MDEV-19632 Replication aborts with ER_SLAVE_CONVERSION_FAILED upon CREATE ... SELECT in ORACLE mode

- Adding optional qualifiers to data types:
    CREATE TABLE t1 (a schema.DATE);
  Qualifiers now work only for three pre-defined schemas:

    mariadb_schema
    oracle_schema
    maxdb_schema

  These schemas are virtual (hard-coded) for now, but may turn into real
  databases on disk in the future.

- mariadb_schema.TYPE now always resolves to a true MariaDB data
  type TYPE without sql_mode specific translations.

- oracle_schema.DATE translates to MariaDB DATETIME.

- maxdb_schema.TIMESTAMP translates to MariaDB DATETIME.

- Fixing SHOW CREATE TABLE to use a qualifier for a data type TYPE
  if the current sql_mode translates TYPE to something else.

The above changes fix the reported problem, so this script:

    SET sql_mode=ORACLE;
    CREATE TABLE t2 AS SELECT mariadb_date_column FROM t1;

is now replicated as:

    SET sql_mode=ORACLE;
    CREATE TABLE t2 (mariadb_date_column mariadb_schema.DATE);

and the slave can unambiguously treat DATE as the true MariaDB DATE
without ORACLE specific translation to DATETIME.

Similar,

    SET sql_mode=MAXDB;
    CREATE TABLE t2 AS SELECT mariadb_timestamp_column FROM t1;

is now replicated as:

    SET sql_mode=MAXDB;
    CREATE TABLE t2 (mariadb_timestamp_column mariadb_schema.TIMESTAMP);

so the slave treats TIMESTAMP as the true MariaDB TIMESTAMP
without MAXDB specific translation to DATETIME.

1 files changed, 4 insertions, 0 deletions

diff --git a/sql/structs.h b/sql/structs.h
index 12bd568d7c5..351847d00ec 100644
--- a/sql/structs.h
+++ b/sql/structs.h
@@ -610,6 +610,10 @@ public:
   {
     set(handler, 0, 0);
   }
+  void set_handler(const Type_handler *handler)
+  {
+    m_handler= handler;
+  }
   const Type_handler *type_handler() const { return m_handler; }
 };