Initial code review for CustomScan patch.

Get rid of the pernicious entanglement between planner and executor headers
introduced by commit 0b03e595.

Also, rearrange the CustomFoo struct/typedef definitions so that all the
typedef names are seen as used by the compiler.  Without this pgindent
will mess things up a bit, which is not so important perhaps, but it also
removes a bizarre discrepancy between the declaration arrangement used for
CustomExecMethods and that used for CustomScanMethods and
CustomPathMethods.

Clean up the commentary around ExecSupportsMarkRestore to reflect the
rather large change in its API.

Const-ify register_custom_path_provider's argument.  This necessitates
casting away const in the function, but that seems better than forcing
callers of the function to do so (or else not const-ify their method
pointer structs, which was sort of the whole point).

De-export fix_expr_common.  I don't like the exporting of fix_scan_expr
or replace_nestloop_params either, but this one surely has got little
excuse.

src/backend/executor/execAmi.c

@@ -381,11 +381,14 @@ ExecRestrPos(PlanState *node)
 }
 
 /*
- * ExecSupportsMarkRestore - does a plan type support mark/restore?
+ * ExecSupportsMarkRestore - does a Path support mark/restore?
+ *
+ * This is used during planning and so must accept a Path, not a Plan.
+ * We keep it here to be adjacent to the routines above, which also must
+ * know which plan types support mark/restore.
  *
  * XXX Ideally, all plan node types would support mark/restore, and this
  * wouldn't be needed.  For now, this had better match the routines above.
- * But note the test is on Plan nodetype, not PlanState nodetype.
  *
  * (However, since the only present use of mark/restore is in mergejoin,
  * there is no need to support mark/restore in any plan type that is not
@@ -395,6 +398,11 @@ ExecRestrPos(PlanState *node)
 bool
 ExecSupportsMarkRestore(Path *pathnode)
 {
+	/*
+	 * For consistency with the routines above, we do not examine the nodeTag
+	 * but rather the pathtype, which is the Plan node type the Path would
+	 * produce.
+	 */
 	switch (pathnode->pathtype)
 	{
 		case T_SeqScan:
@@ -406,27 +414,23 @@ ExecSupportsMarkRestore(Path *pathnode)
 		case T_Sort:
 			return true;
 
+		case T_CustomScan:
+			Assert(IsA(pathnode, CustomPath));
+			if (((CustomPath *) pathnode)->flags & CUSTOMPATH_SUPPORT_MARK_RESTORE)
+				return true;
+			return false;
+
 		case T_Result:
 
 			/*
-			 * T_Result only supports mark/restore if it has a child plan that
-			 * does, so we do not have enough information to give a really
-			 * correct answer.  However, for current uses it's enough to
-			 * always say "false", because this routine is not asked about
-			 * gating Result plans, only base-case Results.
+			 * Although Result supports mark/restore if it has a child plan
+			 * that does, we presently come here only for ResultPath nodes,
+			 * which represent Result plans without a child plan.  So there is
+			 * nothing to recurse to and we can just say "false".
 			 */
+			Assert(IsA(pathnode, ResultPath));
 			return false;
 
-		case T_CustomScan:
-			{
-				CustomPath *cpath = (CustomPath *) pathnode;
-
-				Assert(IsA(cpath, CustomPath));
-				if (cpath->flags & CUSTOMPATH_SUPPORT_MARK_RESTORE)
-					return true;
-			}
-			break;
-
 		default:
 			break;
 	}
@@ -493,8 +497,8 @@ ExecSupportsBackwardScan(Plan *node)
 			{
 				uint32		flags = ((CustomScan *) node)->flags;
 
-				if (TargetListSupportsBackwardScan(node->targetlist) &&
-					(flags & CUSTOMPATH_SUPPORT_BACKWARD_SCAN) != 0)
+				if ((flags & CUSTOMPATH_SUPPORT_BACKWARD_SCAN) &&
+					TargetListSupportsBackwardScan(node->targetlist))
 					return true;
 			}
 			return false;

src/backend/optimizer/plan/createplan.c

@@ -1083,52 +1083,6 @@ create_unique_plan(PlannerInfo *root, UniquePath *best_path)
 	return plan;
 }
 
