Fix bug introduced into mergejoin logic by performance improvement patch of

2005-05-13.  When we find that a new inner tuple can't possibly match any
outer tuple (because it contains a NULL), we can't immediately skip the
tuple when we are in NEXTINNER state.  Doing so can lead to emitting
multiple copies of the tuple in FillInner mode, because we may rescan the
tuple after returning to a previous marked tuple.  Instead, proceed to
NEXTOUTER state the same as we used to do.  After we've found that there's
no need to return to the marked position, we can go to SKIPINNER_ADVANCE
state instead of SKIP_TEST when the inner tuple is unmatchable; this
preserves the performance improvement.  Per bug report from Bruce.
I also made a couple of cosmetic code rearrangements and added a regression
test for the problem.

3 files changed, 77 insertions, 0 deletions

diff --git a/src/test/regress/expected/join.out b/src/test/regress/expected/join.out
index 614f6f07858..8835dac6319 100644
--- a/src/test/regress/expected/join.out
+++ b/src/test/regress/expected/join.out
@@ -2184,3 +2184,31 @@ SELECT * FROM t3;
 ---+---
 (0 rows)
 
+--
+-- regression test for 8.1 merge right join bug
+--
+CREATE TEMP TABLE tt1 ( tt1_id int4, joincol int4 );
+INSERT INTO tt1 VALUES (1, 11);
+INSERT INTO tt1 VALUES (2, NULL);
+CREATE TEMP TABLE tt2 ( tt2_id int4, joincol int4 );
+INSERT INTO tt2 VALUES (21, 11);
+INSERT INTO tt2 VALUES (22, 11);
+set enable_hashjoin to off;
+set enable_nestloop to off;
+-- these should give the same results
+select tt1.*, tt2.* from tt1 left join tt2 on tt1.joincol = tt2.joincol;
+ tt1_id | joincol | tt2_id | joincol 
+--------+---------+--------+---------
+      1 |      11 |     21 |      11
+      1 |      11 |     22 |      11
+      2 |         |        |        
+(3 rows)
+
+select tt1.*, tt2.* from tt2 right join tt1 on tt1.joincol = tt2.joincol;
+ tt1_id | joincol | tt2_id | joincol 
+--------+---------+--------+---------
+      1 |      11 |     21 |      11
+      1 |      11 |     22 |      11
+      2 |         |        |        
+(3 rows)
+
diff --git a/src/test/regress/expected/join_1.out b/src/test/regress/expected/join_1.out
index 725cbee2677..51e14a7d6ab 100644
--- a/src/test/regress/expected/join_1.out
+++ b/src/test/regress/expected/join_1.out
@@ -2184,3 +2184,31 @@ SELECT * FROM t3;
 ---+---
 (0 rows)
 
+--
+-- regression test for 8.1 merge right join bug
+--
+CREATE TEMP TABLE tt1 ( tt1_id int4, joincol int4 );
+INSERT INTO tt1 VALUES (1, 11);
+INSERT INTO tt1 VALUES (2, NULL);
+CREATE TEMP TABLE tt2 ( tt2_id int4, joincol int4 );
+INSERT INTO tt2 VALUES (21, 11);
+INSERT INTO tt2 VALUES (22, 11);
+set enable_hashjoin to off;
+set enable_nestloop to off;
+-- these should give the same results
+select tt1.*, tt2.* from tt1 left join tt2 on tt1.joincol = tt2.joincol;
+ tt1_id | joincol | tt2_id | joincol 
+--------+---------+--------+---------
+      1 |      11 |     21 |      11
+      1 |      11 |     22 |      11
+      2 |         |        |        
+(3 rows)
+
+select tt1.*, tt2.* from tt2 right join tt1 on tt1.joincol = tt2.joincol;
+ tt1_id | joincol | tt2_id | joincol 
+--------+---------+--------+---------
+      1 |      11 |     21 |      11
+      1 |      11 |     22 |      11
+      2 |         |        |        
+(3 rows)
+
diff --git a/src/test/regress/sql/join.sql b/src/test/regress/sql/join.sql
index a5e521e714a..7ef4e46318a 100644
--- a/src/test/regress/sql/join.sql
+++ b/src/test/regress/sql/join.sql
@@ -373,3 +373,24 @@ DELETE FROM t3 USING t1 JOIN t2 USING (a) WHERE t3.x > t1.a;
 SELECT * FROM t3;
 DELETE FROM t3 USING t3 t3_other WHERE t3.x = t3_other.x AND t3.y = t3_other.y;
 SELECT * FROM t3;
+
+--
+-- regression test for 8.1 merge right join bug
+--
+
+CREATE TEMP TABLE tt1 ( tt1_id int4, joincol int4 );
+INSERT INTO tt1 VALUES (1, 11);
+INSERT INTO tt1 VALUES (2, NULL);
+
+CREATE TEMP TABLE tt2 ( tt2_id int4, joincol int4 );
+INSERT INTO tt2 VALUES (21, 11);
+INSERT INTO tt2 VALUES (22, 11);
+
+set enable_hashjoin to off;
+set enable_nestloop to off;
+
+-- these should give the same results
+
+select tt1.*, tt2.* from tt1 left join tt2 on tt1.joincol = tt2.joincol;
+
+select tt1.*, tt2.* from tt2 right join tt1 on tt1.joincol = tt2.joincol;