MDEV-11479.patch

diff --git a/sql/sql_parse.cc b/sql/sql_parse.cc
index 5169b7c..b214a17 100644
--- a/sql/sql_parse.cc
+++ b/sql/sql_parse.cc
@@ -2649,13 +2649,16 @@ 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).
+      Bail out if DB snapshot has not been installed. SET and SHOW commands,
+      however, are always allowed.
+
+      We additionally allow all other commands that do not change data in
+      case wsrep_dirty_reads is enabled.
     */
     if (lex->sql_command != SQLCOM_SET_OPTION  &&
         !wsrep_is_show_query(lex->sql_command) &&
         !(thd->variables.wsrep_dirty_reads     &&
-          lex->sql_command == SQLCOM_SELECT)   &&
+          !is_update_query(lex->sql_command))  &&
         !wsrep_node_is_ready(thd))
       goto error;
   }
diff --git a/sql/sys_vars.cc b/sql/sys_vars.cc
index 0518e43..bb349e7 100644
--- a/sql/sys_vars.cc
+++ b/sql/sys_vars.cc
@@ -4976,8 +4976,9 @@ static Sys_var_mybool Sys_wsrep_restart_slave(
        GLOBAL_VAR(wsrep_restart_slave), CMD_LINE(OPT_ARG), DEFAULT(FALSE));
 
 static Sys_var_mybool Sys_wsrep_dirty_reads(
-       "wsrep_dirty_reads", "Do not reject SELECT queries even when the node "
-       "is not ready.", SESSION_ONLY(wsrep_dirty_reads), NO_CMD_LINE,
+       "wsrep_dirty_reads",
+       "Allow reads even when the node is not in the primary component.",
+       SESSION_VAR(wsrep_dirty_reads), CMD_LINE(OPT_ARG),
        DEFAULT(FALSE), NO_MUTEX_GUARD, NOT_IN_BINLOG);
 
 static Sys_var_uint Sys_wsrep_gtid_domain_id(
diff --git a/sql/wsrep_mysqld.cc b/sql/wsrep_mysqld.cc
index 0deb19d..62d7b7e 100644
--- a/sql/wsrep_mysqld.cc
+++ b/sql/wsrep_mysqld.cc
@@ -96,6 +96,8 @@ bool wsrep_new_cluster                 = false; // Bootstrap the cluster ?
 bool wsrep_gtid_mode                   = 0;
 // gtid_domain_id for galera transactions.
 uint32 wsrep_gtid_domain_id            = 0;
+// Allow reads even if the node is not in the primary component.
+bool wsrep_dirty_reads                 = false;
 
 /*
  * End configuration options
@@ -958,6 +960,8 @@ bool wsrep_must_sync_wait (THD* thd, uint mask)
 {
   return (thd->variables.wsrep_sync_wait & mask) &&
     thd->variables.wsrep_on &&
+    !(thd->variables.wsrep_dirty_reads &&
+      !is_update_query(thd->lex->sql_command)) &&
     !thd->in_active_multi_stmt_transaction() &&
     thd->wsrep_conflict_state != REPLAYING &&
     thd->wsrep_sync_wait_gtid.seqno == WSREP_SEQNO_UNDEFINED;
diff --git a/sql/wsrep_mysqld.h b/sql/wsrep_mysqld.h
index 04ccc1a..cf549ff 100644
--- a/sql/wsrep_mysqld.h
+++ b/sql/wsrep_mysqld.h
@@ -89,6 +89,7 @@ extern ulong       wsrep_running_threads;
 extern bool        wsrep_new_cluster;
 extern bool        wsrep_gtid_mode;
 extern uint32      wsrep_gtid_domain_id;
+extern bool        wsrep_dirty_reads;
 
 enum enum_wsrep_OSU_method {
     WSREP_OSU_TOI,