reclassify clumped joins as scans

7 files changed, 102 insertions, 119 deletions

diff --git a/contrib/pg_plan_advice/Makefile b/contrib/pg_plan_advice/Makefile
index afeea2e5dd..6f8127e551 100644
--- a/contrib/pg_plan_advice/Makefile
+++ b/contrib/pg_plan_advice/Makefile
@@ -8,6 +8,7 @@ OBJS = \
 	pgpa_identifier.o \
 	pgpa_join.o \
 	pgpa_output.o \
+	pgpa_scan.o \
 	pgpa_walker.o
 
 EXTENSION = pg_plan_advice
diff --git a/contrib/pg_plan_advice/meson.build b/contrib/pg_plan_advice/meson.build
index db510082d6..d9e3ec148c 100644
--- a/contrib/pg_plan_advice/meson.build
+++ b/contrib/pg_plan_advice/meson.build
@@ -6,6 +6,7 @@ pg_plan_advice_sources = files(
   'pgpa_identifier.c',
   'pgpa_join.c',
   'pgpa_output.c',
+  'pgpa_scan.c',
   'pgpa_walker.c',
 )
 
diff --git a/contrib/pg_plan_advice/pgpa_join.c b/contrib/pg_plan_advice/pgpa_join.c
index 64f8dfdb8a..392eea4dd2 100644
--- a/contrib/pg_plan_advice/pgpa_join.c
+++ b/contrib/pg_plan_advice/pgpa_join.c
@@ -1,6 +1,6 @@
 /*-------------------------------------------------------------------------
  *
- * pgpa_join.h
+ * pgpa_join.c
  *	  analysis of joins in Plan trees
  *
  * Copyright (c) 2016-2025, PostgreSQL Global Development Group
@@ -13,6 +13,7 @@
 #include "postgres.h"
 
 #include "pgpa_join.h"
+#include "pgpa_scan.h"
 #include "pgpa_walker.h"
 
 #include "nodes/pathnodes.h"
@@ -77,82 +78,6 @@ pgpa_get_join_class(Plan *plan)
 }
 
 /*
- * Build a pgpa_clumped_join object for a Plan node.
- *
- * If there is at least one ElidedNode for this plan node, pass the uppermost
- * one as elided_node, else pass NULL.
- */
-pgpa_clumped_join *
-pgpa_build_clumped_join(PlannedStmt *pstmt, Plan *plan,
-						ElidedNode *elided_node)
-{
-	pgpa_clumped_join *clump = palloc(sizeof(pgpa_clumped_join));
-	Bitmapset *relids = NULL;
-	int rti = -1;
-
-	clump->plan = plan;
-
-	if (elided_node != NULL)
-	{
-		NodeTag		elided_type = elided_node->elided_type;
-
-		/*
-		 * The only case we expect to encounter here is a partitionwise join
-		 * whose Append or MergeAppend node was elided due to having only one
-		 * surviving child. It's also possiblee for a trivial SubqueryScan to
-		 * be elided, but in that case we expected only a single RTI, in which
-		 * case it's not a join.
-		 */
-		Assert(bms_membership(elided_node->relids) == BMS_MULTIPLE);
-		relids = elided_node->relids;
-		if (elided_type == T_Append || elided_type == T_MergeAppend)
-			clump->strategy = JSTRAT_CLUMP_PARTITIONWISE;
-		else
-			elog(ERROR, "unexpected elided node type");
-	}
-	else
-	{
-		Assert(pgpa_get_join_class(plan) == PGPA_CLUMPED_JOIN);
-
-		relids = pgpa_relids(plan);
-
-		if (IsA(plan, Result))
-			clump->strategy = JSTRAT_CLUMP_DEGENERATE;
-		else if (IsA(plan, ForeignScan))
-			clump->strategy = JSTRAT_CLUMP_FOREIGN;
-		else if (IsA(plan, Append))
-			clump->strategy = JSTRAT_CLUMP_PARTITIONWISE;
-		else if (IsA(plan, MergeAppend))
-			clump->strategy = JSTRAT_CLUMP_PARTITIONWISE;
-		else
-			elog(ERROR, "unexpected plan type");
-	}
-
-	/*
-	 * Filter out any RTIs of type RTE_JOIN, since we have no use for them,
-	 * and don't want them creating confusion later. (We always refer to
-	 * groups of relations in terms of the relation RTIs, not the join RTIs.)
-	 */
-	clump->relids = NULL;
-	while ((rti = bms_next_member(relids, rti)) >= 0)
-	{
-		RangeTblEntry *rte = rt_fetch(rti, pstmt->rtable);
-
-		if (rte->rtekind != RTE_JOIN)
-			clump->relids = bms_add_member(clump->relids, rti);
-	}
-
-	/*
-	 * We concluded that this was a join based on the fact that there were
-	 * multiple RTIs -- and even after removing the join RTIs, that should
-	 * still be the case.
-	 */
-	Assert(bms_membership(clump->relids) == BMS_MULTIPLE);
-
-	return clump;
-}
-
-/*
  * Create an initially-empty object for unrolling joins.
  *
  * See comments for pgpa_unrolled_join and pgpa_clumped_join in pgpa_join.h
diff --git a/contrib/pg_plan_advice/pgpa_join.h b/contrib/pg_plan_advice/pgpa_join.h
index 3a8585c616..e7dabbae2f 100644
--- a/contrib/pg_plan_advice/pgpa_join.h
+++ b/contrib/pg_plan_advice/pgpa_join.h
@@ -15,48 +15,11 @@
 #include "nodes/plannodes.h"
 
