From a6b4ddc2777e29170f6caef41ec25a75899d14d3 Mon Sep 17 00:00:00 2001
From: Tomas Vondra <tomas@2ndquadrant.com>
Date: Thu, 12 Nov 2020 00:39:17 +0100
Subject: [PATCH 1/4] Improve estimation of OR clauses using extended
 statistics

Until now, OR clauses were estimated using extended statistics only when
the whole clause (all the arguments) are compatible. If even just one
argument was found to be incompatible, the whole clause was estimated
ignoring extended statistics. Estimation errors for OR clauses tend to
be fairly mild, so this was considered acceptable, but it may become an
issue for OR clauses with more complex arguments, etc.

This commit relaxes the restriction, using mostly the same logic as AND
clauses. We first apply extended statistics to as many arguments as
possible, and then use the (s1 + s2 - s1 * s2) formula to factor in the
remaining clauses.

The OR clause is still considered incompatible, though. If any argument
is unsupported or references variable not covered by the statistics, the
whole OR clause is incompatible. The consequence is that e.g. clauses

    (a = 1) AND (b = 1 OR c = 1 OR d = 1)

can't be estimated by statistics on (a,b,c) because the OR clause also
references "d". So we'll estimate each of the AND arguments separately,
and the extended statistics will be used only to estimate the OR clause.
This may be solved by creating statistics including the "d" column, but
the issue applies to cases where the clause type is unsupported, e.g.

    (a = 1) AND (b = 1 OR c = 1 OR mod(d,10) = 0)

which can't be solved by adding "d" to the statistics, at least for now.

Author: Tomas Vondra
Reviewed-by: Dean Rasheed, Thomas Munro
Discussion: Discussion: https://www.postgresql.org/message-id/flat/20200113230008.g67iyk4cs3xbnjju@development
---
 src/backend/optimizer/path/clausesel.c        | 141 +++++++++++++--
 src/backend/statistics/extended_stats.c       |  34 +++-
 src/backend/statistics/mcv.c                  |   5 +-
 src/include/optimizer/optimizer.h             |   7 +
 .../statistics/extended_stats_internal.h      |   3 +-
 src/include/statistics/statistics.h           |   3 +-
 src/test/regress/expected/stats_ext.out       | 165 +++++++++++++++++-
 src/test/regress/sql/stats_ext.sql            |  77 +++++++-
 8 files changed, 394 insertions(+), 41 deletions(-)

diff --git a/src/backend/optimizer/path/clausesel.c b/src/backend/optimizer/path/clausesel.c
index 37a735b06b..bbe9591aff 100644
--- a/src/backend/optimizer/path/clausesel.c
+++ b/src/backend/optimizer/path/clausesel.c
@@ -92,7 +92,7 @@ clauselist_selectivity(PlannerInfo *root,
 		 */
 		s1 *= statext_clauselist_selectivity(root, clauses, varRelid,
 											 jointype, sjinfo, rel,
-											 &estimatedclauses);
+											 &estimatedclauses, false);
 	}
 
 	/*
@@ -104,6 +104,62 @@ clauselist_selectivity(PlannerInfo *root,
 											  estimatedclauses);
 }
 
