Showing applied extended statistics in explain Part 2

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index f1d71bc54e..622aad8394 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -78,6 +78,9 @@ static void show_qual(List *qual, const char *qlabel,
 static void show_scan_qual(List *qual, const char *qlabel,
 						   PlanState *planstate, List *ancestors,
 						   ExplainState *es);
+static void show_scan_stats(List *stats, List *clauses, List *ors,
+							PlanState *planstate, List *ancestors,
+							ExplainState *es);
 static void show_upper_qual(List *qual, const char *qlabel,
 							PlanState *planstate, List *ancestors,
 							ExplainState *es);
@@ -1795,6 +1798,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_IndexOnlyScan:
 			show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
@@ -1811,10 +1818,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (es->analyze)
 				ExplainPropertyFloat("Heap Fetches", NULL,
 									 planstate->instrument->ntuples2, 0, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapHeapScan:
 			show_scan_qual(((BitmapHeapScan *) plan)->bitmapqualorig,
@@ -1844,6 +1859,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Gather:
 			{
@@ -2031,6 +2050,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_WindowAgg:
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
@@ -2046,6 +2069,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Sort:
 			show_sort_keys(castNode(SortState, planstate), ancestors, es);
@@ -2365,6 +2392,76 @@ show_scan_qual(List *qual, const char *qlabel,
 	show_qual(qual, qlabel, planstate, ancestors, useprefix, es);
 }
 
+/*
+ * Show a generic expression
+ */
+static char *
+deparse_stat_expression(Node *node,
+						PlanState *planstate, List *ancestors,
+						ExplainState *es)
+{
+	List	   *context;
+
+	/* Set up deparsing context */
+	context = set_deparse_context_plan(es->deparse_cxt,
+									   planstate->plan,
+									   ancestors);
+
+	/* Deparse the expression */
+	return deparse_expression(node, context, false, false);
+}
+
+/*
+ * Show a qualifier expression (which is a List with implicit AND semantics)
+ */
+static char *
+show_stat_qual(List *qual, bool is_or,
+			   PlanState *planstate, List *ancestors,
+			   ExplainState *es)
+{
+	Node	   *node;
+
+	/* No work if empty qual */
+	if (qual == NIL)
+		return NULL;
+
+	/* Convert AND list to explicit AND */
+	if (is_or)
+		node = (Node *) make_ors_explicit(qual);
+	else
+		node = (Node *) make_ands_explicit(qual);
+
+	/* And show it */
+	return deparse_stat_expression(node, planstate, ancestors, es);
+}
+
+/*
+ * Show applied statistics for scan plan node
+ */
+static void
+show_scan_stats(List *stats, List *clauses, List *ors,
+				PlanState *planstate, List *ancestors, ExplainState *es)
+{
+	ListCell   *lc1, *lc2, *lc3;
+	StringInfoData	str;
+
+	forthree (lc1, stats, lc2, clauses, lc3, ors)
+	{
+		StatisticExtInfo   *stat = (StatisticExtInfo *) lfirst(lc1);
+		List   *applied_clauses = (List *) lfirst(lc2);
+		int		is_or = lfirst_int(lc3);
+
+		initStringInfo(&str);
+
+		appendStringInfo(&str, "%s.%s  Clauses: %s",
+						 get_namespace_name(get_statistics_namespace(stat->statOid)),
+						 get_statistics_name(stat->statOid),
+						 show_stat_qual(applied_clauses, is_or, planstate, ancestors, es));
+
+		ExplainPropertyText("Statistics", str.data, es);
+	}
+}
+
 /*
  * Show a qualifier expression for an upper-level plan node
  */
diff --git a/src/backend/nodes/makefuncs.c b/src/backend/nodes/makefuncs.c
index c6fb571982..3dcfe108fb 100644
--- a/src/backend/nodes/makefuncs.c
+++ b/src/backend/nodes/makefuncs.c
@@ -718,6 +718,17 @@ make_ands_explicit(List *andclauses)
 		return make_andclause(andclauses);
 }
 
+Expr *
+make_ors_explicit(List *orclauses)
+{
+	if (orclauses == NIL)
+		return (Expr *) makeBoolConst(true, false);
+	else if (list_length(orclauses) == 1)
+		return (Expr *) linitial(orclauses);
+	else
+		return make_orclause(orclauses);
+}
+
 List *
 make_ands_implicit(Expr *clause)
 {
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 34ca6d4ac2..0f26660cbb 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5380,12 +5380,27 @@ order_qual_clauses(PlannerInfo *root, List *clauses)
 static void
 copy_generic_path_info(Plan *dest, Path *src)
 {
+	ListCell *lc;
+
 	dest->startup_cost = src->startup_cost;
 	dest->total_cost = src->total_cost;
 	dest->plan_rows = src->rows;
 	dest->plan_width = src->pathtarget->width;
 	dest->parallel_aware = src->parallel_aware;
 	dest->parallel_safe = src->parallel_safe;
+
+	dest->applied_stats = src->parent->applied_stats;
+	dest->applied_clauses_or = src->parent->applied_clauses_or;
+
+	dest->applied_clauses = NIL;
+	foreach (lc, src->parent->applied_clauses)
+	{
+		List *clauses = (List *) lfirst(lc);
+
+		dest->applied_clauses
+			= lappend(dest->applied_clauses,
+					  maybe_extract_actual_clauses(clauses, false));
+	}
 }
 
 /*
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index 5d83f60eb9..fb177d9ac3 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -285,6 +285,10 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 	rel->partexprs = NULL;
 	rel->nullable_partexprs = NULL;
 
+	rel->applied_stats = NIL;
+	rel->applied_clauses = NIL;
+	rel->applied_clauses_or = NIL;
+
 	/*
 	 * Pass assorted information down the inheritance hierarchy.
 	 */
@@ -746,6 +750,10 @@ build_join_rel(PlannerInfo *root,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to the foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
@@ -939,6 +947,10 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index d6d26a2b51..80bf7143f5 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -508,6 +508,41 @@ extract_actual_clauses(List *restrictinfo_list,
 	return result;
 }
 
+/*
+ * maybe_extract_actual_clauses
+ *
+ * Just like extract_actual_clauses, but does not require the clauses to
+ * already be RestrictInfo.
+ *
+ * XXX Does not handle RestrictInfos nested in OR clauses.
+ */
+List *
+maybe_extract_actual_clauses(List *restrictinfo_list,
+							 bool pseudoconstant)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, restrictinfo_list)
+	{
+		RestrictInfo   *rinfo;
+		Node *node = (Node *) lfirst(l);
+
+		if (!IsA(node, RestrictInfo))
+		{
+			result = lappend(result, node);
+			continue;
+		}
+
+		rinfo = (RestrictInfo *) node;
+
+		if (rinfo->pseudoconstant == pseudoconstant)
+			result = lappend(result, rinfo->clause);
+	}
+
+	return result;
+}
+
 /*
  * extract_actual_join_clauses
  *
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index 7f014a0cbb..5d3f8f54df 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1858,6 +1858,11 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 			list_exprs[listidx] = NULL;
 		}
 
+		/* add it to the list of applied stats/clauses */
+		rel->applied_stats = lappend(rel->applied_stats, stat);
+		rel->applied_clauses = lappend(rel->applied_clauses, stat_clauses);
+		rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, (is_or) ? 1 : 0);
+
 		if (is_or)
 		{
 			bool	   *or_matches = NULL;
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index e11d022827..9e32abc7f9 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4039,6 +4039,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 		ListCell   *lc2;
 		Bitmapset  *matched = NULL;
 		AttrNumber	attnum_offset;
+		List	   *matched_exprs = NIL;
 
 		/*
 		 * How much we need to offset the attnums? If there are no
@@ -4086,6 +4087,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 				matched = bms_add_member(matched, attnum);
 
+				/* track expressions matched by this statistics */
+				matched_exprs = lappend(matched_exprs, varinfo->var);
+
 				found = true;
 			}
 
@@ -4114,6 +4118,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 					matched = bms_add_member(matched, attnum);
 
+					/* track expressions matched by this statistics */
+					matched_exprs = lappend(matched_exprs, expr);
+
 					/* there should be just one matching expression */
 					break;
 				}
@@ -4122,6 +4129,10 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 			}
 		}
 
+		rel->applied_stats = lappend(rel->applied_stats, matched_info);
+		rel->applied_clauses = lappend(rel->applied_clauses, matched_exprs);
+		rel->applied_clauses_or = lappend(rel->applied_clauses_or, 0);
+
 		/* Find the specific item that exactly matches the combination */
 		for (i = 0; i < stats->nitems; i++)
 		{
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index fc6d267e44..d3412f0c2a 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -33,6 +33,7 @@
 #include "catalog/pg_proc.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_subscription.h"
 #include "catalog/pg_transform.h"
 #include "catalog/pg_type.h"
@@ -3696,3 +3697,51 @@ get_subscription_name(Oid subid, bool missing_ok)
 
 	return subname;
 }
+
+/*
+ * get_statistics_name
+ *		Returns the name of a given extended statistics
+ *
+ * Returns a palloc'd copy of the string, or NULL if no such namespace.
+ */
+char *
+get_statistics_name(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		char	   *result;
+
+		result = pstrdup(NameStr(stxtup->stxname));
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return NULL;
+}
+
+/*
+ * get_statistics_namespace
+ *		Returns the namespace OID of a given extended statistics
+ */
+Oid
+get_statistics_namespace(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		Oid		result;
+
+		result = stxtup->stxnamespace;
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return InvalidOid;
+}
diff --git a/src/include/nodes/makefuncs.h b/src/include/nodes/makefuncs.h
index 3180703005..6af24e60b7 100644
--- a/src/include/nodes/makefuncs.h
+++ b/src/include/nodes/makefuncs.h
@@ -94,6 +94,8 @@ extern Node *make_and_qual(Node *qual1, Node *qual2);
 extern Expr *make_ands_explicit(List *andclauses);
 extern List *make_ands_implicit(Expr *clause);
 
+extern Expr *make_ors_explicit(List *orclauses);
+
 extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
 								List *expressions, List *predicates,
 								bool unique, bool nulls_not_distinct,
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index ed85dc7414..aee7e57541 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1028,6 +1028,11 @@ typedef struct RelOptInfo
 	List	  **partexprs pg_node_attr(read_write_ignore);
 	/* Nullable partition key expressions */
 	List	  **nullable_partexprs pg_node_attr(read_write_ignore);
+
+	/* info about applied extended statistics */
+	List       *applied_stats;		/* list of StatisticExtInfo */
+	List       *applied_clauses;	/* list of lists (of clauses) */
+	List       *applied_clauses_or;	/* are the clauses AND or OR */
 } RelOptInfo;
 
 /*
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index d40af8e59f..2ff7acf9d5 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -169,6 +169,11 @@ typedef struct Plan
 	 */
 	Bitmapset  *extParam;
 	Bitmapset  *allParam;
+
+	/* info about applied statistics */
+	List	   *applied_stats;
+	List	   *applied_clauses;
+	List	   *applied_clauses_or;
 } Plan;
 
 /* ----------------
diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index e140e619ac..ff1082c4fb 100644
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -39,6 +39,8 @@ extern bool restriction_is_securely_promotable(RestrictInfo *restrictinfo,
 extern List *get_actual_clauses(List *restrictinfo_list);
 extern List *extract_actual_clauses(List *restrictinfo_list,
 									bool pseudoconstant);
+extern List *maybe_extract_actual_clauses(List *restrictinfo_list,
+										  bool pseudoconstant);
 extern void extract_actual_join_clauses(List *restrictinfo_list,
 										Relids joinrelids,
 										List **joinquals,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index c22cabdf42..0a85cc38b3 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -204,6 +204,9 @@ extern char *get_publication_name(Oid pubid, bool missing_ok);
 extern Oid	get_subscription_oid(const char *subname, bool missing_ok);
 extern char *get_subscription_name(Oid subid, bool missing_ok);
 
+extern char *get_statistics_name(Oid stxid);
+extern Oid	get_statistics_namespace(Oid stxid);
+
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
 #define type_is_array_domain(typid)  (get_base_element_type(typid) != InvalidOid)

From 5e78a80ad51b1e9436c43d3422056cdc8d1117d3 Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Wed, 26 Jun 2024 17:03:34 +0900
Subject: [PATCH] Add Showing applied extended statistics in explain r3.

This patch fixes the following points of issues as Tomas mentioned
before:

1. Previously, clauses in Grouping queries were incorrectly displayed as
   And lists, but have now been fixed to display them as comma lists.

