Fix EvalPlanQual rechecking during MERGE.

Under some circumstances, concurrent MERGE operations could lead to
inconsistent results, that varied according the plan chosen. This was
caused by a lack of rowmarks on the source relation, which meant that
EvalPlanQual rechecking was not guaranteed to return the same source
tuples when re-running the join query.

Fix by ensuring that preprocess_rowmarks() sets up PlanRowMarks for
all non-target relations used in MERGE, in the same way that it does
for UPDATE and DELETE.

Per bug #18103. Back-patch to v15, where MERGE was introduced.

Dean Rasheed, reviewed by Richard Guo.

Discussion: https://postgr.es/m/18103-c4386baab8e355e3%40postgresql.org

3 files changed, 194 insertions, 0 deletions

diff --git a/src/test/isolation/expected/merge-join.out b/src/test/isolation/expected/merge-join.out
new file mode 100644
index 00000000000..57f048c52e5
--- /dev/null
+++ b/src/test/isolation/expected/merge-join.out
@@ -0,0 +1,148 @@
+Parsed test spec with 2 sessions
+
+starting permutation: b1 m1 s1 c1 b2 m2 s2 c2
+step b1: BEGIN ISOLATION LEVEL READ COMMITTED;
+step m1: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+step s1: SELECT * FROM tgt;
+id|val
+--+---
+ 1| 10
+ 2| 20
+ 3| 30
+(3 rows)
+
+step c1: COMMIT;
+step b2: BEGIN ISOLATION LEVEL READ COMMITTED;
+step m2: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+step s2: SELECT * FROM tgt;
+id|val
+--+---
+ 1| 10
+ 2| 20
+ 3| 30
+(3 rows)
+
+step c2: COMMIT;
+
+starting permutation: b1 b2 m1 hj ex m2 c1 c2 s1
+step b1: BEGIN ISOLATION LEVEL READ COMMITTED;
+step b2: BEGIN ISOLATION LEVEL READ COMMITTED;
+step m1: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+step hj: SET LOCAL enable_mergejoin = off; SET LOCAL enable_nestloop = off;
+step ex: EXPLAIN (verbose, costs off)
+           MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+QUERY PLAN                                         
+---------------------------------------------------
+Merge on public.tgt                                
+  ->  Hash Left Join                               
+        Output: tgt.ctid, src.val, src.id, src.ctid
+        Inner Unique: true                         
+        Hash Cond: (src.id = tgt.id)               
+        ->  Seq Scan on public.src                 
+              Output: src.val, src.id, src.ctid    
+        ->  Hash                                   
+              Output: tgt.ctid, tgt.id             
+              ->  Seq Scan on public.tgt           
+                    Output: tgt.ctid, tgt.id       
+(11 rows)
+
+step m2: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val); <waiting ...>
+step c1: COMMIT;
+step m2: <... completed>
+step c2: COMMIT;
+step s1: SELECT * FROM tgt;
+id|val
+--+---
+ 1| 10
+ 2| 20
+ 3| 30
+(3 rows)
+
+
+starting permutation: b1 b2 m1 mj ex m2 c1 c2 s1
+step b1: BEGIN ISOLATION LEVEL READ COMMITTED;
+step b2: BEGIN ISOLATION LEVEL READ COMMITTED;
+step m1: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+step mj: SET LOCAL enable_hashjoin = off; SET LOCAL enable_nestloop = off;
+step ex: EXPLAIN (verbose, costs off)
+           MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+QUERY PLAN                                         
+---------------------------------------------------
+Merge on public.tgt                                
+  ->  Merge Left Join                              
+        Output: tgt.ctid, src.val, src.id, src.ctid
+        Inner Unique: true                         
+        Merge Cond: (src.id = tgt.id)              
+        ->  Index Scan using src_pkey on public.src
+              Output: src.val, src.id, src.ctid    
