and your queries)
 - space consumption is better

>
>Usually it would be a performance *loss*, except for very deep class
>heirarchies. However, for people mapping legacy data or for people
>
umm.. i think it would become worse as the hierarchy gets deeper...

    viktor