+/*
+ * clauselist_selectivity_or -
+ *	  Compute the selectivity of an implicitly-ORed list of boolean
+ *	  expression clauses.  The list can be empty, in which case 0.0
+ *	  must be returned.  List elements may be either RestrictInfos
+ *	  or bare expression clauses --- the former is preferred since
+ *	  it allows caching of results.
+ *
+ * See clause_selectivity() for the meaning of the additional parameters.
+ *
+ * The basic approach is to apply extended statistics first, on as many
+ * clauses as possible, in order to capture cross-column dependencies etc.
+ * The remaining clauses are then estimated using regular statistics tracked
+ * for individual columns.  This is done by simply passing the clauses to
+ * clauselist_selectivity and then combining the selectivities using the
+ * regular formula (s1+s2 - s1*s2).
+ */
+static Selectivity
+clauselist_selectivity_or(PlannerInfo *root,
+						  List *clauses,
+						  int varRelid,
+						  JoinType jointype,
+						  SpecialJoinInfo *sjinfo)
+{
+	Selectivity	s = 0.0;
+	RelOptInfo *rel;
+	Bitmapset  *estimatedclauses = NULL;
+
+	/*
+	 * Determine if these clauses reference a single relation.  If so, and if
+	 * it has extended statistics, try to apply those.
+	 */
+	rel = find_single_rel_for_clauses(root, clauses);
+	if (rel && rel->rtekind == RTE_RELATION && rel->statlist != NIL)
+	{
+		/*
+		 * Estimate as many clauses as possible using extended statistics.
+		 *
+		 * 'estimatedclauses' tracks the 0-based list position index of
+		 * clauses that we've estimated using extended statistics, and that
+		 * should be ignored.
+		 *
+		 * XXX We can't multiply with current value, because for OR clauses
+		 * we start with 0.0, so we simply assign to 's' directly.
+		 */
+		s = statext_clauselist_selectivity(root, clauses, varRelid,
+										   jointype, sjinfo, rel,
+										   &estimatedclauses, true);
+	}
+
+	/* Estimate the rest of the clauses as if they were independent. */
+	return clauselist_selectivity_simple_or(root, clauses, varRelid,
+											jointype, sjinfo,
+											estimatedclauses, s);
+}
+
 /*
  * clauselist_selectivity_simple -
  *	  Compute the selectivity of an implicitly-ANDed list of boolean
@@ -350,6 +406,65 @@ clauselist_selectivity_simple(PlannerInfo *root,
 	return s1;
 }
 
+/*
+ * clauselist_selectivity_simple_or -
+ *	  Compute the selectivity of an implicitly-ORed list of boolean
+ *	  expression clauses.  The list can be empty, in which case the
+ *	  value passed in the last parameter must be returned.
+ *	  The estimatedclauses bitmap tracks clauses that have already
+ *	  been estimated by other means.
+ *
+ * See clause_selectivity() for the meaning of the additional parameters.
+ *
+ * Our basic approach is to combine selectivities of the subclauses
+ * using the formula (s1 + s2 - s1 * s2).  It's possible some of the
+ * clauses are already estimated by other means, in which case we treat
+ * them as a single logical clause, with the selecitivity passed in the
+ * last parameter.
+ */
+Selectivity
+clauselist_selectivity_simple_or(PlannerInfo *root,
+								 List *clauses,
+								 int varRelid,
+								 JoinType jointype,
+								 SpecialJoinInfo *sjinfo,
+								 Bitmapset *estimatedclauses,
+								 Selectivity s)
+{
+	ListCell   *lc;
+	int			listidx;
+
+	/*
+	 * Selectivities of the remaining clauses for an OR clause are computed
+	 * as s1+s2 - s1*s2 to account for the probable overlap of selected tuple
+	 * sets. The clauses estimated using extended statistics are effectively
+	 * treated as a single clause.
+	 *
+	 * XXX is this too conservative?
+	 */
+	listidx = -1;
+	foreach(lc, clauses)
+	{
+		Selectivity s2;
+
+		listidx++;
+
+		/* skip already estimated clauses */
+		if (bms_is_member(listidx, estimatedclauses))
+			continue;
+
+		s2 = clause_selectivity(root,
+								(Node *) lfirst(lc),
+								varRelid,
+								jointype,
+								sjinfo);
+
+		s = s + s2 - s * s2;
+	}
+
+	return s;
+}
+
 /*
  * addRangeClause --- add a new range clause for clauselist_selectivity
  *
@@ -734,24 +849,14 @@ clause_selectivity(PlannerInfo *root,
 	else if (is_orclause(clause))
 	{
 		/*
-		 * Selectivities for an OR clause are computed as s1+s2 - s1*s2 to
-		 * account for the probable overlap of selected tuple sets.
-		 *
-		 * XXX is this too conservative?
+		 * Almost the same thing as clauselist_selectivity, but with the
+		 * clauses connected by OR.
 		 */
-		ListCell   *arg;
-
-		s1 = 0.0;
-		foreach(arg, ((BoolExpr *) clause)->args)
-		{
-			Selectivity s2 = clause_selectivity(root,
-												(Node *) lfirst(arg),
-												varRelid,
-												jointype,
-												sjinfo);
-
-			s1 = s1 + s2 - s1 * s2;
-		}
+		s1 = clauselist_selectivity_or(root,
+									   ((BoolExpr *) clause)->args,
+									   varRelid,
+									   jointype,
+									   sjinfo);
 	}
 	else if (is_opclause(clause) || IsA(clause, DistinctExpr))
 	{
diff --git a/src/backend/statistics/extended_stats.c b/src/backend/statistics/extended_stats.c
index 36326927c6..f5493bcad6 100644
--- a/src/backend/statistics/extended_stats.c
+++ b/src/backend/statistics/extended_stats.c
@@ -1282,16 +1282,17 @@ statext_is_compatible_clause(PlannerInfo *root, Node *clause, Index relid,
 static Selectivity
 statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varRelid,
 								   JoinType jointype, SpecialJoinInfo *sjinfo,
-								   RelOptInfo *rel, Bitmapset **estimatedclauses)
+								   RelOptInfo *rel, Bitmapset **estimatedclauses,
+								   bool is_or)
 {
 	ListCell   *l;
 	Bitmapset **list_attnums;
 	int			listidx;
-	Selectivity sel = 1.0;
+	Selectivity sel = (is_or) ? 0.0 : 1.0;
 
