Re: Recursive queries in slow database

David BL wrote:

>> Google for, and read about the Entity-Attribute-Value (EAV) Model, which
>> is what your description of their approach sounds like. You will find
>> ample discussion of why it is bad--not the least reason being that its
>> practitioners are reimplementing the very thing an SQL DBMS is designed
>> to do. It is invariably done only partially too, leaving out almost
>> all of the important stuff a DBMS does, like providing data integrity
>> checks, transaction isolation, etc.
>
> How does using EAV on top of an SQL DBMS leave out transaction
> isolation? I would have thought you could use an arbitrarily bad
> schema and still have serialisability of transactions assuming the
> underlying DBMS uses SS2PL.

Sorry, I conflated two problems. EAV per se need not have an adverse impact on transaction isolation. It's the implementations of EAV I have seen, in which it is very difficult to know in advance (i.e. when coding) which pseudo-table you are working with. If you don't know the conceptual model that is in effect you can't know when you've put the database into a new consistent state and hence you can't know that it's wrong to COMMIT or not.

-- 
Roy