A single-statement SQL PageRank implementation sounds feasible to me. Most commercial SQL implementations have had hierarchal, ranking, and windowing functions for a while now. They all have XML (maybe HTML?) document parsers in them as well. I think moderately complex hierarchical rankings can be built from those primitives, even as a single SQL statement.
The performance of that code and if/how they are parallelized by the system is really a quality-of-implementation issue. If Oracle, Microsoft, or IBM thinks they can make money by implementing automatically parallelized hierarchical ranking and windowing functions, they will do so; maybe some of them have already done so.
I share Oracle's philosophy about how abstract SQL should be. Oracle says you should be able to write the same SQL against a small single-instance database that you would write against a giant multi-instance database; the database is responsible for optimizing the performance, not the developer. There are a lot of cases where the theory doesn't match practice with Oracle, but every new release gets the two closer. I wouldn't be surprised to see Oracle surpass general-purpose MapReduce-based approaches in terms of performance soon. And, I am expecting Oracle to release a tool to efficiently run MapReduce-style programs against Oracle (converting them to SQL) any time now.
The performance of that code and if/how they are parallelized by the system is really a quality-of-implementation issue. If Oracle, Microsoft, or IBM thinks they can make money by implementing automatically parallelized hierarchical ranking and windowing functions, they will do so; maybe some of them have already done so.
I share Oracle's philosophy about how abstract SQL should be. Oracle says you should be able to write the same SQL against a small single-instance database that you would write against a giant multi-instance database; the database is responsible for optimizing the performance, not the developer. There are a lot of cases where the theory doesn't match practice with Oracle, but every new release gets the two closer. I wouldn't be surprised to see Oracle surpass general-purpose MapReduce-based approaches in terms of performance soon. And, I am expecting Oracle to release a tool to efficiently run MapReduce-style programs against Oracle (converting them to SQL) any time now.