 	/* check if there's any stats that might be useful for us. */
 	if (!has_stats_of_kind(rel->statlist, STATS_EXT_MCV))
-		return 1.0;
+		return sel;
 
 	list_attnums = (Bitmapset **) palloc(sizeof(Bitmapset *) *
 										 list_length(clauses));
@@ -1377,8 +1378,12 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 		 * columns/clauses. We'll then use the various selectivities computed
 		 * from MCV list to improve it.
 		 */
-		simple_sel = clauselist_selectivity_simple(root, stat_clauses, varRelid,
-												   jointype, sjinfo, NULL);
+		if (is_or)
+			simple_sel = clauselist_selectivity_simple_or(root, stat_clauses, varRelid,
+														  jointype, sjinfo, NULL, 0.0);
+		else
+			simple_sel = clauselist_selectivity_simple(root, stat_clauses, varRelid,
+													   jointype, sjinfo, NULL);
 
 		/*
 		 * Now compute the multi-column estimate from the MCV list, along with
@@ -1386,7 +1391,7 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 		 */
 		mcv_sel = mcv_clauselist_selectivity(root, stat, stat_clauses, varRelid,
 											 jointype, sjinfo, rel,
-											 &mcv_basesel, &mcv_totalsel);
+											 &mcv_basesel, &mcv_totalsel, is_or);
 
 		/* Estimated selectivity of values not covered by MCV matches */
 		other_sel = simple_sel - mcv_basesel;
@@ -1404,7 +1409,10 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 		CLAMP_PROBABILITY(stat_sel);
 
 		/* Factor the estimate from this MCV to the overall estimate. */
-		sel *= stat_sel;
+		if (is_or)
+			sel = sel + stat_sel - sel * stat_sel;
+		else
+			sel *= stat_sel;
 	}
 
 	return sel;
@@ -1417,13 +1425,21 @@ statext_mcv_clauselist_selectivity(PlannerInfo *root, List *clauses, int varReli
 Selectivity
 statext_clauselist_selectivity(PlannerInfo *root, List *clauses, int varRelid,
 							   JoinType jointype, SpecialJoinInfo *sjinfo,
-							   RelOptInfo *rel, Bitmapset **estimatedclauses)
+							   RelOptInfo *rel, Bitmapset **estimatedclauses,
+							   bool is_or)
 {
 	Selectivity sel;
 
 	/* First, try estimating clauses using a multivariate MCV list. */
 	sel = statext_mcv_clauselist_selectivity(root, clauses, varRelid, jointype,
-											 sjinfo, rel, estimatedclauses);
+											 sjinfo, rel, estimatedclauses, is_or);
+
+	/*
+	 * Functional dependencies only work for clauses connected by AND, so for
+	 * OR clauses we're done.
+	 */
+	if (is_or)
+		return sel;
 
 	/*
 	 * Then, apply functional dependencies on the remaining clauses by calling
diff --git a/src/backend/statistics/mcv.c b/src/backend/statistics/mcv.c
index 6a262f1543..7c5841ed37 100644
--- a/src/backend/statistics/mcv.c
+++ b/src/backend/statistics/mcv.c
@@ -1904,7 +1904,8 @@ mcv_clauselist_selectivity(PlannerInfo *root, StatisticExtInfo *stat,
 						   List *clauses, int varRelid,
 						   JoinType jointype, SpecialJoinInfo *sjinfo,
 						   RelOptInfo *rel,
-						   Selectivity *basesel, Selectivity *totalsel)
+						   Selectivity *basesel, Selectivity *totalsel,
+						   bool is_or)
 {
 	int			i;
 	MCVList    *mcv;
@@ -1917,7 +1918,7 @@ mcv_clauselist_selectivity(PlannerInfo *root, StatisticExtInfo *stat,
 	mcv = statext_mcv_load(stat->statOid);
 
