3 ms·

They mention that it's super fast without index. Is there a win with index ?

• tmostak 10y ago
  The main focus of MapD is scan queries where you might need to look at billions of rows to do the group bys, joins and aggregates to answer a query. Indexes don't tend to do well for such use cases. In the future we may add indexes such that looking up a single or small number of rows is as fast as possible (such operations fast now since the GPU scans are so fast, but not as fast as they would be if we had indexes)
  • joe_the_user 10y ago
    So does the database essentially feed the tables referenced in the query through the gpu? Does it accumulate values as it goes? Work on all the values together in memory? Anyway, it seems like this sort of speed should also allow one to work with larger indices and do the sort of queries that allows.
    • tmostak 10y ago
      MapD tries to cache compressed versions of the "hot" columns of a table in GPU RAM, which could be up to 256GB per node across 8 GPUs. If necessary though it can stream the data from CPU RAM - of course such queries won't be as fast. Yes you could imagine accelerating index lookups with GPUs (I think there's some research papers on this subject already) - maybe a future project for us.