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, 16 insertions, 3 deletions

diff --git a/src/backend/optimizer/plan/planner.c b/src/backend/optimizer/plan/planner.c
index 7b52dadd817..53870432ea7 100644
--- a/src/backend/optimizer/plan/planner.c
+++ b/src/backend/optimizer/plan/planner.c
@@ -1101,6 +1101,7 @@ inheritance_planner(PlannerInfo *root)
 	Query	   *parent_parse;
 	Bitmapset  *parent_relids = bms_make_singleton(top_parentRTindex);
 	PlannerInfo **parent_roots = NULL;
+	bool		partColsUpdated = false;
 
 	Assert(parse->commandType != CMD_INSERT);
 
@@ -1172,7 +1173,8 @@ inheritance_planner(PlannerInfo *root)
 	if (parent_rte->relkind == RELKIND_PARTITIONED_TABLE)
 	{
 		nominalRelation = top_parentRTindex;
-		partitioned_rels = get_partitioned_child_rels(root, top_parentRTindex);
+		partitioned_rels = get_partitioned_child_rels(root, top_parentRTindex,
+													  &partColsUpdated);
 		/* The root partitioned table is included as a child rel */
 		Assert(list_length(partitioned_rels) >= 1);
 	}
@@ -1512,6 +1514,7 @@ inheritance_planner(PlannerInfo *root)
 									 parse->canSetTag,
 									 nominalRelation,
 									 partitioned_rels,
+									 partColsUpdated,
 									 resultRelations,
 									 subpaths,
 									 subroots,
@@ -2123,6 +2126,7 @@ grouping_planner(PlannerInfo *root, bool inheritance_update,
 										parse->canSetTag,
 										parse->resultRelation,
 										NIL,
+										false,
 										list_make1_int(parse->resultRelation),
 										list_make1(path),
 										list_make1(root),
@@ -6155,17 +6159,24 @@ plan_cluster_use_sort(Oid tableOid, Oid indexOid)
 /*
  * get_partitioned_child_rels
  *		Returns a list of the RT indexes of the partitioned child relations
- *		with rti as the root parent RT index.
+ *		with rti as the root parent RT index. Also sets
+ *		*part_cols_updated to true if any of the root rte's updated
+ *		columns is used in the partition key either of the relation whose RTI
+ *		is specified or of any child relation.
  *
  * Note: This function might get called even for range table entries that
  * are not partitioned tables; in such a case, it will simply return NIL.
  */
 List *
-get_partitioned_child_rels(PlannerInfo *root, Index rti)
+get_partitioned_child_rels(PlannerInfo *root, Index rti,
+						   bool *part_cols_updated)
 {
 	List	   *result = NIL;
 	ListCell   *l;
 
+	if (part_cols_updated)
+		*part_cols_updated = false;
+
 	foreach(l, root->pcinfo_list)
 	{
 		PartitionedChildRelInfo *pc = lfirst_node(PartitionedChildRelInfo, l);
@@ -6173,6 +6184,8 @@ get_partitioned_child_rels(PlannerInfo *root, Index rti)
 		if (pc->parent_relid == rti)
 		{
 			result = pc->child_rels;
+			if (part_cols_updated)
+				*part_cols_updated = pc->part_cols_updated;
 			break;
 		}
 	}