From bccbd5c493a5350a7dd36e0349f2ad6d05863e89 Mon Sep 17 00:00:00 2001
From: unknown <davi@moksha.local>
Date: Thu, 30 Aug 2007 16:11:53 -0300
Subject: [PATCH 1/2] Bug#28587 SELECT is blocked by INSERT waiting on read
 lock, even with low_priority_updates

The problem is that a SELECT on one thread is blocked by INSERT ... ON
DUPLICATE KEY UPDATE on another thread even when low_priority_updates is
activated.

The solution is to possibly downgrade the lock type to the setting of
low_priority_updates if the INSERT cannot be concurrent.


sql/sql_insert.cc:
  Possibly downgrade lock type to the the setting of low_priority_updates if
  if the INSERT cannot be concurrent.
---
 sql/sql_insert.cc | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sql/sql_insert.cc b/sql/sql_insert.cc
index bd21d929291..f07af393070 100644
--- a/sql/sql_insert.cc
+++ b/sql/sql_insert.cc
@@ -417,7 +417,7 @@ void upgrade_lock_type(THD *thd, thr_lock_type *lock_type,
   if (duplic == DUP_UPDATE ||
       duplic == DUP_REPLACE && *lock_type == TL_WRITE_CONCURRENT_INSERT)
   {
-    *lock_type= TL_WRITE;
+    *lock_type= TL_WRITE_DEFAULT;
     return;
   }
 

From 97844e982b8e75752bf145392982a9c8562cd125 Mon Sep 17 00:00:00 2001
From: unknown <davi@moksha.local>
Date: Thu, 30 Aug 2007 16:19:23 -0300
Subject: [PATCH 2/2] Post-merge test case with wait_condition for Bug#28587

mysql-test/r/insert_update.result:
  Post-merge: add test case result for Bug#28587.
mysql-test/t/insert_update.test:
  Post-merge: add test case for Bug#28587.
---
 mysql-test/r/insert_update.result | 19 +++++++++++++++++
 mysql-test/t/insert_update.test   | 35 +++++++++++++++++++++++++++++++
 2 files changed, 54 insertions(+)

diff --git a/mysql-test/r/insert_update.result b/mysql-test/r/insert_update.result
index 704cf444681..3aec9594d36 100644
--- a/mysql-test/r/insert_update.result
+++ b/mysql-test/r/insert_update.result
@@ -407,3 +407,22 @@ select if( @stamp1 = @stamp2, "correct", "wrong");
 if( @stamp1 = @stamp2, "correct", "wrong")
 correct
 drop table t1;
+connection: default
+set low_priority_updates=1;
+drop table if exists t1;
+create table t1 (a int, b int, unique key t1$a (a));
+lock table t1 read;
+connection: update
+set low_priority_updates=1;
+show variables like 'low_priority_updates';
+Variable_name	Value
+low_priority_updates	ON
+insert into t1 values (1, 2) ON DUPLICATE KEY UPDATE b = 2;;
+connection: select
+select * from t1;
+a	b
+connection: default
+select * from t1;
+a	b
+drop table t1;
+set low_priority_updates=default;
diff --git a/mysql-test/t/insert_update.test b/mysql-test/t/insert_update.test
index 67f21731afe..aad241e031f 100644
--- a/mysql-test/t/insert_update.test
+++ b/mysql-test/t/insert_update.test
@@ -306,3 +306,38 @@ insert into t1(f1) values(1) on duplicate key update f1=1;
 select @stamp2:=f2 from t1;
 select if( @stamp1 = @stamp2, "correct", "wrong");
 drop table t1;
+
+#
+# Bug#28587 SELECT is blocked by INSERT waiting on read lock, even with low_priority_updates
+#
+--echo connection: default
+set low_priority_updates=1;
+--disable_warnings
+drop table if exists t1;
+--enable_warnings
+create table t1 (a int, b int, unique key t1$a (a));
+lock table t1 read;
+connect (update,localhost,root,,);
+connection update;
+--echo connection: update
+set low_priority_updates=1;
+show variables like 'low_priority_updates';
+let $ID= `select connection_id()`;
+--send insert into t1 values (1, 2) ON DUPLICATE KEY UPDATE b = 2;
+connection default;
+# we must wait till the insert opens and locks the table
+let $wait_condition=
+  select count(*) = 1 from information_schema.processlist
+  where state = "Locked" and id = $ID;
+--source include/wait_condition.inc
+connect (select,localhost,root,,);
+--echo connection: select
+select * from t1;
+connection default;
+--echo connection: default
+select * from t1;
+connection default;
+disconnect update;
+disconnect select;
+drop table t1;
+set low_priority_updates=default;