Remove some unnecessary fields from Plan trees.

In the wake of commit f2343653f, we no longer need some fields that
were used before to control executor lock acquisitions:

* PlannedStmt.nonleafResultRelations can go away entirely.

* partitioned_rels can go away from Append, MergeAppend, and ModifyTable.
However, ModifyTable still needs to know the RT index of the partition
root table if any, which was formerly kept in the first entry of that
list.  Add a new field "rootRelation" to remember that.  rootRelation is
partly redundant with nominalRelation, in that if it's set it will have
the same value as nominalRelation.  However, the latter field has a
different purpose so it seems best to keep them distinct.

Amit Langote, reviewed by David Rowley and Jesper Pedersen,
and whacked around a bit more by me

Discussion: https://postgr.es/m/468c85d9-540e-66a2-1dde-fec2b741e688@lab.ntt.co.jp

3 files changed, 12 insertions, 21 deletions

diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 8b374370576..5e3d4cdc58d 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -69,15 +69,8 @@ typedef struct PlannedStmt
 	List	   *resultRelations;	/* integer list of RT indexes, or NIL */
 
 	/*
-	 * rtable indexes of non-leaf target relations for UPDATE/DELETE on all
-	 * the partitioned tables mentioned in the query.
-	 */
-	List	   *nonleafResultRelations;
-
-	/*
-	 * rtable indexes of root target relations for UPDATE/DELETE; this list
-	 * maintains a subset of the RT indexes in nonleafResultRelations,
-	 * indicating the roots of the respective partition hierarchies.
+	 * rtable indexes of partitioned table roots that are UPDATE/DELETE
+	 * targets; needed for trigger firing.
 	 */
 	List	   *rootResultRelations;
 
@@ -210,6 +203,12 @@ typedef struct ProjectSet
  *		Apply rows produced by subplan(s) to result table(s),
  *		by inserting, updating, or deleting.
  *
+ * If the originally named target table is a partitioned table, both
+ * nominalRelation and rootRelation contain the RT index of the partition
+ * root, which is not otherwise mentioned in the plan.  Otherwise rootRelation
+ * is zero.  However, nominalRelation will always be set, as it's the rel that
+ * EXPLAIN should claim is the INSERT/UPDATE/DELETE target.
+ *
  * Note that rowMarks and epqParam are presumed to be valid for all the
  * subplan(s); they can't contain any info that varies across subplans.
  * ----------------
@@ -220,8 +219,7 @@ typedef struct ModifyTable
 	CmdType		operation;		/* INSERT, UPDATE, or DELETE */
 	bool		canSetTag;		/* do we set the command tag/es_processed? */
 	Index		nominalRelation;	/* Parent RT index for use of EXPLAIN */
-	/* RT indexes of non-leaf tables in a partition tree */
-	List	   *partitioned_rels;
+	Index		rootRelation;	/* Root RT index, if target is partitioned */
 	bool		partColsUpdated;	/* some part key in hierarchy updated */
 	List	   *resultRelations;	/* integer list of RT indexes */
 	int			resultRelIndex; /* index of first resultRel in plan's list */
@@ -259,9 +257,6 @@ typedef struct Append
 	 */
 	int			first_partial_plan;
 
-	/* RT indexes of non-leaf tables in a partition tree */
-	List	   *partitioned_rels;
-
 	/* Info for run-time subplan pruning; NULL if we're not doing that */
 	struct PartitionPruneInfo *part_prune_info;
 } Append;
@@ -274,10 +269,8 @@ typedef struct Append
 typedef struct MergeAppend
 {
 	Plan		plan;
-	/* RT indexes of non-leaf tables in a partition tree */
-	List	   *partitioned_rels;
 	List	   *mergeplans;
-	/* remaining fields are just like the sort-key info in struct Sort */
+	/* these fields are just like the sort-key info in struct Sort: */
 	int			numCols;		/* number of sort-key columns */
 	AttrNumber *sortColIdx;		/* their indexes in the target list */
 	Oid		   *sortOperators;	/* OIDs of operators to sort them by */
diff --git a/src/include/nodes/relation.h b/src/include/nodes/relation.h
index adb42650479..88d37236f7d 100644
--- a/src/include/nodes/relation.h
+++ b/src/include/nodes/relation.h
@@ -121,7 +121,6 @@ typedef struct PlannerGlobal
 
 	List	   *resultRelations;	/* "flat" list of integer RT indexes */
 
-	List	   *nonleafResultRelations; /* "flat" list of integer RT indexes */
 	List	   *rootResultRelations;	/* "flat" list of integer RT indexes */
 
 	List	   *relationOids;	/* OIDs of relations the plan depends on */
@@ -1717,8 +1716,7 @@ typedef struct ModifyTablePath
 	CmdType		operation;		/* INSERT, UPDATE, or DELETE */
 	bool		canSetTag;		/* do we set the command tag/es_processed? */
 	Index		nominalRelation;	/* Parent RT index for use of EXPLAIN */
-	/* RT indexes of non-leaf tables in a partition tree */
-	List	   *partitioned_rels;
+	Index		rootRelation;	/* Root RT index, if target is partitioned */
 	bool		partColsUpdated;	/* some part key in hierarchy updated */
 	List	   *resultRelations;	/* integer list of RT indexes */
 	List	   *subpaths;		/* Path(s) producing source data */
diff --git a/src/include/optimizer/pathnode.h b/src/include/optimizer/pathnode.h
index 7c5ff226501..81abcf53a83 100644
--- a/src/include/optimizer/pathnode.h
+++ b/src/include/optimizer/pathnode.h
@@ -238,7 +238,7 @@ extern LockRowsPath *create_lockrows_path(PlannerInfo *root, RelOptInfo *rel,
 extern ModifyTablePath *create_modifytable_path(PlannerInfo *root,
 						RelOptInfo *rel,
 						CmdType operation, bool canSetTag,
-						Index nominalRelation, List *partitioned_rels,
+						Index nominalRelation, Index rootRelation,
 						bool partColsUpdated,
 						List *resultRelations, List *subpaths,
 						List *subroots,