2. To reduce overhead, extended statistics information is now tracked
   only when the verbose option is selected.

Also, The strings displayed in Explain were replaced with the following:

s/Statistics/Ext Stats/
---
 src/backend/commands/explain.c            | 114 ++++++++++++++++++++++
 src/backend/nodes/makefuncs.c             |  11 +++
 src/backend/optimizer/plan/createplan.c   |  15 +++
 src/backend/optimizer/util/relnode.c      |  12 +++
 src/backend/optimizer/util/restrictinfo.c |  35 +++++++
 src/backend/statistics/extended_stats.c   |   8 ++
 src/backend/utils/adt/selfuncs.c          |  15 +++
 src/backend/utils/cache/lsyscache.c       |  49 ++++++++++
 src/include/nodes/makefuncs.h             |   2 +
 src/include/nodes/parsenodes.h            |   3 +
 src/include/nodes/pathnodes.h             |   5 +
 src/include/nodes/plannodes.h             |   5 +
 src/include/optimizer/restrictinfo.h      |   2 +
 src/include/utils/lsyscache.h             |   3 +
 14 files changed, 279 insertions(+)

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 94511a5a02..7e39d37b59 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -94,6 +94,9 @@ static void show_qual(List *qual, const char *qlabel,
 static void show_scan_qual(List *qual, const char *qlabel,
 						   PlanState *planstate, List *ancestors,
 						   ExplainState *es);
+static void show_scan_stats(List *stats, List *clauses, List *ors,
+							PlanState *planstate, List *ancestors,
+							ExplainState *es);
 static void show_upper_qual(List *qual, const char *qlabel,
 							PlanState *planstate, List *ancestors,
 							ExplainState *es);
@@ -483,6 +486,11 @@ standard_ExplainOneQuery(Query *query, int cursorOptions,
 
 	if (es->buffers)
 		bufusage_start = pgBufferUsage;
+
+	/* if this flag is true, applied ext stats are stored */
+	if (es->verbose)
+		query->isExplain = true;
+
 	INSTR_TIME_SET_CURRENT(planstart);
 
 	/* plan the query */
@@ -1975,6 +1983,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_IndexOnlyScan:
 			show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
@@ -1991,10 +2003,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (es->analyze)
 				ExplainPropertyFloat("Heap Fetches", NULL,
 									 planstate->instrument->ntuples2, 0, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapHeapScan:
 			show_scan_qual(((BitmapHeapScan *) plan)->bitmapqualorig,
@@ -2024,6 +2044,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Gather:
 			{
@@ -2203,6 +2227,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_WindowAgg:
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
@@ -2218,6 +2246,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->verbose)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Sort:
 			show_sort_keys(castNode(SortState, planstate), ancestors, es);
@@ -2537,6 +2569,88 @@ show_scan_qual(List *qual, const char *qlabel,
 	show_qual(qual, qlabel, planstate, ancestors, useprefix, es);
 }
 
+/*
+ * Show a generic expression
+ */
+static char *
+deparse_stat_expression(Node *node,
+						PlanState *planstate, List *ancestors,
+						ExplainState *es)
+{
+	List	   *context;
+
+	/* Set up deparsing context */
+	context = set_deparse_context_plan(es->deparse_cxt,
+									   planstate->plan,
+									   ancestors);
+
+	/* Deparse the expression */
+	return deparse_expression(node, context, false, false);
+}
+
+/*
+ * Show a qualifier expression (which is a List with implicit AND semantics)
+ */
+static char *
+show_stat_qual(List *qual, int is_or,
+			   PlanState *planstate, List *ancestors,
+			   ExplainState *es)
+{
+	Node	   *node;
+
+	/* No work if empty qual */
+	if (qual == NIL)
+		return NULL;
+
+	/* Convert AND list to explicit AND */
+	switch (is_or)
+	{
+		case 0:
+			node = (Node *) make_ands_explicit(qual);
+			break;
+		case 1:
+			node = (Node *) make_ors_explicit(qual);
+			break;
+		case 2:
+			/* Extended stats for GROUP BY clause should be comma separeted string */
+			node = (Node *) qual;
+			break;
+		default:
+			elog(ERROR, "unexpected value: %d", is_or);
+			break;
+	}
+
+	/* And show it */
+	return deparse_stat_expression(node, planstate, ancestors, es);
+}
+
+/*
+ * Show applied statistics for scan/agg/group plan node
+ */
+static void
+show_scan_stats(List *stats, List *clauses, List *ors,
+				PlanState *planstate, List *ancestors, ExplainState *es)
+{
+	ListCell   *lc1, *lc2, *lc3;
+	StringInfoData	str;
+
+	forthree (lc1, stats, lc2, clauses, lc3, ors)
+	{
+		StatisticExtInfo   *stat = (StatisticExtInfo *) lfirst(lc1);
+		List   *applied_clauses = (List *) lfirst(lc2);
+		int		is_or = lfirst_int(lc3);
+
+		initStringInfo(&str);
+
+		appendStringInfo(&str, "%s.%s  Clauses: %s",
+						 get_namespace_name(get_statistics_namespace(stat->statOid)),
+						 get_statistics_name(stat->statOid),
+						 show_stat_qual(applied_clauses, is_or, planstate, ancestors, es));
+
+		ExplainPropertyText("Ext Stats", str.data, es);
+	}
+}
+
 /*
  * Show a qualifier expression for an upper-level plan node
  */
diff --git a/src/backend/nodes/makefuncs.c b/src/backend/nodes/makefuncs.c
index 61ac172a85..725c76ab63 100644
--- a/src/backend/nodes/makefuncs.c
+++ b/src/backend/nodes/makefuncs.c
@@ -733,6 +733,17 @@ make_ands_explicit(List *andclauses)
 		return make_andclause(andclauses);
 }
 
+Expr *
+make_ors_explicit(List *orclauses)
+{
+	if (orclauses == NIL)
+		return (Expr *) makeBoolConst(true, false);
+	else if (list_length(orclauses) == 1)
+		return (Expr *) linitial(orclauses);
+	else
+		return make_orclause(orclauses);
+}
+
 List *
 make_ands_implicit(Expr *clause)
 {
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 6b64c4a362..25541308f4 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5408,12 +5408,27 @@ order_qual_clauses(PlannerInfo *root, List *clauses)
 static void
 copy_generic_path_info(Plan *dest, Path *src)
 {
+	ListCell *lc;
+
 	dest->startup_cost = src->startup_cost;
 	dest->total_cost = src->total_cost;
 	dest->plan_rows = src->rows;
 	dest->plan_width = src->pathtarget->width;
 	dest->parallel_aware = src->parallel_aware;
 	dest->parallel_safe = src->parallel_safe;
+
+	dest->applied_stats = src->parent->applied_stats;
+	dest->applied_clauses_or = src->parent->applied_clauses_or;
+
+	dest->applied_clauses = NIL;
+	foreach (lc, src->parent->applied_clauses)
+	{
+		List *clauses = (List *) lfirst(lc);
+
+		dest->applied_clauses
+			= lappend(dest->applied_clauses,
+					  maybe_extract_actual_clauses(clauses, false));
+	}
 }
 
 /*
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index e05b21c884..637f730a8e 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -287,6 +287,10 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 	rel->partexprs = NULL;
 	rel->nullable_partexprs = NULL;
 
+	rel->applied_stats = NIL;
+	rel->applied_clauses = NIL;
+	rel->applied_clauses_or = NIL;
+
 	/*
 	 * Pass assorted information down the inheritance hierarchy.
 	 */
@@ -769,6 +773,10 @@ build_join_rel(PlannerInfo *root,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to the foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
@@ -963,6 +971,10 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index 0b406e9334..23136a330b 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -508,6 +508,41 @@ extract_actual_clauses(List *restrictinfo_list,
 	return result;
 }
 
+/*
+ * maybe_extract_actual_clauses
+ *
+ * Just like extract_actual_clauses, but does not require the clauses to
+ * already be RestrictInfo.
+ *
+ * XXX Does not handle RestrictInfos nested in OR clauses.
+ */
+List *
+maybe_extract_actual_clauses(List *restrictinfo_list,
+							 bool pseudoconstant)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, restrictinfo_list)
+	{
+		RestrictInfo   *rinfo;
+		Node *node = (Node *) lfirst(l);
+
+		if (!IsA(node, RestrictInfo))
+		{
+			result = lappend(result, node);
+			continue;
+		}
+
+		rinfo = (RestrictInfo *) node;
+
+		if (rinfo->pseudoconstant == pseudoconstant)
+			result = lappend(result, rinfo->clause);
+	}
+
+	return result;
+}
+
 /*
  * extract_actual_join_clauses
  *
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index 99fdf208db..4d92f24c61 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1857,6 +1857,14 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 			list_exprs[listidx] = NULL;
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, stat);
+			rel->applied_clauses = lappend(rel->applied_clauses, stat_clauses);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, (is_or) ? 1 : 0);
+		}
+
 		if (is_or)
 		{
 			bool	   *or_matches = NULL;
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 5f5d7959d8..2aec61e7bb 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4069,6 +4069,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 		ListCell   *lc2;
 		Bitmapset  *matched = NULL;
 		AttrNumber	attnum_offset;
+		List	   *matched_exprs = NIL;
 
 		/*
 		 * How much we need to offset the attnums? If there are no
@@ -4116,6 +4117,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 				matched = bms_add_member(matched, attnum);
 
+				/* track expressions matched by this statistics */
+				matched_exprs = lappend(matched_exprs, varinfo->var);
+
 				found = true;
 			}
 
@@ -4144,6 +4148,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 					matched = bms_add_member(matched, attnum);
 
+					/* track expressions matched by this statistics */
+					matched_exprs = lappend(matched_exprs, expr);
+
 					/* there should be just one matching expression */
 					break;
 				}
@@ -4152,6 +4159,14 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 			}
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, matched_info);
+			rel->applied_clauses = lappend(rel->applied_clauses, matched_exprs);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, 2); /* 2: Use comma to deparse */
+		}
+
 		/* Find the specific item that exactly matches the combination */
 		for (i = 0; i < stats->nitems; i++)
 		{
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 48a280d089..d135751dd0 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -35,6 +35,7 @@
 #include "catalog/pg_publication.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_subscription.h"
 #include "catalog/pg_transform.h"
 #include "catalog/pg_type.h"
@@ -3714,3 +3715,51 @@ get_subscription_name(Oid subid, bool missing_ok)
 
 	return subname;
 }
+
+/*
+ * get_statistics_name
+ *		Returns the name of a given extended statistics
+ *
+ * Returns a palloc'd copy of the string, or NULL if no such namespace.
+ */
+char *
+get_statistics_name(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		char	   *result;
+
+		result = pstrdup(NameStr(stxtup->stxname));
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return NULL;
+}
+
+/*
+ * get_statistics_namespace
+ *		Returns the namespace OID of a given extended statistics
+ */
+Oid
+get_statistics_namespace(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		Oid		result;
+
+		result = stxtup->stxnamespace;
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return InvalidOid;
+}
diff --git a/src/include/nodes/makefuncs.h b/src/include/nodes/makefuncs.h
index 5209d3de89..f5ae402c16 100644
--- a/src/include/nodes/makefuncs.h
+++ b/src/include/nodes/makefuncs.h
@@ -94,6 +94,8 @@ extern Node *make_and_qual(Node *qual1, Node *qual2);
 extern Expr *make_ands_explicit(List *andclauses);
 extern List *make_ands_implicit(Expr *clause);
 
+extern Expr *make_ors_explicit(List *orclauses);
+
 extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
 								List *expressions, List *predicates,
 								bool unique, bool nulls_not_distinct,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 85a62b538e..36b479c104 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -238,6 +238,9 @@ typedef struct Query
 	ParseLoc	stmt_location;
 	/* length in bytes; 0 means "rest of string" */
 	ParseLoc	stmt_len pg_node_attr(query_jumble_ignore);
+
+	/* if true, query is explain verbose */
+	bool        isExplain;
 } Query;
 
 
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 2ba297c117..d78f08c3c4 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1043,6 +1043,11 @@ typedef struct RelOptInfo
 	List	  **partexprs pg_node_attr(read_write_ignore);
 	/* Nullable partition key expressions */
 	List	  **nullable_partexprs pg_node_attr(read_write_ignore);
+
+	/* info about applied extended statistics */
+	List       *applied_stats;		/* list of StatisticExtInfo */
+	List       *applied_clauses;	/* list of lists of clauses */
+	List       *applied_clauses_or;	/* are the clauses AND, OR, or Comma */
 } RelOptInfo;
 
 /*
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 1aeeaec95e..504e5cc475 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -169,6 +169,11 @@ typedef struct Plan
 	 */
 	Bitmapset  *extParam;
 	Bitmapset  *allParam;
+
+	/* info about applied statistics */
+	List	   *applied_stats;
+	List	   *applied_clauses;
+	List	   *applied_clauses_or;
 } Plan;
 
 /* ----------------
diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index 1b42c832c5..29aa519b99 100644
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -39,6 +39,8 @@ extern bool restriction_is_securely_promotable(RestrictInfo *restrictinfo,
 extern List *get_actual_clauses(List *restrictinfo_list);
 extern List *extract_actual_clauses(List *restrictinfo_list,
 									bool pseudoconstant);
+extern List *maybe_extract_actual_clauses(List *restrictinfo_list,
+										  bool pseudoconstant);
 extern void extract_actual_join_clauses(List *restrictinfo_list,
 										Relids joinrelids,
 										List **joinquals,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 20446f6f83..3fab6d5eea 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -206,6 +206,9 @@ extern char *get_publication_name(Oid pubid, bool missing_ok);
 extern Oid	get_subscription_oid(const char *subname, bool missing_ok);
 extern char *get_subscription_name(Oid subid, bool missing_ok);
 
+extern char *get_statistics_name(Oid stxid);
+extern Oid	get_statistics_namespace(Oid stxid);
+
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
 #define type_is_array_domain(typid)  (get_base_element_type(typid) != InvalidOid)
-- 
2.39.3

From f739a85886cddb160885f22fa5c2bd56c1a23c5c Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Wed, 26 Jun 2024 17:03:34 +0900
Subject: [PATCH] Add a new option STATS to Explain command

It shows applied extended statistics in Explain command output.
This patch fixes the following points:

- Fix deparsed clauses of Grouping query
    Previously, it was incorrectly displayed as Anded-lists. However,
    it was fixed to comma lists.

- To reduce overhead, extended statistics information is now tracked
    only when the STATS option is selected.

- s/Statistics/Ext Stats/
    "Statistics" seemed ambiguous, so I changed it to "Ext Stats".
    I'm not sure whether Ext Stats is preferable or not.

