Why isn't the GROUP BY operator evaluated remotely?

There are several areas that you can check to determine why a GROUP BY operator is not evaluated remotely.

The areas that you can check include:
  • Is the input to the GROUP BY operator evaluated remotely? If the answer is no, examine the input.
  • Does the data source have any restrictions on this operator? Examples include:
    • Limited number of GROUP BY items
    • Limited byte counts of combined GROUP BY items
    • Column specification only on the GROUP BY list
  • Does the data source support this SQL operator?
  • Global optimization. The optimizer decided that local processing is more cost-effective.