Fix a bug with SSI and prepared transactions:

If there's a dangerous structure T0 ---> T1 ---> T2, and T2 commits first,
we need to abort something. If T2 commits before both conflicts appear,
then it should be caught by OnConflict_CheckForSerializationFailure. If
both conflicts appear before T2 commits, it should be caught by
PreCommit_CheckForSerializationFailure. But that is actually run when
T2 *prepares*. Fix that in OnConflict_CheckForSerializationFailure, by
treating a prepared T2 as if it committed already.

This is mostly a problem for prepared transactions, which are in prepared
state for some time, but also for regular transactions because they also go
through the prepared state in the SSI code for a short moment when they're
committed.

Kevin Grittner and Dan Ports

3 files changed, 5 insertions, 5 deletions

diff --git a/src/test/regress/expected/prepared_xacts.out b/src/test/regress/expected/prepared_xacts.out
index e094476cb4a..9697ace16a5 100644
--- a/src/test/regress/expected/prepared_xacts.out
+++ b/src/test/regress/expected/prepared_xacts.out
@@ -131,12 +131,12 @@ SELECT * FROM pxtest1;
  ddd
 (2 rows)
 
-INSERT INTO pxtest1 VALUES ('fff');
 -- This should fail, because the two transactions have a write-skew anomaly
-PREPARE TRANSACTION 'foo5';
+INSERT INTO pxtest1 VALUES ('fff');
 ERROR:  could not serialize access due to read/write dependencies among transactions
-DETAIL:  Canceled on commit attempt with conflict in from prepared pivot.
+DETAIL:  Canceled on identification as a pivot, during write.
 HINT:  The transaction might succeed if retried.
+PREPARE TRANSACTION 'foo5';
 SELECT gid FROM pg_prepared_xacts;
  gid  
 ------
diff --git a/src/test/regress/expected/prepared_xacts_1.out b/src/test/regress/expected/prepared_xacts_1.out
index acd90467328..898f278c11e 100644
--- a/src/test/regress/expected/prepared_xacts_1.out
+++ b/src/test/regress/expected/prepared_xacts_1.out
@@ -134,8 +134,8 @@ SELECT * FROM pxtest1;
  aaa
 (1 row)
 
-INSERT INTO pxtest1 VALUES ('fff');
 -- This should fail, because the two transactions have a write-skew anomaly
+INSERT INTO pxtest1 VALUES ('fff');
 PREPARE TRANSACTION 'foo5';
 ERROR:  prepared transactions are disabled
 HINT:  Set max_prepared_transactions to a nonzero value.
diff --git a/src/test/regress/sql/prepared_xacts.sql b/src/test/regress/sql/prepared_xacts.sql
index e06c9d47c13..7902152775c 100644
--- a/src/test/regress/sql/prepared_xacts.sql
+++ b/src/test/regress/sql/prepared_xacts.sql
@@ -74,9 +74,9 @@ SELECT gid FROM pg_prepared_xacts;
 
 BEGIN TRANSACTION ISOLATION LEVEL SERIALIZABLE;
 SELECT * FROM pxtest1;
-INSERT INTO pxtest1 VALUES ('fff');
 
 -- This should fail, because the two transactions have a write-skew anomaly
+INSERT INTO pxtest1 VALUES ('fff');
 PREPARE TRANSACTION 'foo5';
 
 SELECT gid FROM pg_prepared_xacts;