- Fix document for the STATS option partly, and todo list is below:
    Todo
    - sql-createstatistics.html
        Add Explain outputs using STATS option

    - planner-stats.html
        Should I introduce Explain with the STATS option on this page?
---
 doc/src/sgml/ref/explain.sgml             |  13 +++
 src/backend/commands/explain.c            | 116 ++++++++++++++++++++++
 src/backend/nodes/makefuncs.c             |  11 ++
 src/backend/optimizer/plan/createplan.c   |  15 +++
 src/backend/optimizer/util/relnode.c      |  12 +++
 src/backend/optimizer/util/restrictinfo.c |  35 +++++++
 src/backend/statistics/extended_stats.c   |   8 ++
 src/backend/utils/adt/selfuncs.c          |  15 +++
 src/backend/utils/cache/lsyscache.c       |  49 +++++++++
 src/include/commands/explain.h            |   1 +
 src/include/nodes/makefuncs.h             |   2 +
 src/include/nodes/parsenodes.h            |   3 +
 src/include/nodes/pathnodes.h             |   5 +
 src/include/nodes/plannodes.h             |   5 +
 src/include/optimizer/restrictinfo.h      |   2 +
 src/include/utils/lsyscache.h             |   3 +
 16 files changed, 295 insertions(+)

diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index db9d3a8549..b573152b6e 100644
--- a/doc/src/sgml/ref/explain.sgml
+++ b/doc/src/sgml/ref/explain.sgml
@@ -43,6 +43,7 @@ EXPLAIN [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] <rep
     BUFFERS [ <replaceable class="parameter">boolean</replaceable> ]
     SERIALIZE [ { NONE | TEXT | BINARY } ]
     WAL [ <replaceable class="parameter">boolean</replaceable> ]
+    STATS [ <replaceable class="parameter">boolean</replaceable> ]
     TIMING [ <replaceable class="parameter">boolean</replaceable> ]
     SUMMARY [ <replaceable class="parameter">boolean</replaceable> ]
     MEMORY [ <replaceable class="parameter">boolean</replaceable> ]
@@ -248,6 +249,18 @@ ROLLBACK;
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>STATS</literal></term>
+    <listitem>
+     <para>
+      Include information on applied <literal>Extended statistics</literal>.
+      Specifically, include the names of extended statistics and clauses.
+      See <xref linkend="planner-stats-extended"/> for details about extended
+      statistics. This parameter defaults to <literal>FALSE</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>TIMING</literal></term>
     <listitem>
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 94511a5a02..0fd93b52e5 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -94,6 +94,9 @@ static void show_qual(List *qual, const char *qlabel,
 static void show_scan_qual(List *qual, const char *qlabel,
 						   PlanState *planstate, List *ancestors,
 						   ExplainState *es);
+static void show_scan_stats(List *stats, List *clauses, List *ors,
+							PlanState *planstate, List *ancestors,
+							ExplainState *es);
 static void show_upper_qual(List *qual, const char *qlabel,
 							PlanState *planstate, List *ancestors,
 							ExplainState *es);
@@ -210,6 +213,8 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt,
 			es->settings = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "generic_plan") == 0)
 			es->generic = defGetBoolean(opt);
+		else if (strcmp(opt->defname, "stats") == 0)
+			es->stats = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "timing") == 0)
 		{
 			timing_set = true;
@@ -483,6 +488,11 @@ standard_ExplainOneQuery(Query *query, int cursorOptions,
 
 	if (es->buffers)
 		bufusage_start = pgBufferUsage;
+
+	/* if this flag is true, applied ext stats are stored */
+	if (es->stats)
+		query->isExplain_Stats = true;
+
 	INSTR_TIME_SET_CURRENT(planstart);
 
 	/* plan the query */
@@ -1975,6 +1985,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_IndexOnlyScan:
 			show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
@@ -1991,10 +2005,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (es->analyze)
 				ExplainPropertyFloat("Heap Fetches", NULL,
 									 planstate->instrument->ntuples2, 0, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapHeapScan:
 			show_scan_qual(((BitmapHeapScan *) plan)->bitmapqualorig,
@@ -2024,6 +2046,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Gather:
 			{
@@ -2203,6 +2229,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_WindowAgg:
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
@@ -2218,6 +2248,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Sort:
 			show_sort_keys(castNode(SortState, planstate), ancestors, es);
@@ -2537,6 +2571,88 @@ show_scan_qual(List *qual, const char *qlabel,
 	show_qual(qual, qlabel, planstate, ancestors, useprefix, es);
 }
 
+/*
+ * Show a generic expression
+ */
+static char *
+deparse_stat_expression(Node *node,
+						PlanState *planstate, List *ancestors,
+						ExplainState *es)
+{
+	List	   *context;
+
+	/* Set up deparsing context */
+	context = set_deparse_context_plan(es->deparse_cxt,
+									   planstate->plan,
+									   ancestors);
+
+	/* Deparse the expression */
+	return deparse_expression(node, context, false, false);
+}
+
+/*
+ * Show a qualifier expression (which is a List with implicit AND semantics)
+ */
+static char *
+show_stat_qual(List *qual, int is_or,
+			   PlanState *planstate, List *ancestors,
+			   ExplainState *es)
+{
+	Node	   *node;
+
+	/* No work if empty qual */
+	if (qual == NIL)
+		return NULL;
+
+	/* Convert AND list to explicit AND */
+	switch (is_or)
+	{
+		case 0:
+			node = (Node *) make_ands_explicit(qual);
+			break;
+		case 1:
+			node = (Node *) make_ors_explicit(qual);
+			break;
+		case 2:
+			/* Extended stats for GROUP BY clause should be comma separeted string */
+			node = (Node *) qual;
+			break;
+		default:
+			elog(ERROR, "unexpected value: %d", is_or);
+			break;
+	}
+
+	/* And show it */
+	return deparse_stat_expression(node, planstate, ancestors, es);
+}
+
+/*
+ * Show applied statistics for scan/agg/group plan node
+ */
+static void
+show_scan_stats(List *stats, List *clauses, List *ors,
+				PlanState *planstate, List *ancestors, ExplainState *es)
+{
+	ListCell   *lc1, *lc2, *lc3;
+	StringInfoData	str;
+
+	forthree (lc1, stats, lc2, clauses, lc3, ors)
+	{
+		StatisticExtInfo   *stat = (StatisticExtInfo *) lfirst(lc1);
+		List   *applied_clauses = (List *) lfirst(lc2);
+		int		is_or = lfirst_int(lc3);
+
+		initStringInfo(&str);
+
+		appendStringInfo(&str, "%s.%s  Clauses: %s",
+						 get_namespace_name(get_statistics_namespace(stat->statOid)),
+						 get_statistics_name(stat->statOid),
+						 show_stat_qual(applied_clauses, is_or, planstate, ancestors, es));
+
+		ExplainPropertyText("Ext Stats", str.data, es);
+	}
+}
+
 /*
  * Show a qualifier expression for an upper-level plan node
  */
diff --git a/src/backend/nodes/makefuncs.c b/src/backend/nodes/makefuncs.c
index 61ac172a85..725c76ab63 100644
--- a/src/backend/nodes/makefuncs.c
+++ b/src/backend/nodes/makefuncs.c
@@ -733,6 +733,17 @@ make_ands_explicit(List *andclauses)
 		return make_andclause(andclauses);
 }
 
+Expr *
+make_ors_explicit(List *orclauses)
+{
+	if (orclauses == NIL)
+		return (Expr *) makeBoolConst(true, false);
+	else if (list_length(orclauses) == 1)
+		return (Expr *) linitial(orclauses);
+	else
+		return make_orclause(orclauses);
+}
+
 List *
 make_ands_implicit(Expr *clause)
 {
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 6b64c4a362..25541308f4 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5408,12 +5408,27 @@ order_qual_clauses(PlannerInfo *root, List *clauses)
 static void
 copy_generic_path_info(Plan *dest, Path *src)
 {
+	ListCell *lc;
+
 	dest->startup_cost = src->startup_cost;
 	dest->total_cost = src->total_cost;
 	dest->plan_rows = src->rows;
 	dest->plan_width = src->pathtarget->width;
 	dest->parallel_aware = src->parallel_aware;
 	dest->parallel_safe = src->parallel_safe;
+
+	dest->applied_stats = src->parent->applied_stats;
+	dest->applied_clauses_or = src->parent->applied_clauses_or;
+
+	dest->applied_clauses = NIL;
+	foreach (lc, src->parent->applied_clauses)
+	{
+		List *clauses = (List *) lfirst(lc);
+
+		dest->applied_clauses
+			= lappend(dest->applied_clauses,
+					  maybe_extract_actual_clauses(clauses, false));
+	}
 }
 
 /*
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index e05b21c884..637f730a8e 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -287,6 +287,10 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 	rel->partexprs = NULL;
 	rel->nullable_partexprs = NULL;
 
+	rel->applied_stats = NIL;
+	rel->applied_clauses = NIL;
+	rel->applied_clauses_or = NIL;
+
 	/*
 	 * Pass assorted information down the inheritance hierarchy.
 	 */
@@ -769,6 +773,10 @@ build_join_rel(PlannerInfo *root,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to the foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
@@ -963,6 +971,10 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index 0b406e9334..23136a330b 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -508,6 +508,41 @@ extract_actual_clauses(List *restrictinfo_list,
 	return result;
 }
 
+/*
+ * maybe_extract_actual_clauses
+ *
+ * Just like extract_actual_clauses, but does not require the clauses to
+ * already be RestrictInfo.
+ *
+ * XXX Does not handle RestrictInfos nested in OR clauses.
+ */
+List *
+maybe_extract_actual_clauses(List *restrictinfo_list,
+							 bool pseudoconstant)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, restrictinfo_list)
+	{
+		RestrictInfo   *rinfo;
+		Node *node = (Node *) lfirst(l);
+
+		if (!IsA(node, RestrictInfo))
+		{
+			result = lappend(result, node);
+			continue;
+		}
+
+		rinfo = (RestrictInfo *) node;
+
+		if (rinfo->pseudoconstant == pseudoconstant)
+			result = lappend(result, rinfo->clause);
+	}
+
+	return result;
+}
+
 /*
  * extract_actual_join_clauses
  *
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index 99fdf208db..dbf921118e 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1857,6 +1857,14 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 			list_exprs[listidx] = NULL;
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, stat);
+			rel->applied_clauses = lappend(rel->applied_clauses, stat_clauses);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, (is_or) ? 1 : 0);
+		}
+
 		if (is_or)
 		{
 			bool	   *or_matches = NULL;
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 5f5d7959d8..21feb92a58 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4069,6 +4069,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 		ListCell   *lc2;
 		Bitmapset  *matched = NULL;
 		AttrNumber	attnum_offset;
+		List	   *matched_exprs = NIL;
 
 		/*
 		 * How much we need to offset the attnums? If there are no
@@ -4116,6 +4117,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 				matched = bms_add_member(matched, attnum);
 
+				/* track expressions matched by this statistics */
+				matched_exprs = lappend(matched_exprs, varinfo->var);
+
 				found = true;
 			}
 
@@ -4144,6 +4148,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 					matched = bms_add_member(matched, attnum);
 
+					/* track expressions matched by this statistics */
+					matched_exprs = lappend(matched_exprs, expr);
+
 					/* there should be just one matching expression */
 					break;
 				}
@@ -4152,6 +4159,14 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 			}
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, matched_info);
+			rel->applied_clauses = lappend(rel->applied_clauses, matched_exprs);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, 2); /* 2: Use comma to deparse */
+		}
+
 		/* Find the specific item that exactly matches the combination */
 		for (i = 0; i < stats->nitems; i++)
 		{
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index 48a280d089..d135751dd0 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -35,6 +35,7 @@
 #include "catalog/pg_publication.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_subscription.h"
 #include "catalog/pg_transform.h"
 #include "catalog/pg_type.h"
@@ -3714,3 +3715,51 @@ get_subscription_name(Oid subid, bool missing_ok)
 
 	return subname;
 }
+
+/*
+ * get_statistics_name
+ *		Returns the name of a given extended statistics
+ *
+ * Returns a palloc'd copy of the string, or NULL if no such namespace.
+ */
+char *
+get_statistics_name(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		char	   *result;
+
+		result = pstrdup(NameStr(stxtup->stxname));
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return NULL;
+}
+
+/*
+ * get_statistics_namespace
+ *		Returns the namespace OID of a given extended statistics
+ */
+Oid
+get_statistics_namespace(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		Oid		result;
+
+		result = stxtup->stxnamespace;
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return InvalidOid;
+}
diff --git a/src/include/commands/explain.h b/src/include/commands/explain.h
index 9b8b351d9a..f9da3c6f7c 100644
--- a/src/include/commands/explain.h
+++ b/src/include/commands/explain.h
@@ -55,6 +55,7 @@ typedef struct ExplainState
 	bool		memory;			/* print planner's memory usage information */
 	bool		settings;		/* print modified settings */
 	bool		generic;		/* generate a generic plan */
+	bool		stats;			/* generate a generic plan */
 	ExplainSerializeOption serialize;	/* serialize the query's output? */
 	ExplainFormat format;		/* output format */
 	/* state for output formatting --- not reset for each new plan tree */
diff --git a/src/include/nodes/makefuncs.h b/src/include/nodes/makefuncs.h
index 5209d3de89..f5ae402c16 100644
--- a/src/include/nodes/makefuncs.h
+++ b/src/include/nodes/makefuncs.h
@@ -94,6 +94,8 @@ extern Node *make_and_qual(Node *qual1, Node *qual2);
 extern Expr *make_ands_explicit(List *andclauses);
 extern List *make_ands_implicit(Expr *clause);
 
+extern Expr *make_ors_explicit(List *orclauses);
+
 extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
 								List *expressions, List *predicates,
 								bool unique, bool nulls_not_distinct,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 85a62b538e..d148aabad4 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -238,6 +238,9 @@ typedef struct Query
 	ParseLoc	stmt_location;
 	/* length in bytes; 0 means "rest of string" */
 	ParseLoc	stmt_len pg_node_attr(query_jumble_ignore);
+
+	/* if true, query is explain with stats option */
+	bool        isExplain_Stats;
 } Query;
 
 
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 2ba297c117..d78f08c3c4 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1043,6 +1043,11 @@ typedef struct RelOptInfo
 	List	  **partexprs pg_node_attr(read_write_ignore);
 	/* Nullable partition key expressions */
 	List	  **nullable_partexprs pg_node_attr(read_write_ignore);
+
+	/* info about applied extended statistics */
+	List       *applied_stats;		/* list of StatisticExtInfo */
+	List       *applied_clauses;	/* list of lists of clauses */
+	List       *applied_clauses_or;	/* are the clauses AND, OR, or Comma */
 } RelOptInfo;
 
 /*
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 1aeeaec95e..504e5cc475 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -169,6 +169,11 @@ typedef struct Plan
 	 */
 	Bitmapset  *extParam;
 	Bitmapset  *allParam;
+
+	/* info about applied statistics */
+	List	   *applied_stats;
+	List	   *applied_clauses;
+	List	   *applied_clauses_or;
 } Plan;
 
 /* ----------------
diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index 1b42c832c5..29aa519b99 100644
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -39,6 +39,8 @@ extern bool restriction_is_securely_promotable(RestrictInfo *restrictinfo,
 extern List *get_actual_clauses(List *restrictinfo_list);
 extern List *extract_actual_clauses(List *restrictinfo_list,
 									bool pseudoconstant);
+extern List *maybe_extract_actual_clauses(List *restrictinfo_list,
+										  bool pseudoconstant);
 extern void extract_actual_join_clauses(List *restrictinfo_list,
 										Relids joinrelids,
 										List **joinquals,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 20446f6f83..3fab6d5eea 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -206,6 +206,9 @@ extern char *get_publication_name(Oid pubid, bool missing_ok);
 extern Oid	get_subscription_oid(const char *subname, bool missing_ok);
 extern char *get_subscription_name(Oid subid, bool missing_ok);
 
+extern char *get_statistics_name(Oid stxid);
+extern Oid	get_statistics_namespace(Oid stxid);
+
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
 #define type_is_array_domain(typid)  (get_base_element_type(typid) != InvalidOid)
-- 
2.39.3

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 8c80c34619..7d3dcca655 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -2644,15 +2644,15 @@ show_scan_stats(List *stats, List *clauses, List *ors,
 
 	forthree (lc1, stats, lc2, clauses, lc3, ors)
 	{
-		StatisticExtInfo   *stat = (StatisticExtInfo *) lfirst(lc1);
+		Oid   statOid = lfirst_oid(lc1);
 		List   *applied_clauses = (List *) lfirst(lc2);
 		int		is_or = lfirst_int(lc3);
 
 		initStringInfo(&str);
 
 		appendStringInfo(&str, "%s.%s  Clauses: %s",
-						 get_namespace_name(get_statistics_namespace(stat->statOid)),
-						 get_statistics_name(stat->statOid),
+						 get_namespace_name(get_statistics_namespace(statOid)),
+						 get_statistics_name(statOid),
 						 show_stat_qual(applied_clauses, is_or, planstate, ancestors, es));
 