 struct pgpa_plan_walker_context;
+struct pgpa_clumped_join;
 typedef struct pgpa_join_unroller pgpa_join_unroller;
 typedef struct pgpa_unrolled_join pgpa_unrolled_join;
 
 /*
- * Certain types of plan nodes can join any number of input relations in
- * a single step; we call these "clumped joins".
- *
- * For our purposes, the important thing about a clumped join is that we
- * can't meaningfully speak about the order in which tables are joined
- * within a single clump. For example, if the optimizer chooses a
- * partitionwise join on tables A and B, we can't say whether A was joined
- * to B or whether B was joined to A; instead, each pair of child tables
- * has its own join order. Likewise, if a foreign data wrapper pushes a
- * join to the remote side, we don't know the join order.
- *
- * JSTRAT_CLUMP_DEGENERATE refers to the case where several relations are
- * all proven empty and replaced with a single Result node. Here again, while
- * the Result node may be joined to other things and we can speak about its
- * place within the larger join order, we can't speak about a join ordering
- * within the Result node itself.
- */
-typedef enum
-{
-	JSTRAT_CLUMP_DEGENERATE = 0,
-	JSTRAT_CLUMP_FOREIGN,
-	JSTRAT_CLUMP_PARTITIONWISE
-	/* update NUM_PGPA_CLUMP_JOIN_STRATEGY if you add anything here */
-} pgpa_join_clump_strategy;
-
-#define NUM_PGPA_CLUMP_JOIN_STRATEGY	((int) JSTRAT_CLUMP_PARTITIONWISE + 1)
-
-/*
- * All of the details we need regarding a clumped join.
- */
-typedef struct
-{
-	Plan	   *plan;
-	pgpa_join_clump_strategy strategy;
-	Bitmapset  *relids;
-} pgpa_clumped_join;
-
-/*
  * Although there are three main join strategies, we try to classify things
  * more precisely here: merge joins have the option of using materialization
  * on the inner side, and nested loops can use either materialization or
@@ -97,7 +60,7 @@ typedef struct
 	Plan	   *plan;
 	ElidedNode *elided_node;
 	Index		rti;
-	pgpa_clumped_join *clump_join;
+	struct pgpa_clumped_join *clump_join;
 	pgpa_unrolled_join *unrolled_join;
 } pgpa_join_member;
 
@@ -135,9 +98,6 @@ typedef enum
 } pgpa_join_class;
 
 extern pgpa_join_class pgpa_get_join_class(Plan *plan);
-extern pgpa_clumped_join *pgpa_build_clumped_join(PlannedStmt *pstmt,
-												  Plan *plan,
-												  ElidedNode *elided_node);
 
 extern pgpa_join_unroller *pgpa_create_join_unroller(void);
 extern void pgpa_unroll_join(struct pgpa_plan_walker_context *walker,
diff --git a/contrib/pg_plan_advice/pgpa_output.c b/contrib/pg_plan_advice/pgpa_output.c
index 4fe3890381..634cd75af5 100644
--- a/contrib/pg_plan_advice/pgpa_output.c
+++ b/contrib/pg_plan_advice/pgpa_output.c
@@ -13,6 +13,7 @@
 #include "postgres.h"
 
