diff --git a/src/backend/optimizer/path/joinpath.c b/src/backend/optimizer/path/joinpath.c
index 5aedcd1..39e2ddd 100644
*** a/src/backend/optimizer/path/joinpath.c
--- b/src/backend/optimizer/path/joinpath.c
*************** add_paths_to_joinrel(PlannerInfo *root,
*** 126,133 ****
  	 *
  	 * We have some special cases: for JOIN_SEMI and JOIN_ANTI, it doesn't
  	 * matter since the executor can make the equivalent optimization anyway;
! 	 * we need not expend planner cycles on proofs.  For JOIN_UNIQUE_INNER, we
! 	 * know we're going to force uniqueness of the innerrel below.  For
  	 * JOIN_UNIQUE_OUTER, pass JOIN_INNER to avoid letting that value escape
  	 * this module.
  	 */
--- 126,136 ----
  	 *
  	 * We have some special cases: for JOIN_SEMI and JOIN_ANTI, it doesn't
  	 * matter since the executor can make the equivalent optimization anyway;
! 	 * we need not expend planner cycles on proofs.  For JOIN_UNIQUE_INNER, if
! 	 * the LHS covers all of the associated semijoin's min_lefthand, then it's
! 	 * appropriate to set inner_unique because the path produced by
! 	 * create_unique_path will be unique relative to the LHS.  (If we have an
! 	 * LHS that's only part of the min_lefthand, that is *not* true.)  For
  	 * JOIN_UNIQUE_OUTER, pass JOIN_INNER to avoid letting that value escape
  	 * this module.
  	 */
*************** add_paths_to_joinrel(PlannerInfo *root,
*** 138,144 ****
  			extra.inner_unique = false; /* well, unproven */
  			break;
  		case JOIN_UNIQUE_INNER:
! 			extra.inner_unique = true;
  			break;
  		case JOIN_UNIQUE_OUTER:
  			extra.inner_unique = innerrel_is_unique(root, outerrel, innerrel,
--- 141,148 ----
  			extra.inner_unique = false; /* well, unproven */
  			break;
  		case JOIN_UNIQUE_INNER:
! 			extra.inner_unique = bms_is_subset(sjinfo->min_lefthand,
! 											   outerrel->relids);
  			break;
  		case JOIN_UNIQUE_OUTER:
  			extra.inner_unique = innerrel_is_unique(root, outerrel, innerrel,
diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 69ce7aa..87ff365 100644
*** a/src/test/regress/expected/join.out
--- b/src/test/regress/expected/join.out
*************** reset enable_sort;
*** 5634,5636 ****
--- 5634,5665 ----
  drop table j1;
  drop table j2;
  drop table j3;
+ -- check that semijoin inner is not seen as unique for a portion of the outerrel
+ explain (verbose, costs off)
+ select t1.unique1, t2.hundred
+ from onek t1, tenk1 t2
+ where exists (select 1 from tenk1 t3
+               where t3.thousand = t1.unique1 and t3.tenthous = t2.hundred)
+       and t1.unique1 < 1;
+                                    QUERY PLAN                                    
+ ---------------------------------------------------------------------------------
+  Nested Loop
+    Output: t1.unique1, t2.hundred
+    ->  Hash Join
+          Output: t1.unique1, t3.tenthous
+          Hash Cond: (t3.thousand = t1.unique1)
+          ->  HashAggregate
+                Output: t3.thousand, t3.tenthous
+                Group Key: t3.thousand, t3.tenthous
+                ->  Index Only Scan using tenk1_thous_tenthous on public.tenk1 t3
+                      Output: t3.thousand, t3.tenthous
+          ->  Hash
+                Output: t1.unique1
+                ->  Index Only Scan using onek_unique1 on public.onek t1
+                      Output: t1.unique1
+                      Index Cond: (t1.unique1 < 1)
+    ->  Index Only Scan using tenk1_hundred on public.tenk1 t2
+          Output: t2.hundred
+          Index Cond: (t2.hundred = t3.tenthous)
+ (18 rows)
+ 
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index 4fc8fd5..a36e29f 100644
*** a/src/test/regress/sql/join.sql
--- b/src/test/regress/sql/join.sql
*************** reset enable_sort;
*** 1856,1858 ****
--- 1856,1866 ----
  drop table j1;
  drop table j2;
  drop table j3;
+ 
+ -- check that semijoin inner is not seen as unique for a portion of the outerrel
+ explain (verbose, costs off)
+ select t1.unique1, t2.hundred
+ from onek t1, tenk1 t2
+ where exists (select 1 from tenk1 t3
+               where t3.thousand = t1.unique1 and t3.tenthous = t2.hundred)
+       and t1.unique1 < 1;