Monday, May 12, 2008
Getting more violent all the timeThe distinguished Mr. Cameron has restated what he thinks is our major disagreement over synchronization and replication of identity data on the so-called "identity bus." He says:
"Sometimes an application needs to do complex searches involving information 'mastered' in multiple locations. I’ll make up a very simple 'two location' example to demonstrate the issue:
What Kim fails to note, however, is that a well designed virtual directory (see Radiant Logic's offering, for example) will allow you to do a SQL query to the virtual tables! You get the best of both: up to date data (today's new hires and purchases included) with the speed of an SQL join. And all without having to replicate or synchronize the data. I'm happy, the application is happy - and Kim should be happy too. We are in violent agreement about what the process should look like at the 40,000 foot level and only disagree about the size and shape of the paths - or, more likely, whether they should be concrete or asphalt.
But the issue is not with the language you use to perform the query: it's where the data is located. If you have data in separate physical databases then it's necessary to pull the data from the separate sources and join them locally. So, in Kim's example, if you have 5000 employees and have sold 10000 computers then you need to pull down the 15000 records over the network and perform the join locally (unless you have an incredibly smart distributed query optimiser which works across heterogeneous data stores). This is going to be more expensive than if the computer order and employee data are colocated.Post a Comment
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