http://ayende.comAyende @ RahienCopyright (C) Ayende Rahien 2004 - 2021 (c) 202660__In particular, making schema changes or adding indexes to a database with more than 10 - 20 million rows completely locks the database for hours at a time. In MySql -- yes. It is the single worst performing DB I have ever worked with, especially considering index changes. Finding the workarounds for this can not be considered a breakthrough -- it would be much better if they just fixed it. However, I do not yet see a value in having a schema-less DB2 or Sql Server (but it might be I just had no real use case). http://ayende.com/3896/schema-less-databases#comment4http://ayende.com/3896/schema-less-databases#comment4Tue, 10 Mar 2009 10:54:35 GMTGreat read. RDBMS are meant to be performant and scalable, and maybe they are. But their manageability ends quickly when amount of data grows. I have very similar experience with a system built on top of SQL Server and an OR mapper. The system was meant for high availability, but upgrades are now very time consuming and dangerous because it takes hours to update database structure. You have only one chance to update database, because if something goes wrong you dont have time to retry in service time. What's worse, rollback takes the same time as completing the operation. If I were designing the software again, I'd consider a more unstructured approach with custom indexing instead of rigid relational structure. http://ayende.com/3896/schema-less-databases#comment3http://ayende.com/3896/schema-less-databases#comment3Mon, 09 Mar 2009 18:33:08 GMTAnd now that I read the second link, I see that it does in fact speak of GData's approach. Huh. http://ayende.com/3896/schema-less-databases#comment2http://ayende.com/3896/schema-less-databases#comment2Mon, 09 Mar 2009 00:15:04 GMTThis is a very interesting subject. The trick is to know when to use it - on large, scalable systems, which seems counter-intuitive since normal RDBMS usage is intended for large, scalable systems. When do you use RDBMS, then, and when do you use this approach? (Which is quite simple to google's approach with GData, I might add). http://ayende.com/3896/schema-less-databases#comment1http://ayende.com/3896/schema-less-databases#comment1Mon, 09 Mar 2009 00:05:34 GMT