 	/* build a match bitmap for the clauses */
-	matches = mcv_get_match_bitmap(root, clauses, stat->keys, mcv, false);
+	matches = mcv_get_match_bitmap(root, clauses, stat->keys, mcv, is_or);
 
 	/* sum frequencies for all the matching MCV items */
 	*basesel = 0.0;
diff --git a/src/include/optimizer/optimizer.h b/src/include/optimizer/optimizer.h
index 3e4171056e..de24d7e1d4 100644
--- a/src/include/optimizer/optimizer.h
+++ b/src/include/optimizer/optimizer.h
@@ -64,6 +64,13 @@ extern Selectivity clauselist_selectivity_simple(PlannerInfo *root,
 												 JoinType jointype,
 												 SpecialJoinInfo *sjinfo,
 												 Bitmapset *estimatedclauses);
+extern Selectivity clauselist_selectivity_simple_or(PlannerInfo *root,
+													List *clauses,
+													int varRelid,
+													JoinType jointype,
+													SpecialJoinInfo *sjinfo,
+													Bitmapset *estimatedclauses,
+													Selectivity s);
 extern Selectivity clauselist_selectivity(PlannerInfo *root,
 										  List *clauses,
 										  int varRelid,
diff --git a/src/include/statistics/extended_stats_internal.h b/src/include/statistics/extended_stats_internal.h
index 61e69696cf..08d639e66a 100644
--- a/src/include/statistics/extended_stats_internal.h
+++ b/src/include/statistics/extended_stats_internal.h
@@ -107,6 +107,7 @@ extern Selectivity mcv_clauselist_selectivity(PlannerInfo *root,
 											  SpecialJoinInfo *sjinfo,
 											  RelOptInfo *rel,
 											  Selectivity *basesel,
-											  Selectivity *totalsel);
+											  Selectivity *totalsel,
+											  bool is_or);
 
 #endif							/* EXTENDED_STATS_INTERNAL_H */
diff --git a/src/include/statistics/statistics.h b/src/include/statistics/statistics.h
index 50fce4935f..c9ed21155c 100644
--- a/src/include/statistics/statistics.h
+++ b/src/include/statistics/statistics.h
@@ -116,7 +116,8 @@ extern Selectivity statext_clauselist_selectivity(PlannerInfo *root,
 												  JoinType jointype,
 												  SpecialJoinInfo *sjinfo,
 												  RelOptInfo *rel,
-												  Bitmapset **estimatedclauses);
+												  Bitmapset **estimatedclauses,
+												  bool is_or);
 extern bool has_stats_of_kind(List *stats, char requiredkind);
 extern StatisticExtInfo *choose_best_statistics(List *stats, char requiredkind,
 												Bitmapset **clause_attnums,
diff --git a/src/test/regress/expected/stats_ext.out b/src/test/regress/expected/stats_ext.out
index 4c3edd213f..0577631ac4 100644
--- a/src/test/regress/expected/stats_ext.out
+++ b/src/test/regress/expected/stats_ext.out
@@ -1113,6 +1113,12 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a = 1 OR b = '
        200 |    200
 (1 row)
 
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a = 1 OR b = ''1'' OR c = 1 OR d IS NOT NULL');
+ estimated | actual 
+-----------+--------
+       200 |    200
+(1 row)
+
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a IN (1, 2, 51, 52) AND b IN ( ''1'', ''2'')');
  estimated | actual 
 -----------+--------
@@ -1173,13 +1179,6 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a < ALL (ARRAY
        100 |    100
 (1 row)
 
--- we can't use the statistic for OR clauses that are not fully covered (missing 'd' attribute)
-SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a = 1 OR b = ''1'' OR c = 1 OR d IS NOT NULL');
- estimated | actual 
------------+--------
-       343 |    200
-(1 row)
-
 -- check change of unrelated column type does not reset the MCV statistics
 ALTER TABLE mcv_lists ALTER COLUMN d TYPE VARCHAR(64);
 SELECT d.stxdmcv IS NOT NULL
@@ -1477,6 +1476,110 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_bool WHERE NOT a AND
          1 |      0
 (1 row)
 