-/*
- * create_custom_plan
- *
- * Transform a CustomPath into a Plan.
- */
-static Plan *
-create_customscan_plan(PlannerInfo *root, CustomPath *best_path,
-					   List *tlist, List *scan_clauses)
-{
-	Plan		   *plan;
-	RelOptInfo	   *rel = best_path->path.parent;
-
-	/*
-	 * Right now, all we can support is CustomScan node which is associated
-	 * with a particular base relation to be scanned.
-	 */
-	Assert(rel && rel->reloptkind == RELOPT_BASEREL);
-
-	/*
-	 * Sort clauses into the best execution order, although custom-scan
-	 * provider can reorder them again.
-	 */
-	scan_clauses = order_qual_clauses(root, scan_clauses);
-
-	/*
-	 * Create a CustomScan (or its inheritance) node according to
-	 * the supplied CustomPath.
-	 */
-	plan = best_path->methods->PlanCustomPath(root, rel, best_path, tlist,
-											  scan_clauses);
-
-	/*
-	 * NOTE: unlike create_foreignscan_plan(), it is responsibility of
-	 * the custom plan provider to replace outer-relation variables
-	 * with nestloop params, because we cannot know how many expression
-	 * trees are held in the private fields.
-	 */
-
-	/*
-	 * Copy cost data from Path to Plan; no need to make custom-plan
-	 * providers do this
-	 */
-	copy_path_costsize(plan, &best_path->path);
-
-	return plan;
-}
 
 /*****************************************************************************
  *
@@ -2063,6 +2017,53 @@ create_foreignscan_plan(PlannerInfo *root, ForeignPath *best_path,
 	return scan_plan;
 }
 
+/*
+ * create_custom_plan
+ *
+ * Transform a CustomPath into a Plan.
+ */
+static Plan *
+create_customscan_plan(PlannerInfo *root, CustomPath *best_path,
+					   List *tlist, List *scan_clauses)
+{
+	Plan	   *plan;
+	RelOptInfo *rel = best_path->path.parent;
+
+	/*
+	 * Right now, all we can support is CustomScan node which is associated
+	 * with a particular base relation to be scanned.
+	 */
+	Assert(rel && rel->reloptkind == RELOPT_BASEREL);
+
+	/*
+	 * Sort clauses into the best execution order, although custom-scan
+	 * provider can reorder them again.
+	 */
+	scan_clauses = order_qual_clauses(root, scan_clauses);
+
+	/*
+	 * Invoke custom plan provider to create the Plan node represented by the
+	 * CustomPath.
+	 */
+	plan = best_path->methods->PlanCustomPath(root, rel, best_path, tlist,
+											  scan_clauses);
+
+	/*
+	 * NOTE: unlike create_foreignscan_plan(), it is the responsibility of the
+	 * custom plan provider to replace outer-relation variables with nestloop
+	 * params, because we cannot know what expression trees may be held in
+	 * private fields.
+	 */
+
+	/*
+	 * Copy cost data from Path to Plan; no need to make custom-plan providers
+	 * do this
+	 */
+	copy_path_costsize(plan, &best_path->path);
+
+	return plan;
+}
+
 
 /*****************************************************************************
  *

src/backend/optimizer/plan/setrefs.c

@@ -587,12 +587,13 @@ set_plan_refs(PlannerInfo *root, Plan *plan, int rtoffset)
 					fix_scan_list(root, cscan->scan.plan.targetlist, rtoffset);
 				cscan->scan.plan.qual =
 					fix_scan_list(root, cscan->scan.plan.qual, rtoffset);
+
 				/*
-				 * The core implementation applies the routine to fixup
-				 * varno on the target-list and scan qualifier.
-				 * If custom-scan has additional expression nodes on its
-				 * private fields, it has to apply same fixup on them.
-				 * Otherwise, the custom-plan provider can skip this callback.
+				 * The core implementation applies the routine to fixup varno
+				 * on the target-list and scan qualifier. If custom-scan has
+				 * additional expression nodes on its private fields, it has
+				 * to apply same fixup on them. Otherwise, the custom-plan
+				 * provider can skip this callback.
 				 */
 				if (cscan->methods->SetCustomScanRef)
 					cscan->methods->SetCustomScanRef(root, cscan, rtoffset);
@@ -1083,7 +1084,7 @@ copyVar(Var *var)
  * We assume it's okay to update opcode info in-place.  So this could possibly
  * scribble on the planner's input data structures, but it's OK.
  */
-void
+static void
 fix_expr_common(PlannerInfo *root, Node *node)
 {
 	/* We assume callers won't call us on a NULL pointer */

src/backend/optimizer/util/pathnode.c

@@ -1942,12 +1942,13 @@ static List	   *custom_path_providers = NIL;
  * methods of scanning a relation.
  */
 void
-register_custom_path_provider(CustomPathMethods *cpp_methods)
+register_custom_path_provider(const CustomPathMethods *cpp_methods)
 {
 	MemoryContext oldcxt;
 
 	oldcxt = MemoryContextSwitchTo(TopMemoryContext);
-	custom_path_providers = lappend(custom_path_providers, cpp_methods);
+	custom_path_providers = lappend(custom_path_providers,
+									(void *) cpp_methods);
 	MemoryContextSwitchTo(oldcxt);
 }
 
@@ -1965,7 +1966,7 @@ create_customscan_paths(PlannerInfo *root,
 {
 	ListCell   *cell;
 
