WL#5151: Conversion between different types when replicating

Row-based replication requires the types of columns on the
master and slave to be approximately the same (some safe
conversions between strings are allowed), but does not
allow safe conversions between fields of similar types such
as TINYINT and INT.

This patch implement type conversions between similar fields
on the master and slave.

The conversions are controlled using a new variable
SLAVE_TYPE_CONVERSIONS of type SET('ALL_LOSSY','ALL_NON_LOSSY').

Non-lossy conversions are any conversions that do not run the
risk of losing any information, while lossy conversions can
potentially truncate the value. The column definitions are
checked to decide if the conversion is acceptable.

If neither conversion is enabled, it is required that the
definitions of the columns are identical on master and slave.

Conversion is done by creating an internal conversion table,
unpacking the master data into it, and then copy the data to
the real table on the slave.

1 files changed, 18 insertions, 4 deletions

diff --git a/sql/log_event_old.cc b/sql/log_event_old.cc
index 3389821a718..10d1dcaa27a 100644
--- a/sql/log_event_old.cc
+++ b/sql/log_event_old.cc
@@ -107,14 +107,24 @@ Old_rows_log_event::do_apply_event(Old_rows_log_event *ev, const Relay_log_info
       RPL_TABLE_LIST *ptr= rli->tables_to_lock;
       for ( ; ptr ; ptr= static_cast<RPL_TABLE_LIST*>(ptr->next_global))
       {
-        if (ptr->m_tabledef.compatible_with(rli, ptr->table))
+        TABLE *conv_table;
+        if (!ptr->m_tabledef.compatible_with(thd, const_cast<Relay_log_info*>(rli),
+                                             ptr->table, &conv_table))
         {
+          DBUG_PRINT("debug", ("Table: %s.%s is not compatible with master",
+                               ptr->table->s->db.str,
+                               ptr->table->s->table_name.str));
           mysql_unlock_tables(thd, thd->lock);
           thd->lock= 0;
           thd->is_slave_error= 1;
           const_cast<Relay_log_info*>(rli)->clear_tables_to_lock();
           DBUG_RETURN(Old_rows_log_event::ERR_BAD_TABLE_DEF);
         }
+        DBUG_PRINT("debug", ("Table: %s.%s is compatible with master"
+                             " - conv_table: %p",
+                             ptr->table->s->db.str,
+                             ptr->table->s->table_name.str, conv_table));
+        ptr->m_conv_table= conv_table;
       }
     }
 
@@ -1578,7 +1588,9 @@ int Old_rows_log_event::do_apply_event(Relay_log_info const *rli)
       RPL_TABLE_LIST *ptr= rli->tables_to_lock;
       for ( ; ptr ; ptr= static_cast<RPL_TABLE_LIST*>(ptr->next_global))
       {
-        if (ptr->m_tabledef.compatible_with(rli, ptr->table))
+        TABLE *conv_table;
+        if (ptr->m_tabledef.compatible_with(thd, const_cast<Relay_log_info*>(rli),
+                                            ptr->table, &conv_table))
         {
           mysql_unlock_tables(thd, thd->lock);
           thd->lock= 0;
@@ -1586,12 +1598,14 @@ int Old_rows_log_event::do_apply_event(Relay_log_info const *rli)
           const_cast<Relay_log_info*>(rli)->clear_tables_to_lock();
           DBUG_RETURN(ERR_BAD_TABLE_DEF);
         }
+        ptr->m_conv_table= conv_table;
       }
     }
 
     /*
-      ... and then we add all the tables to the table map and remove
-      them from tables to lock.
+      ... and then we add all the tables to the table map but keep
+      them in the tables to lock list.
+
 
       We also invalidate the query cache for all the tables, since
       they will now be changed.