4 files changed, 36 insertions, 8 deletions
diff --git a/src/backend/optimizer/path/indxpath.c b/src/backend/optimizer/path/indxpath.c
index 91aa3fcc00d..1d899f80ae9 100644
--- a/src/backend/optimizer/path/indxpath.c
+++ b/src/backend/optimizer/path/indxpath.c
@@ -3574,10 +3574,13 @@ relation_has_unique_index_for(PlannerInfo *root, RelOptInfo *rel,
 
 		/*
 		 * If the index is not unique, or not immediately enforced, or if it's
-		 * a partial index that doesn't match the query, it's useless here.
+		 * a partial index, it's useless here.  We're unable to make use of
+		 * predOK partial unique indexes due to the fact that
+		 * check_index_predicates() also makes use of join predicates to
+		 * determine if the partial index is usable. Here we need proofs that
+		 * hold true before any joins are evaluated.
 		 */
-		if (!ind->unique || !ind->immediate ||
-			(ind->indpred != NIL && !ind->predOK))
+		if (!ind->unique || !ind->immediate || ind->indpred != NIL)
 			continue;
 
 		/*
diff --git a/src/backend/optimizer/plan/analyzejoins.c b/src/backend/optimizer/plan/analyzejoins.c
index 857f51c752c..4d42625e1d4 100644
--- a/src/backend/optimizer/plan/analyzejoins.c
+++ b/src/backend/optimizer/plan/analyzejoins.c
@@ -595,9 +595,9 @@ rel_supports_distinctness(PlannerInfo *root, RelOptInfo *rel)
 		/*
 		 * For a plain relation, we only know how to prove uniqueness by
 		 * reference to unique indexes.  Make sure there's at least one
-		 * suitable unique index.  It must be immediately enforced, and if
-		 * it's a partial index, it must match the query.  (Keep these
-		 * conditions in sync with relation_has_unique_index_for!)
+		 * suitable unique index.  It must be immediately enforced, and not a
+		 * partial index. (Keep these conditions in sync with
+		 * relation_has_unique_index_for!)
 		 */
 		ListCell   *lc;
 
@@ -605,8 +605,7 @@ rel_supports_distinctness(PlannerInfo *root, RelOptInfo *rel)
 		{
 			IndexOptInfo *ind = (IndexOptInfo *) lfirst(lc);
 
-			if (ind->unique && ind->immediate &&
-				(ind->indpred == NIL || ind->predOK))
+			if (ind->unique && ind->immediate && ind->indpred == NIL)
 				return true;
 		}
 	}
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 8adaef05fa7..d7153a6fd90 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -6346,6 +6346,23 @@ left join j2 on j1.id1 = j2.id1 where j1.id2 = 1;
          Output: j2.id1, j2.id2
 (8 rows)
 
+create unique index j1_id2_idx on j1(id2) where id2 is not null;
+-- ensure we don't use a partial unique index as unique proofs
+explain (verbose, costs off)
+select * from j1
+inner join j2 on j1.id2 = j2.id2;
+                QUERY PLAN                
+------------------------------------------
+ Nested Loop
+   Output: j1.id1, j1.id2, j2.id1, j2.id2
+   Join Filter: (j1.id2 = j2.id2)
+   ->  Seq Scan on public.j2
+         Output: j2.id1, j2.id2
+   ->  Seq Scan on public.j1
+         Output: j1.id1, j1.id2
+(7 rows)
+
+drop index j1_id2_idx;
 -- validate logic in merge joins which skips mark and restore.
 -- it should only do this if all quals which were used to detect the unique
 -- are present as join quals, and not plain quals.
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 89e58bed7d7..92ae4ca79c7 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -2204,6 +2204,15 @@ explain (verbose, costs off)
 select * from j1
 left join j2 on j1.id1 = j2.id1 where j1.id2 = 1;
 
+create unique index j1_id2_idx on j1(id2) where id2 is not null;
+
+-- ensure we don't use a partial unique index as unique proofs
+explain (verbose, costs off)
+select * from j1
+inner join j2 on j1.id2 = j2.id2;
+
+drop index j1_id2_idx;
+
 -- validate logic in merge joins which skips mark and restore.
 -- it should only do this if all quals which were used to detect the unique
 -- are present as join quals, and not plain quals.