-	foreach (cell, custom_path_providers)
+	foreach(cell, custom_path_providers)
 	{
 		const CustomPathMethods *cpp_methods = lfirst(cell);
 

src/include/executor/executor.h

@@ -16,7 +16,6 @@
 
 #include "executor/execdesc.h"
 #include "nodes/parsenodes.h"
-#include "nodes/relation.h"
 #include "utils/lockwaitpolicy.h"
 
 
@@ -101,10 +100,12 @@ extern PGDLLIMPORT ExecutorCheckPerms_hook_type ExecutorCheckPerms_hook;
 /*
  * prototypes from functions in execAmi.c
  */
+struct Path;					/* avoid including relation.h here */
+
 extern void ExecReScan(PlanState *node);
 extern void ExecMarkPos(PlanState *node);
 extern void ExecRestrPos(PlanState *node);
-extern bool ExecSupportsMarkRestore(Path *pathnode);
+extern bool ExecSupportsMarkRestore(struct Path *pathnode);
 extern bool ExecSupportsBackwardScan(Plan *node);
 extern bool ExecMaterializesOutput(NodeTag plantype);
 

src/include/executor/nodeCustom.h

@@ -11,7 +11,7 @@
  */
 #ifndef NODECUSTOM_H
 #define NODECUSTOM_H
-#include "nodes/plannodes.h"
+
 #include "nodes/execnodes.h"
 
 /*

src/include/nodes/execnodes.h

@@ -19,7 +19,6 @@
 #include "executor/instrument.h"
 #include "nodes/params.h"
 #include "nodes/plannodes.h"
-#include "nodes/relation.h"
 #include "utils/reltrigger.h"
 #include "utils/sortsupport.h"
 #include "utils/tuplestore.h"
@@ -1512,39 +1511,39 @@ typedef struct ForeignScanState
  *		CustomScan nodes are used to execute custom code within executor.
  * ----------------
  */
-struct CustomExecMethods;
-struct ExplainState;	/* to avoid to include explain.h here */
-
-typedef struct CustomScanState
-{
-	ScanState	ss;
-	uint32		flags;	/* mask of CUSTOMPATH_* flags defined in relation.h*/
-	const struct CustomExecMethods *methods;
-} CustomScanState;
+struct ExplainState;			/* avoid including explain.h here */
+struct CustomScanState;
 
 typedef struct CustomExecMethods
 {
 	const char *CustomName;
 
 	/* EXECUTOR methods */
-	void    (*BeginCustomScan)(CustomScanState *node,
+	void		(*BeginCustomScan) (struct CustomScanState *node,
 												EState *estate,
 												int eflags);
-	TupleTableSlot *(*ExecCustomScan)(CustomScanState *node);
-	void	(*EndCustomScan)(CustomScanState *node);
-	void	(*ReScanCustomScan)(CustomScanState *node);
-	void	(*MarkPosCustomScan)(CustomScanState *node);
-	void	(*RestrPosCustomScan)(CustomScanState *node);
+	TupleTableSlot *(*ExecCustomScan) (struct CustomScanState *node);
+	void		(*EndCustomScan) (struct CustomScanState *node);
+	void		(*ReScanCustomScan) (struct CustomScanState *node);
+	void		(*MarkPosCustomScan) (struct CustomScanState *node);
+	void		(*RestrPosCustomScan) (struct CustomScanState *node);
 
 	/* EXPLAIN support */
-	void    (*ExplainCustomScan)(CustomScanState *node,
+	void		(*ExplainCustomScan) (struct CustomScanState *node,
 												  List *ancestors,
 												  struct ExplainState *es);
-	Node   *(*GetSpecialCustomVar)(CustomScanState *node,
+	Node	   *(*GetSpecialCustomVar) (struct CustomScanState *node,
 													Var *varnode,
 													PlanState **child_ps);
 } CustomExecMethods;
 
+typedef struct CustomScanState
+{
+	ScanState	ss;
+	uint32		flags;			/* mask of CUSTOMPATH_* flags, see relation.h */
+	const CustomExecMethods *methods;
+} CustomScanState;
+
 /* ----------------------------------------------------------------
  *				 Join State Information
  * ----------------------------------------------------------------

src/include/nodes/plannodes.h

@@ -18,7 +18,6 @@
 #include "lib/stringinfo.h"
 #include "nodes/bitmapset.h"
 #include "nodes/primnodes.h"
-#include "nodes/relation.h"
 #include "utils/lockwaitpolicy.h"
 