+        ->  Index Scan using tgt_pkey on public.tgt
+              Output: tgt.ctid, tgt.id             
+(9 rows)
+
+step m2: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val); <waiting ...>
+step c1: COMMIT;
+step m2: <... completed>
+step c2: COMMIT;
+step s1: SELECT * FROM tgt;
+id|val
+--+---
+ 1| 10
+ 2| 20
+ 3| 30
+(3 rows)
+
+
+starting permutation: b1 b2 m1 nl ex m2 c1 c2 s1
+step b1: BEGIN ISOLATION LEVEL READ COMMITTED;
+step b2: BEGIN ISOLATION LEVEL READ COMMITTED;
+step m1: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+step nl: SET LOCAL enable_hashjoin = off; SET LOCAL enable_mergejoin = off;
+step ex: EXPLAIN (verbose, costs off)
+           MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val);
+QUERY PLAN                                         
+---------------------------------------------------
+Merge on public.tgt                                
+  ->  Nested Loop Left Join                        
+        Output: tgt.ctid, src.val, src.id, src.ctid
+        Inner Unique: true                         
+        ->  Seq Scan on public.src                 
+              Output: src.val, src.id, src.ctid    
+        ->  Index Scan using tgt_pkey on public.tgt
+              Output: tgt.ctid, tgt.id             
+              Index Cond: (tgt.id = src.id)        
+(9 rows)
+
+step m2: MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val); <waiting ...>
+step c1: COMMIT;
+step m2: <... completed>
+step c2: COMMIT;
+step s1: SELECT * FROM tgt;
+id|val
+--+---
+ 1| 10
+ 2| 20
+ 3| 30
+(3 rows)
+
diff --git a/src/test/isolation/isolation_schedule b/src/test/isolation/isolation_schedule
index 4fc56ae99c9..b2be88ead1d 100644
--- a/src/test/isolation/isolation_schedule
+++ b/src/test/isolation/isolation_schedule
@@ -51,6 +51,7 @@ test: merge-insert-update
 test: merge-delete
 test: merge-update
 test: merge-match-recheck
+test: merge-join
 test: delete-abort-savept
 test: delete-abort-savept-2
 test: aborted-keyrevoke
diff --git a/src/test/isolation/specs/merge-join.spec b/src/test/isolation/specs/merge-join.spec
new file mode 100644
index 00000000000..e33a02ccabc
--- /dev/null
+++ b/src/test/isolation/specs/merge-join.spec
@@ -0,0 +1,45 @@
+# MERGE JOIN
+#
+# This test checks the EPQ recheck mechanism during MERGE when joining to a
+# source table using different join methods, per bug #18103
+
+setup
+{
+  CREATE TABLE src (id int PRIMARY KEY, val int);
+  CREATE TABLE tgt (id int PRIMARY KEY, val int);
+  INSERT INTO src SELECT x, x*10 FROM generate_series(1,3) g(x);
+  INSERT INTO tgt SELECT x, x FROM generate_series(1,3) g(x);
+}
+
+teardown
+{
+  DROP TABLE src, tgt;
+}
+
+session s1
+step b1  { BEGIN ISOLATION LEVEL READ COMMITTED; }
+step m1  { MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val); }
+step s1  { SELECT * FROM tgt; }
+step c1  { COMMIT; }
+
+session s2
+step b2  { BEGIN ISOLATION LEVEL READ COMMITTED; }
+step hj  { SET LOCAL enable_mergejoin = off; SET LOCAL enable_nestloop = off; }
+step mj  { SET LOCAL enable_hashjoin = off; SET LOCAL enable_nestloop = off; }
+step nl  { SET LOCAL enable_hashjoin = off; SET LOCAL enable_mergejoin = off; }
+step ex  { EXPLAIN (verbose, costs off)
+           MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val); }
+step m2  { MERGE INTO tgt USING src ON tgt.id = src.id
+             WHEN MATCHED THEN UPDATE SET val = src.val
+             WHEN NOT MATCHED THEN INSERT VALUES (src.id, src.val); }
+step s2  { SELECT * FROM tgt; }
+step c2  { COMMIT; }
+
+permutation b1 m1 s1 c1 b2 m2 s2 c2
+permutation b1 b2 m1 hj ex m2 c1 c2 s1
+permutation b1 b2 m1 mj ex m2 c1 c2 s1
+permutation b1 b2 m1 nl ex m2 c1 c2 s1