MDEV-443: Galera: Server crashes on flushing tables for SST if started with...

MDEV-443: Galera: Server crashes on flushing tables for SST if started with character_set_server utf16 or utf32 or ucs2, and with wsrep_sst_method=rsync

Analysis: In SST Galera directly calls parser using current client character
set. Similarly in BF Galera uses client character set to apply. However,
there are character sets that are not currently supported by the parser.

Fix: If currenct client character set is one of those that is not supported
by the parser, temporally set character set to latin1 before we enter
parser and restore it after we have parsed.

sql/sql_parse.cc

@@ -892,8 +892,17 @@ bool do_command(THD *thd)
   if (WSREP(thd)) {
     while (thd->wsrep_conflict_state== RETRY_AUTOCOMMIT)
     {
-      return_value= dispatch_command(command, thd, thd->wsrep_retry_query, 
+	    CHARSET_INFO *current_charset = thd->variables.character_set_client;
+            if (!is_supported_parser_charset(current_charset))
+            {
+              /* Do not use non-supported parser character sets */
+              WSREP_WARN("Current client character set is non-supported parser character set: %s", current_charset->csname);
+              thd->variables.character_set_client = &my_charset_latin1;
+              WSREP_WARN("For retry temporally setting character set to : %s", my_charset_latin1.csname);
+            }
+	    return_value= dispatch_command(command, thd, thd->wsrep_retry_query,
 				     thd->wsrep_retry_query_len);
+            thd->variables.character_set_client = current_charset;
     }
   }
   if (thd->wsrep_retry_query && thd->wsrep_conflict_state != REPLAYING)
@@ -8119,6 +8128,7 @@ static enum wsrep_status wsrep_apply_sql(
 {
   int error;
   enum wsrep_status ret_code= WSREP_OK;
+  CHARSET_INFO *current_charset = thd->variables.character_set_client;
 
   DBUG_ENTER("wsrep_bf_execute_cb");
   thd->wsrep_exec_mode= REPL_RECV;
@@ -8137,11 +8147,22 @@ static enum wsrep_status wsrep_apply_sql(
     thd->wsrep_conflict_state= NO_CONFLICT;
   mysql_mutex_unlock(&thd->LOCK_wsrep_thd);
 
+  if (!is_supported_parser_charset(current_charset))
+  {
+      /* Do not use non-supported parser character sets */
+      WSREP_WARN("Current client character set is non-supported parser character set: %s", current_charset->csname);
+      thd->variables.character_set_client = &my_charset_latin1;
+      WSREP_WARN("For BF SQL apply temporally setting character set to : %s",
+	      my_charset_latin1.csname);
+  }
+
   if ((error= dispatch_command(COM_QUERY, thd, (char*)sql, sql_len))) {
     WSREP_WARN("BF SQL apply failed: %d, %lld",
                thd->wsrep_conflict_state, (long long)thd->wsrep_trx_seqno);
+    thd->variables.character_set_client = current_charset;
     DBUG_RETURN(WSREP_FATAL);
   }
+  thd->variables.character_set_client = current_charset;
 
   mysql_mutex_lock(&thd->LOCK_wsrep_thd);
   if (thd->wsrep_conflict_state!= NO_CONFLICT && 

sql/wsrep_sst.cc

@@ -14,6 +14,9 @@
    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */
 
 #include <mysqld.h>
+#include <m_ctype.h>
+#include <my_sys.h>
+#include <strfunc.h>
 #include <sql_class.h>
 #include <set_var.h>
 #include <sql_acl.h>
@@ -742,6 +745,19 @@ static int sst_flush_tables(THD* thd)
 
   int err;
   int not_used;
+  CHARSET_INFO *current_charset;
+
+  current_charset = thd->variables.character_set_client;
+
+  if (!is_supported_parser_charset(current_charset))
+  {
+      /* Do not use non-supported parser character sets */
+      WSREP_WARN("Current client character set is non-supported parser character set: %s", current_charset->csname);
+      thd->variables.character_set_client = &my_charset_latin1;
+      WSREP_WARN("For SST temporally setting character set to : %s",
+	      my_charset_latin1.csname);
+  }
+
   if (run_sql_command(thd, "FLUSH TABLES WITH READ LOCK"))
   {
     WSREP_ERROR("Failed to flush and lock tables");
@@ -754,6 +770,9 @@ static int sst_flush_tables(THD* thd)
                               (TABLE_LIST*) 0, &not_used);
   }
 
+  thd->variables.character_set_client = current_charset;
+
+
   if (err)
   {
     WSREP_ERROR("Failed to flush tables: %d (%s)", err, strerror(err));
@@ -796,6 +815,19 @@ static void sst_disallow_writes (THD* thd, bool yes)
 {
   char query_str[64] = { 0, };
   ssize_t const query_max = sizeof(query_str) - 1;
+  CHARSET_INFO *current_charset;
+
+  current_charset = thd->variables.character_set_client;
+
+  if (!is_supported_parser_charset(current_charset))
+  {
+      /* Do not use non-supported parser character sets */
+      WSREP_WARN("Current client character set is non-supported parser character set: %s", current_charset->csname);
+      thd->variables.character_set_client = &my_charset_latin1;
+      WSREP_WARN("For SST temporally setting character set to : %s",
+	      my_charset_latin1.csname);
+  }
+
   snprintf (query_str, query_max, "SET GLOBAL innodb_disallow_writes=%d",
             yes ? 1 : 0);
 
@@ -803,6 +835,7 @@ static void sst_disallow_writes (THD* thd, bool yes)
   {
     WSREP_ERROR("Failed to disallow InnoDB writes");
   }
+  thd->variables.character_set_client = current_charset;
 }
 
 static void* sst_donor_thread (void* a)