 		ExplainPropertyText("Ext Stats", str.data, es);
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index dbf921118e..79ab608160 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1860,7 +1860,7 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 		/* add it to the list of applied stats/clauses, if this flag is true */
 		if (root->parse->isExplain_Stats)
 		{
-			rel->applied_stats = lappend(rel->applied_stats, stat);
+			rel->applied_stats = lappend_oid(rel->applied_stats, stat->statOid);
 			rel->applied_clauses = lappend(rel->applied_clauses, stat_clauses);
 			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, (is_or) ? 1 : 0);
 		}
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 21feb92a58..42f5306ec7 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4162,7 +4162,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 		/* add it to the list of applied stats/clauses, if this flag is true */
 		if (root->parse->isExplain_Stats)
 		{
-			rel->applied_stats = lappend(rel->applied_stats, matched_info);
+			rel->applied_stats = lappend_oid(rel->applied_stats, matched_info->statOid);
 			rel->applied_clauses = lappend(rel->applied_clauses, matched_exprs);
 			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, 2); /* 2: Use comma to deparse */
 		}

From dc160dafc2f1a91d7b306f2d1e582a16c63f8c58 Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Fri, 1 Nov 2024 13:46:35 +0900
Subject: [PATCH] Add a new option STATS to Explain command

It shows applied extended statistics in Explain command output.
This patch fixes the following points:

- Rebased on 49d6c7d8

- Will fix document such as:
    Todo
    - sql-createstatistics.html
        Add Explain outputs using STATS option

    - planner-stats.html
        Should I introduce Explain with the STATS option on this page?
---
 doc/src/sgml/ref/explain.sgml             |  13 +++
 src/backend/commands/explain.c            | 121 ++++++++++++++++++++++
 src/backend/nodes/makefuncs.c             |  11 ++
 src/backend/optimizer/plan/createplan.c   |  15 +++
 src/backend/optimizer/util/relnode.c      |  12 +++
 src/backend/optimizer/util/restrictinfo.c |  35 +++++++
 src/backend/statistics/extended_stats.c   |   8 ++
 src/backend/utils/adt/selfuncs.c          |  15 +++
 src/backend/utils/cache/lsyscache.c       |  49 +++++++++
 src/include/commands/explain.h            |   1 +
 src/include/nodes/makefuncs.h             |   2 +
 src/include/nodes/parsenodes.h            |   3 +
 src/include/nodes/pathnodes.h             |   5 +
 src/include/nodes/plannodes.h             |   5 +
 src/include/optimizer/restrictinfo.h      |   2 +
 src/include/utils/lsyscache.h             |   3 +
 16 files changed, 300 insertions(+)

diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index db9d3a8549..b573152b6e 100644
--- a/doc/src/sgml/ref/explain.sgml
+++ b/doc/src/sgml/ref/explain.sgml
@@ -43,6 +43,7 @@ EXPLAIN [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] <rep
     BUFFERS [ <replaceable class="parameter">boolean</replaceable> ]
     SERIALIZE [ { NONE | TEXT | BINARY } ]
     WAL [ <replaceable class="parameter">boolean</replaceable> ]
+    STATS [ <replaceable class="parameter">boolean</replaceable> ]
     TIMING [ <replaceable class="parameter">boolean</replaceable> ]
     SUMMARY [ <replaceable class="parameter">boolean</replaceable> ]
     MEMORY [ <replaceable class="parameter">boolean</replaceable> ]
@@ -248,6 +249,18 @@ ROLLBACK;
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>STATS</literal></term>
+    <listitem>
+     <para>
+      Include information on applied <literal>Extended statistics</literal>.
+      Specifically, include the names of extended statistics and clauses.
+      See <xref linkend="planner-stats-extended"/> for details about extended
+      statistics. This parameter defaults to <literal>FALSE</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>TIMING</literal></term>
     <listitem>
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 7c0fd63b2f..40c8462d68 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -94,6 +94,9 @@ static void show_qual(List *qual, const char *qlabel,
 static void show_scan_qual(List *qual, const char *qlabel,
 						   PlanState *planstate, List *ancestors,
 						   ExplainState *es);
+static void show_scan_stats(List *stats, List *clauses, List *ors,
+							PlanState *planstate, List *ancestors,
+							ExplainState *es);
 static void show_upper_qual(List *qual, const char *qlabel,
 							PlanState *planstate, List *ancestors,
 							ExplainState *es);
@@ -219,6 +222,8 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt,
 			es->settings = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "generic_plan") == 0)
 			es->generic = defGetBoolean(opt);
+		else if (strcmp(opt->defname, "stats") == 0)
+			es->stats = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "timing") == 0)
 		{
 			timing_set = true;
@@ -490,6 +495,11 @@ standard_ExplainOneQuery(Query *query, int cursorOptions,
 
 	if (es->buffers)
 		bufusage_start = pgBufferUsage;
+
+	/* if this flag is true, applied ext stats are stored */
+	if (es->stats)
+		query->isExplain_Stats = true;
+
 	INSTR_TIME_SET_CURRENT(planstart);
 
 	/* plan the query */
@@ -2107,6 +2117,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_IndexOnlyScan:
 			show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
@@ -2123,10 +2137,18 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (es->analyze)
 				ExplainPropertyFloat("Heap Fetches", NULL,
 									 planstate->instrument->ntuples2, 0, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapHeapScan:
 			show_scan_qual(((BitmapHeapScan *) plan)->bitmapqualorig,
@@ -2157,6 +2179,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 										   planstate, es);
 			if (IsA(plan, CteScan))
 				show_ctescan_info(castNode(CteScanState, planstate), es);
+
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+				plan->applied_clauses_or,
+				planstate, ancestors, es);
 			break;
 		case T_Gather:
 			{
@@ -2224,6 +2251,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_TableFuncScan:
 			if (es->verbose)
@@ -2338,6 +2369,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_WindowAgg:
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
@@ -2354,6 +2389,10 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->applied_stats, plan->applied_clauses,
+								plan->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Sort:
 			show_sort_keys(castNode(SortState, planstate), ancestors, es);
@@ -2680,6 +2719,88 @@ show_scan_qual(List *qual, const char *qlabel,
 	show_qual(qual, qlabel, planstate, ancestors, useprefix, es);
 }
 
+/*
+ * Show a generic expression
+ */
+static char *
+deparse_stat_expression(Node *node,
+						PlanState *planstate, List *ancestors,
+						ExplainState *es)
+{
+	List	   *context;
+
+	/* Set up deparsing context */
+	context = set_deparse_context_plan(es->deparse_cxt,
+									   planstate->plan,
+									   ancestors);
+
+	/* Deparse the expression */
+	return deparse_expression(node, context, false, false);
+}
+
+/*
+ * Show a qualifier expression (which is a List with implicit AND semantics)
+ */
+static char *
+show_stat_qual(List *qual, int is_or,
+			   PlanState *planstate, List *ancestors,
+			   ExplainState *es)
+{
+	Node	   *node;
+
+	/* No work if empty qual */
+	if (qual == NIL)
+		return NULL;
+
+	/* Convert AND list to explicit AND */
+	switch (is_or)
+	{
+		case 0:
+			node = (Node *) make_ands_explicit(qual);
+			break;
+		case 1:
+			node = (Node *) make_ors_explicit(qual);
+			break;
+		case 2:
+			/* Extended stats for GROUP BY clause should be comma separeted string */
+			node = (Node *) qual;
+			break;
+		default:
+			elog(ERROR, "unexpected value: %d", is_or);
+			break;
+	}
+
+	/* And show it */
+	return deparse_stat_expression(node, planstate, ancestors, es);
+}
+
+/*
+ * Show applied statistics for scan/agg/group plan node
+ */
+static void
+show_scan_stats(List *stats, List *clauses, List *ors,
+				PlanState *planstate, List *ancestors, ExplainState *es)
+{
+	ListCell   *lc1, *lc2, *lc3;
+	StringInfoData	str;
+
+	forthree (lc1, stats, lc2, clauses, lc3, ors)
+	{
+		StatisticExtInfo   *stat = (StatisticExtInfo *) lfirst(lc1);
+		List   *applied_clauses = (List *) lfirst(lc2);
+		int		is_or = lfirst_int(lc3);
+
+		initStringInfo(&str);
+
+		appendStringInfo(&str, "%s.%s  Clauses: %s",
+						 get_namespace_name(get_statistics_namespace(stat->statOid)),
+						 get_statistics_name(stat->statOid),
+						 show_stat_qual(applied_clauses, is_or, planstate, ancestors, es));
+
+		ExplainPropertyText("Ext Stats", str.data, es);
+	}
+}
+
 /*
  * Show a qualifier expression for an upper-level plan node
  */
diff --git a/src/backend/nodes/makefuncs.c b/src/backend/nodes/makefuncs.c
index 9cac3c1c27..bcd81926e8 100644
--- a/src/backend/nodes/makefuncs.c
+++ b/src/backend/nodes/makefuncs.c
@@ -733,6 +733,17 @@ make_ands_explicit(List *andclauses)
 		return make_andclause(andclauses);
 }
 
+Expr *
+make_ors_explicit(List *orclauses)
+{
+	if (orclauses == NIL)
+		return (Expr *) makeBoolConst(true, false);
+	else if (list_length(orclauses) == 1)
+		return (Expr *) linitial(orclauses);
+	else
+		return make_orclause(orclauses);
+}
+
 List *
 make_ands_implicit(Expr *clause)
 {
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index f2ed0d81f6..a21a401c1b 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5452,6 +5452,8 @@ order_qual_clauses(PlannerInfo *root, List *clauses)
 static void
 copy_generic_path_info(Plan *dest, Path *src)
 {
+	ListCell *lc;
+
 	dest->disabled_nodes = src->disabled_nodes;
 	dest->startup_cost = src->startup_cost;
 	dest->total_cost = src->total_cost;
@@ -5459,6 +5461,19 @@ copy_generic_path_info(Plan *dest, Path *src)
 	dest->plan_width = src->pathtarget->width;
 	dest->parallel_aware = src->parallel_aware;
 	dest->parallel_safe = src->parallel_safe;
+
+	dest->applied_stats = src->parent->applied_stats;
+	dest->applied_clauses_or = src->parent->applied_clauses_or;
+
+	dest->applied_clauses = NIL;
+	foreach (lc, src->parent->applied_clauses)
+	{
+		List *clauses = (List *) lfirst(lc);
+
+		dest->applied_clauses
+			= lappend(dest->applied_clauses,
+					  maybe_extract_actual_clauses(clauses, false));
+	}
 }
 
 /*
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index d7266e4cdb..53ba64e731 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -287,6 +287,10 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 	rel->partexprs = NULL;
 	rel->nullable_partexprs = NULL;
 
+	rel->applied_stats = NIL;
+	rel->applied_clauses = NIL;
+	rel->applied_clauses_or = NIL;
+
 	/*
 	 * Pass assorted information down the inheritance hierarchy.
 	 */
@@ -769,6 +773,10 @@ build_join_rel(PlannerInfo *root,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to the foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
@@ -953,6 +961,10 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index 0b406e9334..23136a330b 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -508,6 +508,41 @@ extract_actual_clauses(List *restrictinfo_list,
 	return result;
 }
 
+/*
+ * maybe_extract_actual_clauses
+ *
+ * Just like extract_actual_clauses, but does not require the clauses to
+ * already be RestrictInfo.
+ *
+ * XXX Does not handle RestrictInfos nested in OR clauses.
+ */
+List *
+maybe_extract_actual_clauses(List *restrictinfo_list,
+							 bool pseudoconstant)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, restrictinfo_list)
+	{
+		RestrictInfo   *rinfo;
+		Node *node = (Node *) lfirst(l);
+
+		if (!IsA(node, RestrictInfo))
+		{
+			result = lappend(result, node);
+			continue;
+		}
+
+		rinfo = (RestrictInfo *) node;
+
+		if (rinfo->pseudoconstant == pseudoconstant)
+			result = lappend(result, rinfo->clause);
+	}
+
+	return result;
+}
+
 /*
  * extract_actual_join_clauses
  *
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index 99fdf208db..dbf921118e 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1857,6 +1857,14 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 			list_exprs[listidx] = NULL;
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, stat);
+			rel->applied_clauses = lappend(rel->applied_clauses, stat_clauses);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, (is_or) ? 1 : 0);
+		}
+
 		if (is_or)
 		{
 			bool	   *or_matches = NULL;
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 08fa6774d9..0a71685629 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4073,6 +4073,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 		ListCell   *lc2;
 		Bitmapset  *matched = NULL;
 		AttrNumber	attnum_offset;
+		List	   *matched_exprs = NIL;
 
 		/*
 		 * How much we need to offset the attnums? If there are no
@@ -4120,6 +4121,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 				matched = bms_add_member(matched, attnum);
 
+				/* track expressions matched by this statistics */
+				matched_exprs = lappend(matched_exprs, varinfo->var);
+
 				found = true;
 			}
 
@@ -4148,6 +4152,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 					matched = bms_add_member(matched, attnum);
 
