Re: [HACKERS] Partition-wise aggregation/grouping

Hi,

In this attached version, I have rebased my changes over new design of partially_grouped_rel. The preparatory changes of adding partially_grouped_rel are in 0001.

Also to minimize finalization code duplication, I have refactored them into two separate functions, finalize_sorted_partial_agg_path() and finalize_hashed_partial_agg_path(). I need to create these two functions as current path creation order in like,
    Sort Agg Path
    Sort Agg Path - Parallel Aware (Finalization needed here)
    Hash Agg Path
    Hash Agg Path - Parallel Aware (Finalization needed here)
And if we club those finalizations together, then path creation order will be changed and it may result in the existing plan changes.
Let me know if that's OK, I will merge them together as they are distinct anyways. These changes are part of 0002.

0003 - 0006 are refactoring patches as before.

0007 is the main patch per new design. I have removed create_partition_agg_paths() altogether as finalization code is reused. Also, renamed preferFullAgg with forcePartialAgg as we forcefully needed a partial path from nested level if the parent is doing a partial aggregation. add_single_path_to_append_rel() is no more exists and also there is no need to pass OtherUpperPathExtraData to add_paths_to_append_rel().

0008 - 0009, testcase and postgres_fdw changes.

Please have a look at new changes and let me know if I missed any.

Thanks