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, 29 insertions, 5 deletions

diff --git a/src/include/executor/execPartition.h b/src/include/executor/execPartition.h
index b5df357acdf..18e08129f84 100644
--- a/src/include/executor/execPartition.h
+++ b/src/include/executor/execPartition.h
@@ -62,11 +62,24 @@ typedef struct PartitionDispatchData *PartitionDispatch;
  *								for every leaf partition in the partition tree.
  * num_partitions				Number of leaf partitions in the partition tree
  *								(= 'partitions' array length)
- * partition_tupconv_maps		Array of TupleConversionMap objects with one
+ * parent_child_tupconv_maps	Array of TupleConversionMap objects with one
  *								entry for every leaf partition (required to
- *								convert input tuple based on the root table's
- *								rowtype to a leaf partition's rowtype after
- *								tuple routing is done)
+ *								convert tuple from the root table's rowtype to
+ *								a leaf partition's rowtype after tuple routing
+ *								is done)
+ * child_parent_tupconv_maps	Array of TupleConversionMap objects with one
+ *								entry for every leaf partition (required to
+ *								convert an updated tuple from the leaf
+ *								partition's rowtype to the root table's rowtype
+ *								so that tuple routing can be done)
+ * child_parent_map_not_required  Array of bool. True value means that a map is
+ *								determined to be not required for the given
+ *								partition. False means either we haven't yet
+ *								checked if a map is required, or it was
+ *								determined to be required.
+ * subplan_partition_offsets	Integer array ordered by UPDATE subplans. Each
+ *								element of this array has the index into the
+ *								corresponding partition in partitions array.
  * partition_tuple_slot			TupleTableSlot to be used to manipulate any
  *								given leaf partition's rowtype after that
  *								partition is chosen for insertion by
@@ -79,8 +92,12 @@ typedef struct PartitionTupleRouting
 	int			num_dispatch;
 	ResultRelInfo **partitions;
 	int			num_partitions;
-	TupleConversionMap **partition_tupconv_maps;
+	TupleConversionMap **parent_child_tupconv_maps;
+	TupleConversionMap **child_parent_tupconv_maps;
+	bool	   *child_parent_map_not_required;
+	int		   *subplan_partition_offsets;
 	TupleTableSlot *partition_tuple_slot;
+	TupleTableSlot *root_tuple_slot;
 } PartitionTupleRouting;
 
 extern PartitionTupleRouting *ExecSetupPartitionTupleRouting(ModifyTableState *mtstate,
@@ -90,6 +107,13 @@ extern int ExecFindPartition(ResultRelInfo *resultRelInfo,
 				  PartitionDispatch *pd,
 				  TupleTableSlot *slot,
 				  EState *estate);
+extern void ExecSetupChildParentMapForLeaf(PartitionTupleRouting *proute);
+extern TupleConversionMap *TupConvMapForLeaf(PartitionTupleRouting *proute,
+				  ResultRelInfo *rootRelInfo, int leaf_index);
+extern HeapTuple ConvertPartitionTupleSlot(TupleConversionMap *map,
+						  HeapTuple tuple,
+						  TupleTableSlot *new_slot,
+						  TupleTableSlot **p_my_slot);
 extern void ExecCleanupTupleRouting(PartitionTupleRouting *proute);
 
 #endif							/* EXECPARTITION_H */