Fix FK constraint violation in applier, after ALTER TABLE ADD FK

Adding a FK constraint to an existing table (ALTER TABLE ADD FOREIGN
KEY) causes the applier to fail, if a concurrent DML statement that
violate the new constraint (i.e. a DELETE or UPDATE of record in the
parent table).

For exmaple, the following scenario causes a crash in the applier:

1. ALTER successfully adds FK constraint in node_1
2. On node_2 is UPDATE is in pre_commit() and has certified successfully
3. ALTER is delivered in node_2 and BF aborts DML
4. Applying UPDATE event causes FK violation in node_1

To avoid this situation it is necessary for UPDATE to fail during
certification. And for the UPDATE to fail certfication it is necessary
that ALTER appends certification keys for both the child and the parent
table. Before this patch, ALTER TABLE ADD FK only appended keys for
child table which is ALTERed.

1 files changed, 9 insertions, 8 deletions

diff --git a/sql/sql_alter.cc b/sql/sql_alter.cc
index 0b4636c1f0f..1d69b06d798 100644
--- a/sql/sql_alter.cc
+++ b/sql/sql_alter.cc
@@ -106,14 +106,10 @@ bool Alter_table_statement::execute(THD *thd)
       (!thd->is_current_stmt_binlog_format_row() ||
        !find_temporary_table(thd, first_table)))
   {
-    if (wsrep_to_isolation_begin(thd,
-                                 lex->name.str ? select_lex->db : NULL,
-                                 lex->name.str ? lex->name.str : NULL,
-                                 first_table))
-    {
-      WSREP_WARN("ALTER TABLE isolation failure");
-      DBUG_RETURN(TRUE);
-    }
+    WSREP_TO_ISOLATION_BEGIN_ALTER(((lex->name.str) ? select_lex->db : NULL),
+                                    ((lex->name.str) ? lex->name.str : NULL),
+                                    first_table,
+                                    &alter_info);
 
     thd->variables.auto_increment_offset = 1;
     thd->variables.auto_increment_increment = 1;
@@ -128,6 +124,11 @@ bool Alter_table_statement::execute(THD *thd)
                             lex->ignore, lex->online);
 
 #ifdef WITH_WSREP
+error:
+  {
+    WSREP_WARN("ALTER TABLE isolation failure");
+    DBUG_RETURN(TRUE);
+  }
 #endif /* WITH_WSREP */
   DBUG_RETURN(result);
 }