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| author | David Rowley | 2021-08-22 11:31:16 +0000 |
|---|---|---|
| committer | David Rowley | 2021-08-22 11:31:16 +0000 |
| commit | 22c4e88ebff408acd52e212543a77158bde59e69 (patch) | |
| tree | 41b320c366b66ca4fa724259e79b4ceb2a696d2d /src/include | |
| parent | 26ae66090398082c54ce046936fc41633dbfc41e (diff) | |
Allow parallel DISTINCT
We've supported parallel aggregation since e06a38965. At the time, we
didn't quite get around to also adding parallel DISTINCT. So, let's do
that now.
This is implemented by introducing a two-phase DISTINCT. Phase 1 is
performed on parallel workers, rows are made distinct there either by
hashing or by sort/unique. The results from the parallel workers are
combined and the final distinct phase is performed serially to get rid of
any duplicate rows that appear due to combining rows for each of the
parallel workers.
Author: David Rowley
Reviewed-by: Zhihong Yu
Discussion: https://postgr.es/m/CAApHDvrjRxVKwQN0he79xS+9wyotFXL=RmoWqGGO2N45Farpgw@mail.gmail.com
Diffstat (limited to 'src/include')
| -rw-r--r-- | src/include/nodes/pathnodes.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h index 6e068f2c8b3..1abe233db2b 100644 --- a/src/include/nodes/pathnodes.h +++ b/src/include/nodes/pathnodes.h @@ -71,6 +71,7 @@ typedef enum UpperRelationKind * any */ UPPERREL_GROUP_AGG, /* result of grouping/aggregation, if any */ UPPERREL_WINDOW, /* result of window functions, if any */ + UPPERREL_PARTIAL_DISTINCT, /* result of partial "SELECT DISTINCT", if any */ UPPERREL_DISTINCT, /* result of "SELECT DISTINCT", if any */ UPPERREL_ORDERED, /* result of ORDER BY, if any */ UPPERREL_FINAL /* result of any remaining top-level actions */ |