+-- mcv covering just a small fraction of data
+CREATE TABLE mcv_lists_partial (
+    a INT,
+    b INT,
+    c INT
+);
+-- 10 frequent groups, each with 100 elements
+INSERT INTO mcv_lists_partial (a, b, c)
+     SELECT
+         mod(i,10),
+         mod(i,10),
+         mod(i,10)
+     FROM generate_series(0,999) s(i);
+-- 100 groups that will make it to the MCV list (includes the 10 frequent ones)
+INSERT INTO mcv_lists_partial (a, b, c)
+     SELECT
+         i,
+         i,
+         i
+     FROM generate_series(0,99) s(i);
+-- 4000 groups in total, most of which won't make it (just a single item)
+INSERT INTO mcv_lists_partial (a, b, c)
+     SELECT
+         i,
+         i,
+         i
+     FROM generate_series(0,3999) s(i);
+ANALYZE mcv_lists_partial;
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 0');
+ estimated | actual 
+-----------+--------
+         1 |    102
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 0');
+ estimated | actual 
+-----------+--------
+       300 |    102
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 AND b = 10 AND c = 10');
+ estimated | actual 
+-----------+--------
+         1 |      2
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 OR b = 10 OR c = 10');
+ estimated | actual 
+-----------+--------
+         6 |      2
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 10');
+ estimated | actual 
+-----------+--------
+         1 |      0
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 10');
+ estimated | actual 
+-----------+--------
+       204 |    104
+(1 row)
+
+CREATE STATISTICS mcv_lists_partial_stats (mcv) ON a, b, c
+  FROM mcv_lists_partial;
+ANALYZE mcv_lists_partial;
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 0');
+ estimated | actual 
+-----------+--------
+       102 |    102
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 0');
+ estimated | actual 
+-----------+--------
+       504 |    102
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 AND b = 10 AND c = 10');
+ estimated | actual 
+-----------+--------
+         2 |      2
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 OR b = 10 OR c = 10');
+ estimated | actual 
+-----------+--------
+        10 |      2
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 10');
+ estimated | actual 
+-----------+--------
+         1 |      0
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 10');
+ estimated | actual 
+-----------+--------
+       412 |    104
+(1 row)
+
+DROP TABLE mcv_lists_partial;
 -- check the ability to use multiple MCV lists
 CREATE TABLE mcv_lists_multi (
 	a INTEGER,
@@ -1506,12 +1609,36 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE c = 0 AN
        102 |    714
 (1 row)
 
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 AND c = 0');
+ estimated | actual 
+-----------+--------
+       143 |    142
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 OR c = 0');
+ estimated | actual 
+-----------+--------
+      1571 |   1572
+(1 row)
+
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
  estimated | actual 
 -----------+--------
          4 |    142
 (1 row)
 
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE (a = 0 AND b = 0) OR (c = 0 AND d = 0)');
+ estimated | actual 
+-----------+--------
+       298 |   1572
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 OR b = 0 OR c = 0 OR d = 0');
+ estimated | actual 
+-----------+--------
+      2649 |   1572
+(1 row)
+
 -- create separate MCV statistics
 CREATE STATISTICS mcv_lists_multi_1 (mcv) ON a, b FROM mcv_lists_multi;
 CREATE STATISTICS mcv_lists_multi_2 (mcv) ON c, d FROM mcv_lists_multi;
@@ -1528,12 +1655,36 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE c = 0 AN
        714 |    714
 (1 row)
 
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 AND c = 0');
+ estimated | actual 
+-----------+--------
+       143 |    142
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 OR c = 0');
+ estimated | actual 
+-----------+--------
+      1571 |   1572
+(1 row)
+
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
  estimated | actual 
 -----------+--------
        143 |    142
 (1 row)
 