+					/* track expressions matched by this statistics */
+					matched_exprs = lappend(matched_exprs, expr);
+
 					/* there should be just one matching expression */
 					break;
 				}
@@ -4156,6 +4163,14 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 			}
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, matched_info);
+			rel->applied_clauses = lappend(rel->applied_clauses, matched_exprs);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, 2); /* 2: Use comma to deparse */
+		}
+
 		/* Find the specific item that exactly matches the combination */
 		for (i = 0; i < stats->nitems; i++)
 		{
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index a85dc0d891..7368e82b62 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -35,6 +35,7 @@
 #include "catalog/pg_publication.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_subscription.h"
 #include "catalog/pg_transform.h"
 #include "catalog/pg_type.h"
@@ -3714,3 +3715,51 @@ get_subscription_name(Oid subid, bool missing_ok)
 
 	return subname;
 }
+
+/*
+ * get_statistics_name
+ *		Returns the name of a given extended statistics
+ *
+ * Returns a palloc'd copy of the string, or NULL if no such namespace.
+ */
+char *
+get_statistics_name(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		char	   *result;
+
+		result = pstrdup(NameStr(stxtup->stxname));
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return NULL;
+}
+
+/*
+ * get_statistics_namespace
+ *		Returns the namespace OID of a given extended statistics
+ */
+Oid
+get_statistics_namespace(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		Oid		result;
+
+		result = stxtup->stxnamespace;
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return InvalidOid;
+}
diff --git a/src/include/commands/explain.h b/src/include/commands/explain.h
index aa5872bc15..f06dcc0c3f 100644
--- a/src/include/commands/explain.h
+++ b/src/include/commands/explain.h
@@ -55,6 +55,7 @@ typedef struct ExplainState
 	bool		memory;			/* print planner's memory usage information */
 	bool		settings;		/* print modified settings */
 	bool		generic;		/* generate a generic plan */
+	bool		stats;			/* print applied extended stats */
 	ExplainSerializeOption serialize;	/* serialize the query's output? */
 	ExplainFormat format;		/* output format */
 	/* state for output formatting --- not reset for each new plan tree */
diff --git a/src/include/nodes/makefuncs.h b/src/include/nodes/makefuncs.h
index 0765e5c57b..05ef9f5f17 100644
--- a/src/include/nodes/makefuncs.h
+++ b/src/include/nodes/makefuncs.h
@@ -94,6 +94,8 @@ extern Node *make_and_qual(Node *qual1, Node *qual2);
 extern Expr *make_ands_explicit(List *andclauses);
 extern List *make_ands_implicit(Expr *clause);
 
+extern Expr *make_ors_explicit(List *orclauses);
+
 extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
 								List *expressions, List *predicates,
 								bool unique, bool nulls_not_distinct,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 0d96db5638..5364c0495d 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -240,6 +240,9 @@ typedef struct Query
 	ParseLoc	stmt_location;
 	/* length in bytes; 0 means "rest of string" */
 	ParseLoc	stmt_len pg_node_attr(query_jumble_ignore);
+
+	/* if true, query is explain with stats option */
+	bool        isExplain_Stats;
 } Query;
 
 
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index add0f9e45f..63b477b985 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1049,6 +1049,11 @@ typedef struct RelOptInfo
 	List	  **partexprs pg_node_attr(read_write_ignore);
 	/* Nullable partition key expressions */
 	List	  **nullable_partexprs pg_node_attr(read_write_ignore);
+
+	/* info about applied extended statistics */
+	List       *applied_stats;		/* list of StatisticExtInfo */
+	List       *applied_clauses;	/* list of lists of clauses */
+	List       *applied_clauses_or;	/* are the clauses AND, OR, or Comma */
 } RelOptInfo;
 
 /*
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 52f29bcdb6..03fa039f36 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -170,6 +170,11 @@ typedef struct Plan
 	 */
 	Bitmapset  *extParam;
 	Bitmapset  *allParam;
+
+	/* info about applied statistics */
+	List	   *applied_stats;
+	List	   *applied_clauses;
+	List	   *applied_clauses_or;
 } Plan;
 
 /* ----------------
diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index fe03a8ecd3..41bbb3231c 100644
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -39,6 +39,8 @@ extern bool restriction_is_securely_promotable(RestrictInfo *restrictinfo,
 extern List *get_actual_clauses(List *restrictinfo_list);
 extern List *extract_actual_clauses(List *restrictinfo_list,
 									bool pseudoconstant);
+extern List *maybe_extract_actual_clauses(List *restrictinfo_list,
+										  bool pseudoconstant);
 extern void extract_actual_join_clauses(List *restrictinfo_list,
 										Relids joinrelids,
 										List **joinquals,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 20446f6f83..3fab6d5eea 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -206,6 +206,9 @@ extern char *get_publication_name(Oid pubid, bool missing_ok);
 extern Oid	get_subscription_oid(const char *subname, bool missing_ok);
 extern char *get_subscription_name(Oid subid, bool missing_ok);
 
+extern char *get_statistics_name(Oid stxid);
+extern Oid	get_statistics_namespace(Oid stxid);
+
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
 #define type_is_array_domain(typid)  (get_base_element_type(typid) != InvalidOid)
-- 
2.43.5

diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 40c8462d680..bf2faa6d9f2 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -2738,6 +2738,25 @@ deparse_stat_expression(Node *node,
 	return deparse_expression(node, context, false, false);
 }
 
+static Node *
+strip_restrict_info_nodes(Node *node, void *context)
+{
+	if (node == NULL)
+		return NULL;
+
+	switch (nodeTag(node))
+	{
+		case T_RestrictInfo:
+			return (Node *) ((RestrictInfo *) node)->clause;
+
+		default:
+			break;
+	}
+
+	return expression_tree_mutator(node, strip_restrict_info_nodes,
+								   (void *) context);
+}
+
 /*
  * Show a qualifier expression (which is a List with implicit AND semantics)
  */
@@ -2752,6 +2771,10 @@ show_stat_qual(List *qual, int is_or,
 	if (qual == NIL)
 		return NULL;
 
+	/* remove all RestrictInfo nodes, which are not expected by deparsing */
+	qual = (List *) expression_tree_mutator((Node *) qual,
+											strip_restrict_info_nodes, NULL);
+
 	/* Convert AND list to explicit AND */
 	switch (is_or)
 	{

From a6bc82b5112cb424058b985c3028ca6b61d1c831 Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Mon, 10 Feb 2025 08:40:57 +0900
Subject: [PATCH 2/3] Add a new option auto_explain.log_stats to auto_explain
 (T9)

---
 contrib/auto_explain/auto_explain.c | 13 +++++++++++++
 doc/src/sgml/auto-explain.sgml      | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/contrib/auto_explain/auto_explain.c b/contrib/auto_explain/auto_explain.c
index f1ad876e821..564b7b5cdbb 100644
--- a/contrib/auto_explain/auto_explain.c
+++ b/contrib/auto_explain/auto_explain.c
@@ -29,6 +29,7 @@ static bool auto_explain_log_analyze = false;
 static bool auto_explain_log_verbose = false;
 static bool auto_explain_log_buffers = false;
 static bool auto_explain_log_wal = false;
+static bool auto_explain_log_stats = false;
 static bool auto_explain_log_triggers = false;
 static bool auto_explain_log_timing = true;
 static bool auto_explain_log_settings = false;
@@ -170,6 +171,17 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
+	DefineCustomBoolVariable("auto_explain.log_stats",
+							 "Use EXPLAIN STATS for plan logging.",
+							 NULL,
+							 &auto_explain_log_stats,
+							 false,
+							 PGC_SUSET,
+							 0,
+							 NULL,
+							 NULL,
+							 NULL);
+
 	DefineCustomBoolVariable("auto_explain.log_triggers",
 							 "Include trigger statistics in plans.",
 							 "This has no effect unless log_analyze is also set.",
@@ -396,6 +408,7 @@ explain_ExecutorEnd(QueryDesc *queryDesc)
 			es->summary = es->analyze;
 			/* No support for MEMORY */
 			/* es->memory = false; */
+			es->stats = auto_explain_log_stats;
 			es->format = auto_explain_log_format;
 			es->settings = auto_explain_log_settings;
 
diff --git a/doc/src/sgml/auto-explain.sgml b/doc/src/sgml/auto-explain.sgml
index 0c4656ee302..a3be3f38adc 100644
--- a/doc/src/sgml/auto-explain.sgml
+++ b/doc/src/sgml/auto-explain.sgml
@@ -148,6 +148,24 @@ LOAD 'auto_explain';
     </listitem>
    </varlistentry>
 
+   <varlistentry id="auto-explain-configuration-parameters-log-stats">
+    <term>
+     <varname>auto_explain.log_stats</varname> (<type>boolean</type>)
+     <indexterm>
+      <primary><varname>auto_explain.log_stats</varname> configuration parameter</primary>
+     </indexterm>
+    </term>
+    <listitem>
+     <para>
+      <varname>auto_explain.log_stats</varname> controls whether applied
+      Extended Statistic are printed when an execution plan is logged; it's
+      equivalent to the <literal>STATS</literal> option of <command>EXPLAIN</command>.
+      This parameter is off by default.
+      Only superusers can change this setting.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry id="auto-explain-configuration-parameters-log-timing">
     <term>
      <varname>auto_explain.log_timing</varname> (<type>boolean</type>)
-- 
2.43.5

From 972d5fdad76872480909cccc82bb32be759d452b Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Mon, 10 Feb 2025 08:41:58 +0900
Subject: [PATCH 3/3] Add a new tab completion for EXPLAIN (STATS) on psql (I2)

- When you run "EXPLAIN (<tab>" or "EXPLAIN (S<tab>" on psql,
  "STATS" string is displayed.
---
 src/bin/psql/tab-complete.in.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/bin/psql/tab-complete.in.c b/src/bin/psql/tab-complete.in.c
index 5f6897c8486..d4b504ebf31 100644
--- a/src/bin/psql/tab-complete.in.c
+++ b/src/bin/psql/tab-complete.in.c
@@ -4247,8 +4247,8 @@ match_previous_words(int pattern_id,
 		if (ends_with(prev_wd, '(') || ends_with(prev_wd, ','))
 			COMPLETE_WITH("ANALYZE", "VERBOSE", "COSTS", "SETTINGS", "GENERIC_PLAN",
 						  "BUFFERS", "SERIALIZE", "WAL", "TIMING", "SUMMARY",
-						  "MEMORY", "FORMAT");
-		else if (TailMatches("ANALYZE|VERBOSE|COSTS|SETTINGS|GENERIC_PLAN|BUFFERS|WAL|TIMING|SUMMARY|MEMORY"))
+						  "MEMORY", "FORMAT", "STATS");
+		else if (TailMatches("ANALYZE|VERBOSE|COSTS|SETTINGS|GENERIC_PLAN|BUFFERS|WAL|TIMING|SUMMARY|MEMORY|STATS"))
 			COMPLETE_WITH("ON", "OFF");
 		else if (TailMatches("SERIALIZE"))
 			COMPLETE_WITH("TEXT", "NONE", "BINARY");
-- 
2.43.5

From 82ba847cdbd1074b8f630827b20eedefc6a451b9 Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Mon, 10 Feb 2025 08:33:23 +0900
Subject: [PATCH 1/3] Add a new option STATS to EXPLAIN command

This patch allows to show applied extended statistics in EXPLAIN command output.
It includes the following points:

- Rebased on 9926f854

- Added a new struct Applied_ExtStats in plannode.h (T4)
    - Hopefully this will solve the issue related to "-DCOPY_PARSE_PLAN_TREES"
      with cfbot.
    - To pass the extended statistics information from path to plan,
      it might be more appropriate to define a new structure in primnode.h
      rather than plannode.h. Any advice would be appreciated.

- Handled EXPLAIN(STATS, VERBOSE) option (M2)
    - Before the fix, schema name was always added to extended statistics name,
      but with this patch, schema name is added to the following only when
      VERBOSE option is selected:
        - Extended statistics name, table name, and column name

- Added Supported extended statistics types in document (M4)
---
 doc/src/sgml/ref/explain.sgml             |  14 +++
 src/backend/commands/explain.c            | 140 ++++++++++++++++++++++
 src/backend/nodes/makefuncs.c             |  11 ++
 src/backend/optimizer/plan/createplan.c   |  17 +++
 src/backend/optimizer/util/relnode.c      |  12 ++
 src/backend/optimizer/util/restrictinfo.c |  35 ++++++
 src/backend/statistics/extended_stats.c   |   8 ++
 src/backend/utils/adt/selfuncs.c          |  15 +++
 src/backend/utils/cache/lsyscache.c       |  49 ++++++++
 src/include/commands/explain.h            |   1 +
 src/include/nodes/makefuncs.h             |   2 +
 src/include/nodes/parsenodes.h            |   3 +
 src/include/nodes/pathnodes.h             |   5 +
 src/include/nodes/plannodes.h             |  15 +++
 src/include/optimizer/restrictinfo.h      |   2 +
 src/include/utils/lsyscache.h             |   3 +
 16 files changed, 332 insertions(+)

diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index 6361a14e65d..176ff4b0f2f 100644
--- a/doc/src/sgml/ref/explain.sgml
+++ b/doc/src/sgml/ref/explain.sgml
@@ -43,6 +43,7 @@ EXPLAIN [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] <rep
     BUFFERS [ <replaceable class="parameter">boolean</replaceable> ]
     SERIALIZE [ { NONE | TEXT | BINARY } ]
     WAL [ <replaceable class="parameter">boolean</replaceable> ]
+    STATS [ <replaceable class="parameter">boolean</replaceable> ]
     TIMING [ <replaceable class="parameter">boolean</replaceable> ]
     SUMMARY [ <replaceable class="parameter">boolean</replaceable> ]
     MEMORY [ <replaceable class="parameter">boolean</replaceable> ]
@@ -250,6 +251,19 @@ ROLLBACK;
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>STATS</literal></term>
+    <listitem>
+     <para>
+      Include information on applied <literal>Extended statistics</literal>.
+      Specifically, include the names of extended statistics and clauses.
+      Supported extended statistics types are Dependencies and MCV.
+      See <xref linkend="planner-stats-extended"/> for details about extended
+      statistics. This parameter defaults to <literal>FALSE</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>TIMING</literal></term>
     <listitem>
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index c24e66f82e1..8aac5736864 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -94,6 +94,15 @@ static void show_qual(List *qual, const char *qlabel,
 static void show_scan_qual(List *qual, const char *qlabel,
 						   PlanState *planstate, List *ancestors,
 						   ExplainState *es);
+static char *deparse_stat_expression(Node *node,
+									 PlanState *planstate, List *ancestors,
+									 bool useprefix, ExplainState *es);
+static char *show_stat_qual(List *qual, int is_or,
+							PlanState *planstate, List *ancestors,
+							bool useprefix, ExplainState *es);
+static void show_scan_stats(List *stats, List *clauses, List *ors,
+							PlanState *planstate, List *ancestors,
+							ExplainState *es);
 static void show_upper_qual(List *qual, const char *qlabel,
 							PlanState *planstate, List *ancestors,
 							ExplainState *es);
@@ -223,6 +232,8 @@ ExplainQuery(ParseState *pstate, ExplainStmt *stmt,
 			es->settings = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "generic_plan") == 0)
 			es->generic = defGetBoolean(opt);
+		else if (strcmp(opt->defname, "stats") == 0)
+			es->stats = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "timing") == 0)
 		{
 			timing_set = true;
@@ -497,6 +508,11 @@ standard_ExplainOneQuery(Query *query, int cursorOptions,
 
 	if (es->buffers)
 		bufusage_start = pgBufferUsage;
+
+	/* if this flag is true, applied ext stats are stored */
+	if (es->stats)
+		query->isExplain_Stats = true;
+
 	INSTR_TIME_SET_CURRENT(planstart);
 