 
@@ -489,30 +488,33 @@ typedef struct ForeignScan
  *	   CustomScan node
  * ----------------
  */
-struct CustomScanMethods;
-
-typedef struct CustomScan
-{
-	Scan		scan;
-	uint32		flags;	/* mask of CUSTOMPATH_* flags defined in relation.h */
-	struct CustomScanMethods *methods;
-} CustomScan;
+struct PlannerInfo;				/* avoid including relation.h here */
+struct CustomScan;
 
 typedef struct CustomScanMethods
 {
 	const char *CustomName;
-	void	   (*SetCustomScanRef)(struct PlannerInfo *root,
-								   CustomScan *cscan,
+
+	void		(*SetCustomScanRef) (struct PlannerInfo *root,
+												 struct CustomScan *cscan,
 												 int rtoffset);
-	void	   (*FinalizeCustomScan)(struct PlannerInfo *root,
-									 CustomScan *cscan,
-									 bool (*finalize_primnode)(),
+	void		(*FinalizeCustomScan) (struct PlannerInfo *root,
+												   struct CustomScan *cscan,
+												bool (*finalize_primnode) (),
 												   void *finalize_context);
-	Node	  *(*CreateCustomScanState)(CustomScan *cscan);
-	void	   (*TextOutCustomScan)(StringInfo str, const CustomScan *node);
-	CustomScan *(*CopyCustomScan)(const CustomScan *from);
+	Node	   *(*CreateCustomScanState) (struct CustomScan *cscan);
+	void		(*TextOutCustomScan) (StringInfo str,
+											  const struct CustomScan *node);
+	struct CustomScan *(*CopyCustomScan) (const struct CustomScan *from);
 } CustomScanMethods;
 
+typedef struct CustomScan
+{
+	Scan		scan;
+	uint32		flags;			/* mask of CUSTOMPATH_* flags, see relation.h */
+	const CustomScanMethods *methods;
+} CustomScan;
+
 /*
  * ==========
  * Join nodes

src/include/nodes/relation.h

@@ -897,34 +897,34 @@ typedef struct ForeignPath
  * the structure declared here; providers are expected to make it the first
  * element in a larger structure.
  */
-
-struct CustomPathMethods;
-struct Plan;		/* not to include plannodes.h here */
+struct CustomPath;
 
 #define CUSTOMPATH_SUPPORT_BACKWARD_SCAN	0x0001
 #define CUSTOMPATH_SUPPORT_MARK_RESTORE		0x0002
 
-typedef struct CustomPath
-{
-	Path        path;
-	uint32		flags;
-	const struct CustomPathMethods *methods;
-} CustomPath;
-
 typedef struct CustomPathMethods
 {
 	const char *CustomName;
-	void	(*CreateCustomScanPath)(PlannerInfo *root,
+
+	void		(*CreateCustomScanPath) (PlannerInfo *root,
 													 RelOptInfo *baserel,
 													 RangeTblEntry *rte);
-	struct Plan	*(*PlanCustomPath)(PlannerInfo *root,
+	struct Plan *(*PlanCustomPath) (PlannerInfo *root,
 												RelOptInfo *rel,
-								   CustomPath *best_path,
+												struct CustomPath *best_path,
 												List *tlist,
 												List *clauses);
-	void    (*TextOutCustomPath)(StringInfo str, const CustomPath *node);
+	void		(*TextOutCustomPath) (StringInfo str,
+											  const struct CustomPath *node);
 } CustomPathMethods;
 
+typedef struct CustomPath
+{
+	Path		path;
+	uint32		flags;			/* mask of CUSTOMPATH_* flags, see above */
+	const CustomPathMethods *methods;
+} CustomPath;
+
 /*
  * AppendPath represents an Append plan, ie, successive execution of
  * several member plans.

src/include/optimizer/pathnode.h

@@ -131,7 +131,7 @@ extern Path *reparameterize_path(PlannerInfo *root, Path *path,
 /*
  * Interface definition of custom-scan providers
  */
-extern void register_custom_path_provider(CustomPathMethods *cpp_methods);
+extern void register_custom_path_provider(const CustomPathMethods *cpp_methods);
 
 extern void create_customscan_paths(PlannerInfo *root,
 						RelOptInfo *baserel,

src/include/optimizer/planmain.h

@@ -130,9 +130,8 @@ extern bool query_is_distinct_for(Query *query, List *colnos, List *opids);
  * prototypes for plan/setrefs.c
  */
 extern Plan *set_plan_references(PlannerInfo *root, Plan *plan);
-extern void fix_opfuncids(Node *node);
 extern Node *fix_scan_expr(PlannerInfo *root, Node *node, int rtoffset);
-extern void fix_expr_common(PlannerInfo *root, Node *node);
+extern void fix_opfuncids(Node *node);
 extern void set_opfuncid(OpExpr *opexpr);
 extern void set_sa_opfuncid(ScalarArrayOpExpr *opexpr);
 extern void record_plan_function_dependency(PlannerInfo *root, Oid funcid);