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE (a = 0 AND b = 0) OR (c = 0 AND d = 0)');
+ estimated | actual 
+-----------+--------
+      1571 |   1572
+(1 row)
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 OR b = 0 OR c = 0 OR d = 0');
+ estimated | actual 
+-----------+--------
+      1571 |   1572
+(1 row)
+
 DROP TABLE mcv_lists_multi;
 -- Permission tests. Users should not be able to see specific data values in
 -- the extended statistics, if they lack permission to see those values in
diff --git a/src/test/regress/sql/stats_ext.sql b/src/test/regress/sql/stats_ext.sql
index 9781e590a3..3ec6dda094 100644
--- a/src/test/regress/sql/stats_ext.sql
+++ b/src/test/regress/sql/stats_ext.sql
@@ -561,6 +561,8 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE 4 >= a AND ''0
 
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a = 1 OR b = ''1'' OR c = 1');
 
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a = 1 OR b = ''1'' OR c = 1 OR d IS NOT NULL');
+
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a IN (1, 2, 51, 52) AND b IN ( ''1'', ''2'')');
 
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a IN (1, 2, 51, 52, NULL) AND b IN ( ''1'', ''2'', NULL)');
@@ -581,9 +583,6 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a < ALL (ARRAY
 
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a < ALL (ARRAY[4, 5]) AND b IN (''1'', ''2'', NULL, ''3'') AND c > ANY (ARRAY[1, 2, NULL, 3])');
 
--- we can't use the statistic for OR clauses that are not fully covered (missing 'd' attribute)
-SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists WHERE a = 1 OR b = ''1'' OR c = 1 OR d IS NOT NULL');
-
 -- check change of unrelated column type does not reset the MCV statistics
 ALTER TABLE mcv_lists ALTER COLUMN d TYPE VARCHAR(64);
 
@@ -777,6 +776,70 @@ SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_bool WHERE NOT a AND
 
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_bool WHERE NOT a AND b AND NOT c');
 
+-- mcv covering just a small fraction of data
+CREATE TABLE mcv_lists_partial (
+    a INT,
+    b INT,
+    c INT
+);
+
+-- 10 frequent groups, each with 100 elements
+INSERT INTO mcv_lists_partial (a, b, c)
+     SELECT
+         mod(i,10),
+         mod(i,10),
+         mod(i,10)
+     FROM generate_series(0,999) s(i);
+
+-- 100 groups that will make it to the MCV list (includes the 10 frequent ones)
+INSERT INTO mcv_lists_partial (a, b, c)
+     SELECT
+         i,
+         i,
+         i
+     FROM generate_series(0,99) s(i);
+
+-- 4000 groups in total, most of which won't make it (just a single item)
+INSERT INTO mcv_lists_partial (a, b, c)
+     SELECT
+         i,
+         i,
+         i
+     FROM generate_series(0,3999) s(i);
+
+ANALYZE mcv_lists_partial;
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 0');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 0');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 AND b = 10 AND c = 10');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 OR b = 10 OR c = 10');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 10');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 10');
+
+CREATE STATISTICS mcv_lists_partial_stats (mcv) ON a, b, c
+  FROM mcv_lists_partial;
+
+ANALYZE mcv_lists_partial;
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 0');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 0');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 AND b = 10 AND c = 10');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 10 OR b = 10 OR c = 10');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 AND b = 0 AND c = 10');
+
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_partial WHERE a = 0 OR b = 0 OR c = 10');
+
+DROP TABLE mcv_lists_partial;
+
 -- check the ability to use multiple MCV lists
 CREATE TABLE mcv_lists_multi (
 	a INTEGER,
@@ -799,7 +862,11 @@ ANALYZE mcv_lists_multi;
 -- estimates without any mcv statistics
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 AND b = 0');
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE c = 0 AND d = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 AND c = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 OR c = 0');
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE (a = 0 AND b = 0) OR (c = 0 AND d = 0)');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 OR b = 0 OR c = 0 OR d = 0');
 
 -- create separate MCV statistics
 CREATE STATISTICS mcv_lists_multi_1 (mcv) ON a, b FROM mcv_lists_multi;
@@ -809,7 +876,11 @@ ANALYZE mcv_lists_multi;
 
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 AND b = 0');
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE c = 0 AND d = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 AND c = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE b = 0 OR c = 0');
 SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 AND b = 0 AND c = 0 AND d = 0');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE (a = 0 AND b = 0) OR (c = 0 AND d = 0)');
+SELECT * FROM check_estimated_rows('SELECT * FROM mcv_lists_multi WHERE a = 0 OR b = 0 OR c = 0 OR d = 0');
 
 DROP TABLE mcv_lists_multi;
 
-- 
2.26.2