 	/* plan the query */
@@ -2114,6 +2130,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_IndexOnlyScan:
 			show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
@@ -2130,10 +2151,20 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (es->analyze)
 				ExplainPropertyFloat("Heap Fetches", NULL,
 									 planstate->instrument->ntuples2, 0, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapHeapScan:
 			show_scan_qual(((BitmapHeapScan *) plan)->bitmapqualorig,
@@ -2164,6 +2195,12 @@ ExplainNode(PlanState *planstate, List *ancestors,
 										   planstate, es);
 			if (IsA(plan, CteScan))
 				show_ctescan_info(castNode(CteScanState, planstate), es);
+
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Gather:
 			{
@@ -2231,6 +2268,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_TableFuncScan:
 			if (es->verbose)
@@ -2345,6 +2387,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_WindowAgg:
 			show_upper_qual(plan->qual, "Filter", planstate, ancestors, es);
@@ -2361,6 +2408,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Sort:
 			show_sort_keys(castNode(SortState, planstate), ancestors, es);
@@ -2687,6 +2739,94 @@ show_scan_qual(List *qual, const char *qlabel,
 	show_qual(qual, qlabel, planstate, ancestors, useprefix, es);
 }
 
+/*
+ * Show a generic expression
+ */
+static char *
+deparse_stat_expression(Node *node,
+						PlanState *planstate, List *ancestors,
+						bool useprefix, ExplainState *es)
+{
+	List	   *context;
+
+	/* Set up deparsing context */
+	context = set_deparse_context_plan(es->deparse_cxt,
+									   planstate->plan,
+									   ancestors);
+
+	/* Deparse the expression */
+	return deparse_expression(node, context, useprefix, false);
+}
+
+/*
+ * Show a qualifier expression for extended stats
+ */
+static char *
+show_stat_qual(List *qual, int is_or,
+			   PlanState *planstate, List *ancestors,
+			   bool useprefix, ExplainState *es)
+{
+	Node	   *node;
+
+	/* No work if empty qual */
+	if (qual == NIL)
+		return NULL;
+
+	/* Convert AND list to explicit AND */
+	switch (is_or)
+	{
+		case 0:
+			node = (Node *) make_ands_explicit(qual);
+			break;
+		case 1:
+			node = (Node *) make_ors_explicit(qual);
+			break;
+		case 2:
+			/* Extended stats for GROUP BY clause should be comma separeted string */
+			node = (Node *) qual;
+			break;
+		default:
+			elog(ERROR, "unexpected value: %d", is_or);
+			break;
+	}
+
+	/* And show it */
+	return deparse_stat_expression(node, planstate, ancestors, useprefix, es);
+}
+
+/*
+ * Show applied statistics for scan/agg/group plan node
+ */
+static void
+show_scan_stats(List *stats, List *clauses, List *ors,
+				PlanState *planstate, List *ancestors, ExplainState *es)
+{
+	ListCell   *lc1, *lc2, *lc3;
+	StringInfoData	str;
+	bool		useprefix;
+
+	useprefix = es->verbose;
+
+	forthree (lc1, stats, lc2, clauses, lc3, ors)
+	{
+		StatisticExtInfo   *stat = (StatisticExtInfo *) lfirst(lc1);
+		List   *applied_clauses = (List *) lfirst(lc2);
+		int		is_or = lfirst_int(lc3);
+
+		initStringInfo(&str);
+
+		if (useprefix)
+			appendStringInfo(&str, "%s.",
+							 get_namespace_name(get_statistics_namespace(stat->statOid)));
+
+		appendStringInfo(&str, "%s  Clauses: %s",
+						 get_statistics_name(stat->statOid),
+						 show_stat_qual(applied_clauses, is_or, planstate, ancestors, useprefix, es));
+
+		ExplainPropertyText("Ext Stats", str.data, es);
+	}
+}
+
 /*
  * Show a qualifier expression for an upper-level plan node
  */
diff --git a/src/backend/nodes/makefuncs.c b/src/backend/nodes/makefuncs.c
index 007612563ca..c09667a8b42 100644
--- a/src/backend/nodes/makefuncs.c
+++ b/src/backend/nodes/makefuncs.c
@@ -759,6 +759,17 @@ make_ands_explicit(List *andclauses)
 		return make_andclause(andclauses);
 }
 
+Expr *
+make_ors_explicit(List *orclauses)
+{
+	if (orclauses == NIL)
+		return (Expr *) makeBoolConst(true, false);
+	else if (list_length(orclauses) == 1)
+		return (Expr *) linitial(orclauses);
+	else
+		return make_orclause(orclauses);
+}
+
 List *
 make_ands_implicit(Expr *clause)
 {
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index 816a2b2a576..7a92799700e 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5455,6 +5455,8 @@ order_qual_clauses(PlannerInfo *root, List *clauses)
 static void
 copy_generic_path_info(Plan *dest, Path *src)
 {
+	ListCell *lc;
+
 	dest->disabled_nodes = src->disabled_nodes;
 	dest->startup_cost = src->startup_cost;
 	dest->total_cost = src->total_cost;
@@ -5462,6 +5464,21 @@ copy_generic_path_info(Plan *dest, Path *src)
 	dest->plan_width = src->pathtarget->width;
 	dest->parallel_aware = src->parallel_aware;
 	dest->parallel_safe = src->parallel_safe;
+
+	/* Is this the right place to use makeNode()? */
+	dest->app_extstats = makeNode(Applied_ExtStats);
+	dest->app_extstats->applied_stats = src->parent->applied_stats;
+	dest->app_extstats->applied_clauses_or = src->parent->applied_clauses_or;
+	dest->app_extstats->applied_clauses = NIL;
+
+	foreach (lc, src->parent->applied_clauses)
+	{
+		List *clauses = (List *) lfirst(lc);
+
+		dest->app_extstats->applied_clauses
+			= lappend(dest->app_extstats->applied_clauses,
+					  maybe_extract_actual_clauses(clauses, false));
+	}
 }
 
 /*
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index ff507331a06..b46ad85cba4 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -287,6 +287,10 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 	rel->partexprs = NULL;
 	rel->nullable_partexprs = NULL;
 
+	rel->applied_stats = NIL;
+	rel->applied_clauses = NIL;
+	rel->applied_clauses_or = NIL;
+
 	/*
 	 * Pass assorted information down the inheritance hierarchy.
 	 */
@@ -769,6 +773,10 @@ build_join_rel(PlannerInfo *root,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to the foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
@@ -953,6 +961,10 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index a80083d2323..b6cc5d7c2e2 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -499,6 +499,41 @@ extract_actual_clauses(List *restrictinfo_list,
 	return result;
 }
 
+/*
+ * maybe_extract_actual_clauses
+ *
+ * Just like extract_actual_clauses, but does not require the clauses to
+ * already be RestrictInfo.
+ *
+ * XXX Does not handle RestrictInfos nested in OR clauses.
+ */
+List *
+maybe_extract_actual_clauses(List *restrictinfo_list,
+							 bool pseudoconstant)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, restrictinfo_list)
+	{
+		RestrictInfo   *rinfo;
+		Node *node = (Node *) lfirst(l);
+
+		if (!IsA(node, RestrictInfo))
+		{
+			result = lappend(result, node);
+			continue;
+		}
+
+		rinfo = (RestrictInfo *) node;
+
+		if (rinfo->pseudoconstant == pseudoconstant)
+			result = lappend(result, rinfo->clause);
+	}
+
+	return result;
+}
+
 /*
  * extract_actual_join_clauses
  *
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index a8b63ec0884..c7367252aee 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1854,6 +1854,14 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 			list_exprs[listidx] = NULL;
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, stat);
+			rel->applied_clauses = lappend(rel->applied_clauses, stat_clauses);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, (is_or) ? 1 : 0);
+		}
+
 		if (is_or)
 		{
 			bool	   *or_matches = NULL;
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index d3d1e485bb2..3258a3517a3 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4083,6 +4083,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 		ListCell   *lc2;
 		Bitmapset  *matched = NULL;
 		AttrNumber	attnum_offset;
+		List	   *matched_exprs = NIL;
 
 		/*
 		 * How much we need to offset the attnums? If there are no
@@ -4130,6 +4131,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 				matched = bms_add_member(matched, attnum);
 
+				/* track expressions matched by this statistics */
+				matched_exprs = lappend(matched_exprs, varinfo->var);
+
 				found = true;
 			}
 
@@ -4158,6 +4162,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 					matched = bms_add_member(matched, attnum);
 
+					/* track expressions matched by this statistics */
+					matched_exprs = lappend(matched_exprs, expr);
+
 					/* there should be just one matching expression */
 					break;
 				}
@@ -4166,6 +4173,14 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 			}
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, matched_info);
+			rel->applied_clauses = lappend(rel->applied_clauses, matched_exprs);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, 2); /* 2: Use comma to deparse */
+		}
+
 		/* Find the specific item that exactly matches the combination */
 		for (i = 0; i < stats->nitems; i++)
 		{
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index bcfa5cb4add..36e3f72b041 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -36,6 +36,7 @@
 #include "catalog/pg_publication.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_subscription.h"
 #include "catalog/pg_transform.h"
 #include "catalog/pg_type.h"
@@ -3741,3 +3742,51 @@ get_subscription_name(Oid subid, bool missing_ok)
 
 	return subname;
 }
+
+/*
+ * get_statistics_name
+ *		Returns the name of a given extended statistics
+ *
+ * Returns a palloc'd copy of the string, or NULL if no such name.
+ */
+char *
+get_statistics_name(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		char	   *result;
+
+		result = pstrdup(NameStr(stxtup->stxname));
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return NULL;
+}
+
+/*
+ * get_statistics_namespace
+ *		Returns the namespace OID of a given extended statistics
+ */
+Oid
+get_statistics_namespace(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		Oid		result;
+
+		result = stxtup->stxnamespace;
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return InvalidOid;
+}
diff --git a/src/include/commands/explain.h b/src/include/commands/explain.h
index ea7419951f4..797075126a0 100644
--- a/src/include/commands/explain.h
+++ b/src/include/commands/explain.h
@@ -55,6 +55,7 @@ typedef struct ExplainState
 	bool		memory;			/* print planner's memory usage information */
 	bool		settings;		/* print modified settings */
 	bool		generic;		/* generate a generic plan */
+	bool		stats;			/* print applied extended stats */
 	ExplainSerializeOption serialize;	/* serialize the query's output? */
 	ExplainFormat format;		/* output format */
 	/* state for output formatting --- not reset for each new plan tree */
diff --git a/src/include/nodes/makefuncs.h b/src/include/nodes/makefuncs.h
index 5473ce9a288..b32aa762c9b 100644
--- a/src/include/nodes/makefuncs.h
+++ b/src/include/nodes/makefuncs.h
@@ -95,6 +95,8 @@ extern Node *make_and_qual(Node *qual1, Node *qual2);
 extern Expr *make_ands_explicit(List *andclauses);
 extern List *make_ands_implicit(Expr *clause);
 
+extern Expr *make_ors_explicit(List *orclauses);
+
 extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
 								List *expressions, List *predicates,
 								bool unique, bool nulls_not_distinct,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 8dd421fa0ef..27b48629e66 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -249,6 +249,9 @@ typedef struct Query
 	ParseLoc	stmt_location;
 	/* length in bytes; 0 means "rest of string" */
 	ParseLoc	stmt_len pg_node_attr(query_jumble_ignore);
+
+	/* if true, query is explain with stats option */
+	bool        isExplain_Stats;
 } Query;
 
 
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index 00c700cc3e7..569d876fdfe 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1068,6 +1068,11 @@ typedef struct RelOptInfo
 	List	  **partexprs pg_node_attr(read_write_ignore);
 	/* Nullable partition key expressions */
 	List	  **nullable_partexprs pg_node_attr(read_write_ignore);
+
+	/* info about applied extended statistics */
+	List       *applied_stats;		/* list of StatisticExtInfo */
+	List       *applied_clauses;	/* list of lists of clauses */
+	List       *applied_clauses_or;	/* are the clauses AND, OR, or Comma */
 } RelOptInfo;
 
 /*
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 2a2cf816cb6..39d2d131348 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -177,6 +177,9 @@ typedef struct Plan
 	 */
 	Bitmapset  *extParam;
 	Bitmapset  *allParam;
+
+	/* info about applied extended statistics */
+	struct Applied_ExtStats *app_extstats;
 } Plan;
 
 /* ----------------
@@ -1617,4 +1620,16 @@ typedef enum MonotonicFunction
 	MONOTONICFUNC_BOTH = MONOTONICFUNC_INCREASING | MONOTONICFUNC_DECREASING,
 } MonotonicFunction;
 
+/*
+ * Applied_ExtStats - Information to show applied Extend Statistics
+ *
+ */
+typedef struct Applied_ExtStats
+{
+	NodeTag	type;
+	List    *applied_stats;
+	List    *applied_clauses;
+	List    *applied_clauses_or;
+} Applied_ExtStats;
+
 #endif							/* PLANNODES_H */
diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index ec91fc9c583..0c34af43138 100644
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -50,6 +50,8 @@ extern bool restriction_is_securely_promotable(RestrictInfo *restrictinfo,
 extern List *get_actual_clauses(List *restrictinfo_list);
 extern List *extract_actual_clauses(List *restrictinfo_list,
 									bool pseudoconstant);
+extern List *maybe_extract_actual_clauses(List *restrictinfo_list,
+										  bool pseudoconstant);
 extern void extract_actual_join_clauses(List *restrictinfo_list,
 										Relids joinrelids,
 										List **joinquals,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index 6fab7aa6009..f1e73e389c8 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -207,6 +207,9 @@ extern char *get_publication_name(Oid pubid, bool missing_ok);
 extern Oid	get_subscription_oid(const char *subname, bool missing_ok);
 extern char *get_subscription_name(Oid subid, bool missing_ok);
 
+extern char *get_statistics_name(Oid stxid);
+extern Oid	get_statistics_namespace(Oid stxid);
+
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
 #define type_is_array_domain(typid)  (get_base_element_type(typid) != InvalidOid)
-- 
2.43.5

From ff2cc418d59bd32e92617fca6f8c2f5f8f4951ad Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Mon, 10 Feb 2025 08:33:23 +0900
Subject: [PATCH 1/3] Add a new option STATS to EXPLAIN command

This patch allows to show applied extended statistics in EXPLAIN command output.
It includes the following points:

- Rebased on 9926f854

- Added a new struct Applied_ExtStats in plannode.h (T4)
    - Hopefully this will solve the issue related to "-DCOPY_PARSE_PLAN_TREES"
      with cfbot.
    - To pass the extended statistics information from path to plan,
      it might be more appropriate to define a new structure in primnode.h
      rather than plannode.h. Any advice would be appreciated.

