Invalidate catalog snapshot upon starting a new global session

Also add a test case which demonstrates the problem of using wrong snapshot or
stale command id on datanode-to-datanode connection

3 files changed, 90 insertions, 0 deletions

diff --git a/src/backend/utils/init/miscinit.c b/src/backend/utils/init/miscinit.c
index c3be358f45..f3693f332f 100644
--- a/src/backend/utils/init/miscinit.c
+++ b/src/backend/utils/init/miscinit.c
@@ -559,6 +559,13 @@ retry:
 		MyFirstBackendId = firstBackend;
 	}
 
+	/*
+	 * Also invalidate any catalog snapshot which may become stale since this
+	 * session may join some open transaction which may have done catalog
+	 * changes that are not reflected in the current catalog snapshot
+	 */
+	InvalidateCatalogSnapshot();
+
 	if (reset)
 	{
 		/*
diff --git a/src/test/regress/expected/transactions.out b/src/test/regress/expected/transactions.out
index fbf4a8430f..49d5407517 100644
--- a/src/test/regress/expected/transactions.out
+++ b/src/test/regress/expected/transactions.out
@@ -533,6 +533,48 @@ select * from xacttest order by a, b;
  807 |  324.78
  817 | 777.777
 (5 rows)
+rollback;
+-- test case for relations which are created and accessed in the same
+-- transaction, especially when the queries require datanode-to-datanode
+-- connections. In the past we had failed to use the correct snapshot in such
+-- cases 
+begin;
+create table a_snap (
+     code char not null,
+     constraint a_snap_pk primary key (code)
+);
+create table b_snap (
+     a char not null,
+     num integer not null,
+     constraint b_snap_pk primary key (a, num)
+);
+create table c_snap (
+     name char not null,
+     a char,
+     constraint c_snap_pk primary key (name)
+);
+insert into a_snap (code) values ('p');
+insert into a_snap (code) values ('q');
+insert into b_snap (a, num) values ('p', 1);
+insert into b_snap (a, num) values ('p', 2);
+insert into c_snap (name, a) values ('A', 'p');
+insert into c_snap (name, a) values ('B', 'q');
+insert into c_snap (name, a) values ('C', null);
+select c_snap.name, ss.code, ss.b_cnt, ss.const
+from c_snap left join
+  (select a_snap.code, coalesce(b_grp.cnt, 0) as b_cnt, -1 as const
+   from a_snap left join
+     (select count(1) as cnt, b_snap.a from b_snap group by b_snap.a) as b_grp
+     on a_snap.code = b_grp.a
+  ) as ss
+  on (c_snap.a = ss.code)
+order by c_snap.name;
+ name | code | b_cnt | const 
+------+------+-------+-------
+ A    | p    |     2 |    -1
+ B    | q    |     0 |    -1
+ C    |      |       |      
+(3 rows)
 
 rollback;
 -- test case for problems with dropping an open relation during abort
diff --git a/src/test/regress/sql/transactions.sql b/src/test/regress/sql/transactions.sql
index 7cdf41e283..d99fbf6500 100644
--- a/src/test/regress/sql/transactions.sql
+++ b/src/test/regress/sql/transactions.sql
@@ -315,6 +315,47 @@ update xacttest set a = max_xacttest() + 10 where a > 0;
 select * from xacttest order by a, b;
 rollback;
 
+-- test case for relations which are created and accessed in the same
+-- transaction, especially when the queries require datanode-to-datanode
+-- connections. In the past we had failed to use the correct snapshot in such
+-- cases 
+
+begin;
+
+create table a_snap (
+     code char not null,
+     constraint a_snap_pk primary key (code)
+);
+create table b_snap (
+     a char not null,
+     num integer not null,
+     constraint b_snap_pk primary key (a, num)
+);
+create table c_snap (
+     name char not null,
+     a char,
+     constraint c_snap_pk primary key (name)
+);
+
+insert into a_snap (code) values ('p');
+insert into a_snap (code) values ('q');
+insert into b_snap (a, num) values ('p', 1);
+insert into b_snap (a, num) values ('p', 2);
+insert into c_snap (name, a) values ('A', 'p');
+insert into c_snap (name, a) values ('B', 'q');
+insert into c_snap (name, a) values ('C', null);
+
+select c_snap.name, ss.code, ss.b_cnt, ss.const
+from c_snap left join
+  (select a_snap.code, coalesce(b_grp.cnt, 0) as b_cnt, -1 as const
+   from a_snap left join
+     (select count(1) as cnt, b_snap.a from b_snap group by b_snap.a) as b_grp
+     on a_snap.code = b_grp.a
+  ) as ss
+  on (c_snap.a = ss.code)
+order by c_snap.name;
+
+rollback;
 
 -- test case for problems with dropping an open relation during abort
 BEGIN;