Allow UPDATE to move rows between partitions.

When an UPDATE causes a row to no longer match the partition
constraint, try to move it to a different partition where it does
match the partition constraint.  In essence, the UPDATE is split into
a DELETE from the old partition and an INSERT into the new one.  This
can lead to surprising behavior in concurrency scenarios because
EvalPlanQual rechecks won't work as they normally did; the known
problems are documented.  (There is a pending patch to improve the
situation further, but it needs more review.)

Amit Khandekar, reviewed and tested by Amit Langote, David Rowley,
Rajkumar Raghuwanshi, Dilip Kumar, Amul Sul, Thomas Munro, Álvaro
Herrera, Amit Kapila, and me.  A few final revisions by me.

Discussion: http://postgr.es/m/CAJ3gD9do9o2ccQ7j7+tSgiE1REY65XRiMb=yJO3u3QhyP8EEPQ@mail.gmail.com

1 files changed, 4 insertions, 0 deletions

diff --git a/src/backend/optimizer/util/pathnode.c b/src/backend/optimizer/util/pathnode.c
index fa4b4683e5c..91295ebca49 100644
--- a/src/backend/optimizer/util/pathnode.c
+++ b/src/backend/optimizer/util/pathnode.c
@@ -3274,6 +3274,8 @@ create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
  * 'partitioned_rels' is an integer list of RT indexes of non-leaf tables in
  *		the partition tree, if this is an UPDATE/DELETE to a partitioned table.
  *		Otherwise NIL.
+ * 'partColsUpdated' is true if any partitioning columns are being updated,
+ *		either from the target relation or a descendent partitioned table.
  * 'resultRelations' is an integer list of actual RT indexes of target rel(s)
  * 'subpaths' is a list of Path(s) producing source data (one per rel)
  * 'subroots' is a list of PlannerInfo structs (one per rel)
@@ -3287,6 +3289,7 @@ ModifyTablePath *
 create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 						CmdType operation, bool canSetTag,
 						Index nominalRelation, List *partitioned_rels,
+						bool partColsUpdated,
 						List *resultRelations, List *subpaths,
 						List *subroots,
 						List *withCheckOptionLists, List *returningLists,
@@ -3354,6 +3357,7 @@ create_modifytable_path(PlannerInfo *root, RelOptInfo *rel,
 	pathnode->canSetTag = canSetTag;
 	pathnode->nominalRelation = nominalRelation;
 	pathnode->partitioned_rels = list_copy(partitioned_rels);
+	pathnode->partColsUpdated = partColsUpdated;
 	pathnode->resultRelations = resultRelations;
 	pathnode->subpaths = subpaths;
 	pathnode->subroots = subroots;