- Handled EXPLAIN(STATS, VERBOSE) option (M2)
    - Before the fix, schema name was always added to extended statistics name,
      but with this patch, schema name is added to the following only when
      VERBOSE option is selected:
        - Extended statistics name, table name, and column name

- Added Supported extended statistics types in document (M4)
---
 doc/src/sgml/ref/explain.sgml             |  14 +++
 src/backend/commands/explain.c            | 138 ++++++++++++++++++++++
 src/backend/commands/explain_state.c      |   2 +
 src/backend/nodes/makefuncs.c             |  11 ++
 src/backend/optimizer/plan/createplan.c   |  17 +++
 src/backend/optimizer/util/relnode.c      |  12 ++
 src/backend/optimizer/util/restrictinfo.c |  35 ++++++
 src/backend/statistics/extended_stats.c   |   8 ++
 src/backend/utils/adt/selfuncs.c          |  15 +++
 src/backend/utils/cache/lsyscache.c       |  49 ++++++++
 src/include/commands/explain_state.h      |   1 +
 src/include/nodes/makefuncs.h             |   2 +
 src/include/nodes/parsenodes.h            |   3 +
 src/include/nodes/pathnodes.h             |   5 +
 src/include/nodes/plannodes.h             |  15 +++
 src/include/optimizer/restrictinfo.h      |   2 +
 src/include/utils/lsyscache.h             |   3 +
 17 files changed, 332 insertions(+)

diff --git a/doc/src/sgml/ref/explain.sgml b/doc/src/sgml/ref/explain.sgml
index 6dda680aa0d..6bfe694dae8 100644
--- a/doc/src/sgml/ref/explain.sgml
+++ b/doc/src/sgml/ref/explain.sgml
@@ -43,6 +43,7 @@ EXPLAIN [ ( <replaceable class="parameter">option</replaceable> [, ...] ) ] <rep
     BUFFERS [ <replaceable class="parameter">boolean</replaceable> ]
     SERIALIZE [ { NONE | TEXT | BINARY } ]
     WAL [ <replaceable class="parameter">boolean</replaceable> ]
+    STATS [ <replaceable class="parameter">boolean</replaceable> ]
     TIMING [ <replaceable class="parameter">boolean</replaceable> ]
     SUMMARY [ <replaceable class="parameter">boolean</replaceable> ]
     MEMORY [ <replaceable class="parameter">boolean</replaceable> ]
@@ -249,6 +250,19 @@ ROLLBACK;
     </listitem>
    </varlistentry>
 
+   <varlistentry>
+    <term><literal>STATS</literal></term>
+    <listitem>
+     <para>
+      Include information on applied <literal>Extended statistics</literal>.
+      Specifically, include the names of extended statistics and clauses.
+      Supported extended statistics types are Dependencies and MCV.
+      See <xref linkend="planner-stats-extended"/> for details about extended
+      statistics. This parameter defaults to <literal>FALSE</literal>.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry>
     <term><literal>TIMING</literal></term>
     <listitem>
diff --git a/src/backend/commands/explain.c b/src/backend/commands/explain.c
index 8345bc0264b..53593775939 100644
--- a/src/backend/commands/explain.c
+++ b/src/backend/commands/explain.c
@@ -87,6 +87,15 @@ static void show_qual(List *qual, const char *qlabel,
 static void show_scan_qual(List *qual, const char *qlabel,
 						   PlanState *planstate, List *ancestors,
 						   ExplainState *es);
+static char *deparse_stat_expression(Node *node,
+									 PlanState *planstate, List *ancestors,
+									 bool useprefix, ExplainState *es);
+static char *show_stat_qual(List *qual, int is_or,
+							PlanState *planstate, List *ancestors,
+							bool useprefix, ExplainState *es);
+static void show_scan_stats(List *stats, List *clauses, List *ors,
+							PlanState *planstate, List *ancestors,
+							ExplainState *es);
 static void show_upper_qual(List *qual, const char *qlabel,
 							PlanState *planstate, List *ancestors,
 							ExplainState *es);
@@ -347,6 +356,11 @@ standard_ExplainOneQuery(Query *query, int cursorOptions,
 
 	if (es->buffers)
 		bufusage_start = pgBufferUsage;
+
+	/* if this flag is true, applied ext stats are stored */
+	if (es->stats)
+		query->isExplain_Stats = true;
+
 	INSTR_TIME_SET_CURRENT(planstart);
 
 	/* plan the query */
@@ -1966,6 +1980,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
 			show_indexsearches_info(planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_IndexOnlyScan:
 			show_scan_qual(((IndexOnlyScan *) plan)->indexqual,
@@ -1983,11 +2002,21 @@ ExplainNode(PlanState *planstate, List *ancestors,
 				ExplainPropertyFloat("Heap Fetches", NULL,
 									 planstate->instrument->ntuples2, 0, es);
 			show_indexsearches_info(planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapIndexScan:
 			show_scan_qual(((BitmapIndexScan *) plan)->indexqualorig,
 						   "Index Cond", planstate, ancestors, es);
 			show_indexsearches_info(planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_BitmapHeapScan:
 			show_scan_qual(((BitmapHeapScan *) plan)->bitmapqualorig,
@@ -2018,6 +2047,12 @@ ExplainNode(PlanState *planstate, List *ancestors,
 										   planstate, es);
 			if (IsA(plan, CteScan))
 				show_ctescan_info(castNode(CteScanState, planstate), es);
+
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Gather:
 			{
@@ -2085,6 +2120,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_TableFuncScan:
 			if (es->verbose)
@@ -2199,6 +2239,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_WindowAgg:
 			show_window_def(castNode(WindowAggState, planstate), ancestors, es);
@@ -2216,6 +2261,11 @@ ExplainNode(PlanState *planstate, List *ancestors,
 			if (plan->qual)
 				show_instrumentation_count("Rows Removed by Filter", 1,
 										   planstate, es);
+			if (es->stats)
+				show_scan_stats(plan->app_extstats->applied_stats,
+								plan->app_extstats->applied_clauses,
+								plan->app_extstats->applied_clauses_or,
+								planstate, ancestors, es);
 			break;
 		case T_Sort:
 			show_sort_keys(castNode(SortState, planstate), ancestors, es);
@@ -2547,6 +2597,94 @@ show_scan_qual(List *qual, const char *qlabel,
 	show_qual(qual, qlabel, planstate, ancestors, useprefix, es);
 }
 
+/*
+ * Show a generic expression
+ */
+static char *
+deparse_stat_expression(Node *node,
+						PlanState *planstate, List *ancestors,
+						bool useprefix, ExplainState *es)
+{
+	List	   *context;
+
+	/* Set up deparsing context */
+	context = set_deparse_context_plan(es->deparse_cxt,
+									   planstate->plan,
+									   ancestors);
+
+	/* Deparse the expression */
+	return deparse_expression(node, context, useprefix, false);
+}
+
+/*
+ * Show a qualifier expression for extended stats
+ */
+static char *
+show_stat_qual(List *qual, int is_or,
+			   PlanState *planstate, List *ancestors,
+			   bool useprefix, ExplainState *es)
+{
+	Node	   *node;
+
+	/* No work if empty qual */
+	if (qual == NIL)
+		return NULL;
+
+	/* Convert AND list to explicit AND */
+	switch (is_or)
+	{
+		case 0:
+			node = (Node *) make_ands_explicit(qual);
+			break;
+		case 1:
+			node = (Node *) make_ors_explicit(qual);
+			break;
+		case 2:
+			/* Extended stats for GROUP BY clause should be comma separeted string */
+			node = (Node *) qual;
+			break;
+		default:
+			elog(ERROR, "unexpected value: %d", is_or);
+			break;
+	}
+
+	/* And show it */
+	return deparse_stat_expression(node, planstate, ancestors, useprefix, es);
+}
+
+/*
+ * Show applied statistics for scan/agg/group plan node
+ */
+static void
+show_scan_stats(List *stats, List *clauses, List *ors,
+				PlanState *planstate, List *ancestors, ExplainState *es)
+{
+	ListCell   *lc1, *lc2, *lc3;
+	StringInfoData	str;
+	bool		useprefix;
+
+	useprefix = es->verbose;
+
+	forthree (lc1, stats, lc2, clauses, lc3, ors)
+	{
+		StatisticExtInfo   *stat = (StatisticExtInfo *) lfirst(lc1);
+		List   *applied_clauses = (List *) lfirst(lc2);
+		int		is_or = lfirst_int(lc3);
+
+		initStringInfo(&str);
+
+		if (useprefix)
+			appendStringInfo(&str, "%s.",
+							 get_namespace_name(get_statistics_namespace(stat->statOid)));
+
+		appendStringInfo(&str, "%s  Clauses: %s",
+						 get_statistics_name(stat->statOid),
+						 show_stat_qual(applied_clauses, is_or, planstate, ancestors, useprefix, es));
+
+		ExplainPropertyText("Ext Stats", str.data, es);
+	}
+}
+
 /*
  * Show a qualifier expression for an upper-level plan node
  */
diff --git a/src/backend/commands/explain_state.c b/src/backend/commands/explain_state.c
index 60d98d63a62..5d1ff461a7d 100644
--- a/src/backend/commands/explain_state.c
+++ b/src/backend/commands/explain_state.c
@@ -103,6 +103,8 @@ ParseExplainOptionList(ExplainState *es, List *options, ParseState *pstate)
 			es->settings = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "generic_plan") == 0)
 			es->generic = defGetBoolean(opt);
+		else if (strcmp(opt->defname, "stats") == 0)
+			es->stats = defGetBoolean(opt);
 		else if (strcmp(opt->defname, "timing") == 0)
 		{
 			timing_set = true;
diff --git a/src/backend/nodes/makefuncs.c b/src/backend/nodes/makefuncs.c
index e2d9e9be41a..fe021f35e05 100644
--- a/src/backend/nodes/makefuncs.c
+++ b/src/backend/nodes/makefuncs.c
@@ -806,6 +806,17 @@ make_ands_explicit(List *andclauses)
 		return make_andclause(andclauses);
 }
 
+Expr *
+make_ors_explicit(List *orclauses)
+{
+	if (orclauses == NIL)
+		return (Expr *) makeBoolConst(true, false);
+	else if (list_length(orclauses) == 1)
+		return (Expr *) linitial(orclauses);
+	else
+		return make_orclause(orclauses);
+}
+
 List *
 make_ands_implicit(Expr *clause)
 {
diff --git a/src/backend/optimizer/plan/createplan.c b/src/backend/optimizer/plan/createplan.c
index bfefc7dbea1..fbcf64ef264 100644
--- a/src/backend/optimizer/plan/createplan.c
+++ b/src/backend/optimizer/plan/createplan.c
@@ -5561,6 +5561,8 @@ order_qual_clauses(PlannerInfo *root, List *clauses)
 static void
 copy_generic_path_info(Plan *dest, Path *src)
 {
+	ListCell *lc;
+
 	dest->disabled_nodes = src->disabled_nodes;
 	dest->startup_cost = src->startup_cost;
 	dest->total_cost = src->total_cost;
@@ -5568,6 +5570,21 @@ copy_generic_path_info(Plan *dest, Path *src)
 	dest->plan_width = src->pathtarget->width;
 	dest->parallel_aware = src->parallel_aware;
 	dest->parallel_safe = src->parallel_safe;
+
+	/* Is this the right place to use makeNode()? */
+	dest->app_extstats = makeNode(Applied_ExtStats);
+	dest->app_extstats->applied_stats = src->parent->applied_stats;
+	dest->app_extstats->applied_clauses_or = src->parent->applied_clauses_or;
+	dest->app_extstats->applied_clauses = NIL;
+
+	foreach (lc, src->parent->applied_clauses)
+	{
+		List *clauses = (List *) lfirst(lc);
+
+		dest->app_extstats->applied_clauses
+			= lappend(dest->app_extstats->applied_clauses,
+					  maybe_extract_actual_clauses(clauses, false));
+	}
 }
 
 /*
diff --git a/src/backend/optimizer/util/relnode.c b/src/backend/optimizer/util/relnode.c
index ff507331a06..b46ad85cba4 100644
--- a/src/backend/optimizer/util/relnode.c
+++ b/src/backend/optimizer/util/relnode.c
@@ -287,6 +287,10 @@ build_simple_rel(PlannerInfo *root, int relid, RelOptInfo *parent)
 	rel->partexprs = NULL;
 	rel->nullable_partexprs = NULL;
 
+	rel->applied_stats = NIL;
+	rel->applied_clauses = NIL;
+	rel->applied_clauses_or = NIL;
+
 	/*
 	 * Pass assorted information down the inheritance hierarchy.
 	 */
@@ -769,6 +773,10 @@ build_join_rel(PlannerInfo *root,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to the foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
@@ -953,6 +961,10 @@ build_child_join_rel(PlannerInfo *root, RelOptInfo *outer_rel,
 	joinrel->partexprs = NULL;
 	joinrel->nullable_partexprs = NULL;
 
+	joinrel->applied_stats = NIL;
+	joinrel->applied_clauses = NIL;
+	joinrel->applied_clauses_or = NIL;
+
 	/* Compute information relevant to foreign relations. */
 	set_foreign_rel_properties(joinrel, outer_rel, inner_rel);
 
diff --git a/src/backend/optimizer/util/restrictinfo.c b/src/backend/optimizer/util/restrictinfo.c
index a80083d2323..b6cc5d7c2e2 100644
--- a/src/backend/optimizer/util/restrictinfo.c
+++ b/src/backend/optimizer/util/restrictinfo.c
@@ -499,6 +499,41 @@ extract_actual_clauses(List *restrictinfo_list,
 	return result;
 }
 
