From 7ed5563bbee301bf8217080dc78ea6a3e78e23a8 Mon Sep 17 00:00:00 2001
From: SachinSetiya <sachinsetia1001@gmail.com>
Date: Wed, 26 Oct 2016 14:52:24 +0530
Subject: [PATCH] MDEV-11016 wsrep_node_is_ready() check is too strict  
 Problem:-   The condition that checks for node readiness is too strict as it
 does   not allow SELECTs even if these selects do not access any tables.  
 For example,if we run        SELECT 1;   OR        SELECT
 @@max_allowed_packet;   Solution:-   We need not to report this error when
 all_tables(lex->query_tables)   is NULL:

---
 .../suite/galera/r/galera_var_dirty_reads.result    | 13 +++++++++++++
 .../suite/galera/t/galera_var_dirty_reads.test      |  7 +++++++
 sql/sql_parse.cc                                    |  5 ++++-
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/mysql-test/suite/galera/r/galera_var_dirty_reads.result b/mysql-test/suite/galera/r/galera_var_dirty_reads.result
index 6d703c8cf95..6a2aa1eb5e7 100644
--- a/mysql-test/suite/galera/r/galera_var_dirty_reads.result
+++ b/mysql-test/suite/galera/r/galera_var_dirty_reads.result
@@ -18,6 +18,19 @@ SET @@session.wsrep_dirty_reads=ON;
 SELECT * FROM t1;
 i
 1
+SET @@session.wsrep_dirty_reads=OFF;
+SELECT 2;
+2
+2
+SELECT @@max_allowed_packet;
+@@max_allowed_packet
+4194304
+SELECT 2+2 from DUAL;
+2+2
+4
+SELECT sysdate() from DUAL;
+sysdate()
+2016-10-28 23:13:06
 SELECT * FROM t1;
 i
 1
diff --git a/mysql-test/suite/galera/t/galera_var_dirty_reads.test b/mysql-test/suite/galera/t/galera_var_dirty_reads.test
index dfd8d5ecf29..0c81779ca65 100644
--- a/mysql-test/suite/galera/t/galera_var_dirty_reads.test
+++ b/mysql-test/suite/galera/t/galera_var_dirty_reads.test
@@ -36,6 +36,13 @@ SET @@session.wsrep_dirty_reads=ON;
 
 SELECT * FROM t1;
 
+#Select query which does not access table should be allowed MDEV-11016
+SET @@session.wsrep_dirty_reads=OFF;
+SELECT 2;
+SELECT @@max_allowed_packet;
+SELECT 2+2 from DUAL;
+SELECT sysdate() from DUAL;
+
 --disable_query_log
 --eval SET @@global.wsrep_cluster_address = '$wsrep_cluster_address_saved'
 --enable_query_log
diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index a15f3da8e12..41c57dca2ef 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -2650,12 +2650,15 @@ mysql_execute_command(THD *thd)
 
     /*
       Bail out if DB snapshot has not been installed. We however, allow SET,
-      SHOW and SELECT queries (only if wsrep_dirty_reads is set).
+      SHOW and SELECT queries (only if wsrep_dirty_reads is set or when it
+      does not access any table).
     */
     if (lex->sql_command != SQLCOM_SET_OPTION  &&
         !wsrep_is_show_query(lex->sql_command) &&
         !(thd->variables.wsrep_dirty_reads     &&
           lex->sql_command == SQLCOM_SELECT)   &&
+        !(lex->sql_command == SQLCOM_SELECT    &&
+          !all_tables)                         &&
         !wsrep_node_is_ready(thd))
       goto error;
   }