 #include "pgpa_output.h"
+#include "pgpa_scan.h"
 
 typedef struct pgpa_output_context
 {
diff --git a/contrib/pg_plan_advice/pgpa_scan.c b/contrib/pg_plan_advice/pgpa_scan.c
new file mode 100644
index 0000000000..41686dd704
--- /dev/null
+++ b/contrib/pg_plan_advice/pgpa_scan.c
@@ -0,0 +1,94 @@
+/*-------------------------------------------------------------------------
+ *
+ * pgpa_scan.c
+ *	  analysis of scans in Plan trees
+ *
+ * Copyright (c) 2016-2025, PostgreSQL Global Development Group
+ *
+ *	  contrib/pg_plan_advice/pgpa_scan.c
+ *
+ *-------------------------------------------------------------------------
+ */
+#include "postgres.h"
+
+#include "pgpa_scan.h"
+#include "pgpa_walker.h"
+
+#include "nodes/parsenodes.h"
+#include "parser/parsetree.h"
+
+/*
+ * Build a pgpa_clumped_join object for a Plan node.
+ *
+ * If there is at least one ElidedNode for this plan node, pass the uppermost
+ * one as elided_node, else pass NULL.
+ */
+pgpa_clumped_join *
+pgpa_build_clumped_join(PlannedStmt *pstmt, Plan *plan,
+						ElidedNode *elided_node)
+{
+	pgpa_clumped_join *clump = palloc(sizeof(pgpa_clumped_join));
+	Bitmapset *relids = NULL;
+	int rti = -1;
+
+	clump->plan = plan;
+
+	if (elided_node != NULL)
+	{
+		NodeTag		elided_type = elided_node->elided_type;
+
+		/*
+		 * The only case we expect to encounter here is a partitionwise join
+		 * whose Append or MergeAppend node was elided due to having only one
+		 * surviving child. It's also possiblee for a trivial SubqueryScan to
+		 * be elided, but in that case we expected only a single RTI, in which
+		 * case it's not a join.
+		 */
+		Assert(bms_membership(elided_node->relids) == BMS_MULTIPLE);
+		relids = elided_node->relids;
+		if (elided_type == T_Append || elided_type == T_MergeAppend)
+			clump->strategy = JSTRAT_CLUMP_PARTITIONWISE;
+		else
+			elog(ERROR, "unexpected elided node type");
+	}
+	else
+	{
+		Assert(pgpa_get_join_class(plan) == PGPA_CLUMPED_JOIN);
+
+		relids = pgpa_relids(plan);
+
+		if (IsA(plan, Result))
+			clump->strategy = JSTRAT_CLUMP_DEGENERATE;
+		else if (IsA(plan, ForeignScan))
+			clump->strategy = JSTRAT_CLUMP_FOREIGN;
+		else if (IsA(plan, Append))
+			clump->strategy = JSTRAT_CLUMP_PARTITIONWISE;
+		else if (IsA(plan, MergeAppend))
+			clump->strategy = JSTRAT_CLUMP_PARTITIONWISE;
+		else
+			elog(ERROR, "unexpected plan type");
+	}
+
+	/*
+	 * Filter out any RTIs of type RTE_JOIN, since we have no use for them,
+	 * and don't want them creating confusion later. (We always refer to
+	 * groups of relations in terms of the relation RTIs, not the join RTIs.)
+	 */
+	clump->relids = NULL;
+	while ((rti = bms_next_member(relids, rti)) >= 0)
+	{
+		RangeTblEntry *rte = rt_fetch(rti, pstmt->rtable);
+
+		if (rte->rtekind != RTE_JOIN)
+			clump->relids = bms_add_member(clump->relids, rti);
+	}
+
+	/*
+	 * We concluded that this was a join based on the fact that there were
+	 * multiple RTIs -- and even after removing the join RTIs, that should
+	 * still be the case.
+	 */
+	Assert(bms_membership(clump->relids) == BMS_MULTIPLE);
+
+	return clump;
+}
diff --git a/contrib/pg_plan_advice/pgpa_walker.c b/contrib/pg_plan_advice/pgpa_walker.c
index 8973180379..3d20d6cc05 100644
--- a/contrib/pg_plan_advice/pgpa_walker.c
+++ b/contrib/pg_plan_advice/pgpa_walker.c
@@ -1,6 +1,7 @@
 #include "postgres.h"
 
 #include "pgpa_join.h"
+#include "pgpa_scan.h"
 #include "pgpa_walker.h"
 
 #include "nodes/plannodes.h"