+/*
+ * maybe_extract_actual_clauses
+ *
+ * Just like extract_actual_clauses, but does not require the clauses to
+ * already be RestrictInfo.
+ *
+ * XXX Does not handle RestrictInfos nested in OR clauses.
+ */
+List *
+maybe_extract_actual_clauses(List *restrictinfo_list,
+							 bool pseudoconstant)
+{
+	List	   *result = NIL;
+	ListCell   *l;
+
+	foreach(l, restrictinfo_list)
+	{
+		RestrictInfo   *rinfo;
+		Node *node = (Node *) lfirst(l);
+
+		if (!IsA(node, RestrictInfo))
+		{
+			result = lappend(result, node);
+			continue;
+		}
+
+		rinfo = (RestrictInfo *) node;
+
+		if (rinfo->pseudoconstant == pseudoconstant)
+			result = lappend(result, rinfo->clause);
+	}
+
+	return result;
+}
+
 /*
  * extract_actual_join_clauses
  *
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index a8b63ec0884..c7367252aee 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1854,6 +1854,14 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 			list_exprs[listidx] = NULL;
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, stat);
+			rel->applied_clauses = lappend(rel->applied_clauses, stat_clauses);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, (is_or) ? 1 : 0);
+		}
+
 		if (is_or)
 		{
 			bool	   *or_matches = NULL;
diff --git a/src/backend/utils/adt/selfuncs.c b/src/backend/utils/adt/selfuncs.c
index 17fbfa9b410..e90937bec55 100644
--- a/src/backend/utils/adt/selfuncs.c
+++ b/src/backend/utils/adt/selfuncs.c
@@ -4346,6 +4346,7 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 		ListCell   *lc2;
 		Bitmapset  *matched = NULL;
 		AttrNumber	attnum_offset;
+		List	   *matched_exprs = NIL;
 
 		/*
 		 * How much we need to offset the attnums? If there are no
@@ -4393,6 +4394,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 				matched = bms_add_member(matched, attnum);
 
+				/* track expressions matched by this statistics */
+				matched_exprs = lappend(matched_exprs, varinfo->var);
+
 				found = true;
 			}
 
@@ -4421,6 +4425,9 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 
 					matched = bms_add_member(matched, attnum);
 
+					/* track expressions matched by this statistics */
+					matched_exprs = lappend(matched_exprs, expr);
+
 					/* there should be just one matching expression */
 					break;
 				}
@@ -4429,6 +4436,14 @@ estimate_multivariate_ndistinct(PlannerInfo *root, RelOptInfo *rel,
 			}
 		}
 
+		/* add it to the list of applied stats/clauses, if this flag is true */
+		if (root->parse->isExplain_Stats)
+		{
+			rel->applied_stats = lappend(rel->applied_stats, matched_info);
+			rel->applied_clauses = lappend(rel->applied_clauses, matched_exprs);
+			rel->applied_clauses_or = lappend_int(rel->applied_clauses_or, 2); /* 2: Use comma to deparse */
+		}
+
 		/* Find the specific item that exactly matches the combination */
 		for (i = 0; i < stats->nitems; i++)
 		{
diff --git a/src/backend/utils/cache/lsyscache.c b/src/backend/utils/cache/lsyscache.c
index c460a72b75d..562ee4a8f9c 100644
--- a/src/backend/utils/cache/lsyscache.c
+++ b/src/backend/utils/cache/lsyscache.c
@@ -36,6 +36,7 @@
 #include "catalog/pg_publication.h"
 #include "catalog/pg_range.h"
 #include "catalog/pg_statistic.h"
+#include "catalog/pg_statistic_ext.h"
 #include "catalog/pg_subscription.h"
 #include "catalog/pg_transform.h"
 #include "catalog/pg_type.h"
@@ -3854,3 +3855,51 @@ get_subscription_name(Oid subid, bool missing_ok)
 
 	return subname;
 }
+
+/*
+ * get_statistics_name
+ *		Returns the name of a given extended statistics
+ *
+ * Returns a palloc'd copy of the string, or NULL if no such name.
+ */
+char *
+get_statistics_name(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		char	   *result;
+
+		result = pstrdup(NameStr(stxtup->stxname));
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return NULL;
+}
+
+/*
+ * get_statistics_namespace
+ *		Returns the namespace OID of a given extended statistics
+ */
+Oid
+get_statistics_namespace(Oid stxid)
+{
+	HeapTuple	tp;
+
+	tp = SearchSysCache1(STATEXTOID, ObjectIdGetDatum(stxid));
+	if (HeapTupleIsValid(tp))
+	{
+		Form_pg_statistic_ext stxtup = (Form_pg_statistic_ext) GETSTRUCT(tp);
+		Oid		result;
+
+		result = stxtup->stxnamespace;
+		ReleaseSysCache(tp);
+		return result;
+	}
+	else
+		return InvalidOid;
+}
diff --git a/src/include/commands/explain_state.h b/src/include/commands/explain_state.h
index 32728f5d1a1..10b4103db83 100644
--- a/src/include/commands/explain_state.h
+++ b/src/include/commands/explain_state.h
@@ -55,6 +55,7 @@ typedef struct ExplainState
 	bool		memory;			/* print planner's memory usage information */
 	bool		settings;		/* print modified settings */
 	bool		generic;		/* generate a generic plan */
+	bool		stats;			/* print applied extended stats */
 	ExplainSerializeOption serialize;	/* serialize the query's output? */
 	ExplainFormat format;		/* output format */
 	/* state for output formatting --- not reset for each new plan tree */
diff --git a/src/include/nodes/makefuncs.h b/src/include/nodes/makefuncs.h
index 5473ce9a288..b32aa762c9b 100644
--- a/src/include/nodes/makefuncs.h
+++ b/src/include/nodes/makefuncs.h
@@ -95,6 +95,8 @@ extern Node *make_and_qual(Node *qual1, Node *qual2);
 extern Expr *make_ands_explicit(List *andclauses);
 extern List *make_ands_implicit(Expr *clause);
 
+extern Expr *make_ors_explicit(List *orclauses);
+
 extern IndexInfo *makeIndexInfo(int numattrs, int numkeyattrs, Oid amoid,
 								List *expressions, List *predicates,
 								bool unique, bool nulls_not_distinct,
diff --git a/src/include/nodes/parsenodes.h b/src/include/nodes/parsenodes.h
index 86a236bd58b..acadd843d69 100644
--- a/src/include/nodes/parsenodes.h
+++ b/src/include/nodes/parsenodes.h
@@ -254,6 +254,9 @@ typedef struct Query
 	ParseLoc	stmt_location;
 	/* length in bytes; 0 means "rest of string" */
 	ParseLoc	stmt_len pg_node_attr(query_jumble_ignore);
+
+	/* if true, query is explain with stats option */
+	bool        isExplain_Stats;
 } Query;
 
 
diff --git a/src/include/nodes/pathnodes.h b/src/include/nodes/pathnodes.h
index ad2726f026f..081546cc771 100644
--- a/src/include/nodes/pathnodes.h
+++ b/src/include/nodes/pathnodes.h
@@ -1075,6 +1075,11 @@ typedef struct RelOptInfo
 	List	  **partexprs pg_node_attr(read_write_ignore);
 	/* Nullable partition key expressions */
 	List	  **nullable_partexprs pg_node_attr(read_write_ignore);
+
+	/* info about applied extended statistics */
+	List       *applied_stats;		/* list of StatisticExtInfo */
+	List       *applied_clauses;	/* list of lists of clauses */
+	List       *applied_clauses_or;	/* are the clauses AND, OR, or Comma */
 } RelOptInfo;
 
 /*
diff --git a/src/include/nodes/plannodes.h b/src/include/nodes/plannodes.h
index 29d7732d6a0..aba7b29eb21 100644
--- a/src/include/nodes/plannodes.h
+++ b/src/include/nodes/plannodes.h
@@ -239,6 +239,9 @@ typedef struct Plan
 	 */
 	Bitmapset  *extParam;
 	Bitmapset  *allParam;
+
+	/* info about applied extended statistics */
+	struct Applied_ExtStats *app_extstats;
 } Plan;
 
 /* ----------------
@@ -1792,4 +1795,16 @@ typedef enum MonotonicFunction
 	MONOTONICFUNC_BOTH = MONOTONICFUNC_INCREASING | MONOTONICFUNC_DECREASING,
 } MonotonicFunction;
 
+/*
+ * Applied_ExtStats - Information to show applied Extend Statistics
+ *
+ */
+typedef struct Applied_ExtStats
+{
+	NodeTag	type;
+	List    *applied_stats;
+	List    *applied_clauses;
+	List    *applied_clauses_or;
+} Applied_ExtStats;
+
 #endif							/* PLANNODES_H */
diff --git a/src/include/optimizer/restrictinfo.h b/src/include/optimizer/restrictinfo.h
index ec91fc9c583..0c34af43138 100644
--- a/src/include/optimizer/restrictinfo.h
+++ b/src/include/optimizer/restrictinfo.h
@@ -50,6 +50,8 @@ extern bool restriction_is_securely_promotable(RestrictInfo *restrictinfo,
 extern List *get_actual_clauses(List *restrictinfo_list);
 extern List *extract_actual_clauses(List *restrictinfo_list,
 									bool pseudoconstant);
+extern List *maybe_extract_actual_clauses(List *restrictinfo_list,
+										  bool pseudoconstant);
 extern void extract_actual_join_clauses(List *restrictinfo_list,
 										Relids joinrelids,
 										List **joinquals,
diff --git a/src/include/utils/lsyscache.h b/src/include/utils/lsyscache.h
index fa7c7e0323b..88b8f9c1bd6 100644
--- a/src/include/utils/lsyscache.h
+++ b/src/include/utils/lsyscache.h
@@ -211,6 +211,9 @@ extern char *get_publication_name(Oid pubid, bool missing_ok);
 extern Oid	get_subscription_oid(const char *subname, bool missing_ok);
 extern char *get_subscription_name(Oid subid, bool missing_ok);
 
+extern char *get_statistics_name(Oid stxid);
+extern Oid	get_statistics_namespace(Oid stxid);
+
 #define type_is_array(typid)  (get_element_type(typid) != InvalidOid)
 /* type_is_array_domain accepts both plain arrays and domains over arrays */
 #define type_is_array_domain(typid)  (get_base_element_type(typid) != InvalidOid)
-- 
2.39.5

From 253a6906eb3ed19d8de2b089fa581710fd9886a5 Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Mon, 10 Feb 2025 08:40:57 +0900
Subject: [PATCH 2/3] Add a new option auto_explain.log_stats to auto_explain
 (T9)

---
 contrib/auto_explain/auto_explain.c | 13 +++++++++++++
 doc/src/sgml/auto-explain.sgml      | 18 ++++++++++++++++++
 2 files changed, 31 insertions(+)

diff --git a/contrib/auto_explain/auto_explain.c b/contrib/auto_explain/auto_explain.c
index 1f4badb4928..20fbcc69025 100644
--- a/contrib/auto_explain/auto_explain.c
+++ b/contrib/auto_explain/auto_explain.c
@@ -34,6 +34,7 @@ static bool auto_explain_log_analyze = false;
 static bool auto_explain_log_verbose = false;
 static bool auto_explain_log_buffers = false;
 static bool auto_explain_log_wal = false;
+static bool auto_explain_log_stats = false;
 static bool auto_explain_log_triggers = false;
 static bool auto_explain_log_timing = true;
 static bool auto_explain_log_settings = false;
@@ -175,6 +176,17 @@ _PG_init(void)
 							 NULL,
 							 NULL);
 
+	DefineCustomBoolVariable("auto_explain.log_stats",
+							 "Use EXPLAIN STATS for plan logging.",
+							 NULL,
+							 &auto_explain_log_stats,
+							 false,
+							 PGC_SUSET,
+							 0,
+							 NULL,
+							 NULL,
+							 NULL);
+
 	DefineCustomBoolVariable("auto_explain.log_triggers",
 							 "Include trigger statistics in plans.",
 							 "This has no effect unless log_analyze is also set.",
@@ -401,6 +413,7 @@ explain_ExecutorEnd(QueryDesc *queryDesc)
 			es->summary = es->analyze;
 			/* No support for MEMORY */
 			/* es->memory = false; */
+			es->stats = auto_explain_log_stats;
 			es->format = auto_explain_log_format;
 			es->settings = auto_explain_log_settings;
 
diff --git a/doc/src/sgml/auto-explain.sgml b/doc/src/sgml/auto-explain.sgml
index 15c868021e6..96599b12f3b 100644
--- a/doc/src/sgml/auto-explain.sgml
+++ b/doc/src/sgml/auto-explain.sgml
@@ -148,6 +148,24 @@ LOAD 'auto_explain';
     </listitem>
    </varlistentry>
 
+   <varlistentry id="auto-explain-configuration-parameters-log-stats">
+    <term>
+     <varname>auto_explain.log_stats</varname> (<type>boolean</type>)
+     <indexterm>
+      <primary><varname>auto_explain.log_stats</varname> configuration parameter</primary>
+     </indexterm>
+    </term>
+    <listitem>
+     <para>
+      <varname>auto_explain.log_stats</varname> controls whether applied
+      Extended Statistic are printed when an execution plan is logged; it's
+      equivalent to the <literal>STATS</literal> option of <command>EXPLAIN</command>.
+      This parameter is off by default.
+      Only superusers can change this setting.
+     </para>
+    </listitem>
+   </varlistentry>
+
    <varlistentry id="auto-explain-configuration-parameters-log-timing">
     <term>
      <varname>auto_explain.log_timing</varname> (<type>boolean</type>)
-- 
2.39.5

From c8cc8de12f1830fd5b6659c98c2764f1a2e405c8 Mon Sep 17 00:00:00 2001
From: Tatsuro Yamada <yamatattsu@gmail.com>
Date: Mon, 10 Feb 2025 08:41:58 +0900
Subject: [PATCH 3/3] Add a new tab completion for EXPLAIN (STATS) on psql (I2)

- When you run "EXPLAIN (<tab>" or "EXPLAIN (S<tab>" on psql,
  "STATS" string is displayed.
---
 src/bin/psql/tab-complete.in.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/bin/psql/tab-complete.in.c b/src/bin/psql/tab-complete.in.c
index 1f2ca946fc5..c51332baa78 100644
--- a/src/bin/psql/tab-complete.in.c
+++ b/src/bin/psql/tab-complete.in.c
@@ -4338,8 +4338,8 @@ match_previous_words(int pattern_id,
 		if (ends_with(prev_wd, '(') || ends_with(prev_wd, ','))
 			COMPLETE_WITH("ANALYZE", "VERBOSE", "COSTS", "SETTINGS", "GENERIC_PLAN",
 						  "BUFFERS", "SERIALIZE", "WAL", "TIMING", "SUMMARY",
-						  "MEMORY", "FORMAT");
-		else if (TailMatches("ANALYZE|VERBOSE|COSTS|SETTINGS|GENERIC_PLAN|BUFFERS|WAL|TIMING|SUMMARY|MEMORY"))
+						  "MEMORY", "FORMAT", "STATS");
+		else if (TailMatches("ANALYZE|VERBOSE|COSTS|SETTINGS|GENERIC_PLAN|BUFFERS|WAL|TIMING|SUMMARY|MEMORY|STATS"))
 			COMPLETE_WITH("ON", "OFF");
 		else if (TailMatches("SERIALIZE"))
 			COMPLETE_WITH("TEXT", "NONE", "BINARY");
-- 
2.39.5