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, 13 insertions, 0 deletions

diff --git a/sql/field.cc b/sql/field.cc
index f5daab00670..e011e01dce7 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -10407,6 +10407,19 @@ void Column_definition::set_attributes(const Lex_field_type_st &type,
   set_handler(type.type_handler());
   charset= cs;
 
+#if MYSQL_VERSION_ID > 100500
+#error When merging to 10.5, please move the code below to
+#error Type_handler_timestamp_common::Column_definition_set_attributes()
+#else
+  /*
+    Unlike other types TIMESTAMP fields are NOT NULL by default.
+    Unless --explicit-defaults-for-timestamp is given.
+  */
+  if (!opt_explicit_defaults_for_timestamp &&
+      type.type_handler()->field_type() == MYSQL_TYPE_TIMESTAMP)
+    flags|= NOT_NULL_FLAG;
+#endif
+
   if (type.length())
   {
     int err;