"AS OF" clean in Type_handler

This patch does the following:

1. Makes Field_vers_trx_id::type_handler() return
  &type_handler_vers_trx_id rather than &type_handler_longlong.
  Fixes Item_func::convert_const_compared_to_int_field() to
  test field_item->type_handler() against &type_handler_vers_trx_id,
  instead of testing field_item->vers_trx_id().

2. Removes VERS_TRX_ID related code from
  Type_handler_hybrid_field_type::aggregate_for_comparison(),
  because "BIGINT UNSIGNED GENERATED ALWAYS AS ROW {START|END}"
  columns behave just like a BIGINT in a regular comparison,
  i.e. when not inside AS OF.

3. Removes
   - Type_handler_hybrid_field_type::m_vers_trx_id;
   - Type_handler_hybrid_field_type::m_flags;
  because a "BIGINT UNSIGNED GENERATED ALWAYS AS ROW {START|END}"
  behaves like a regular BIGINT column when in UNION.

4. Removes Field::vers_trx_id(), Item::vers_trx_id(), Item::field_flags()
  They are not needed anymore. See N1.

1 files changed, 1 insertions, 11 deletions

diff --git a/sql/field.h b/sql/field.h
index ed8a11806da..6fb5c0c0f37 100644
--- a/sql/field.h
+++ b/sql/field.h
@@ -1461,11 +1461,6 @@ public:
     return flags & VERS_UPDATE_UNVERSIONED_FLAG;
   }
 
-  virtual bool vers_trx_id() const
-  {
-    return false;
-  }
-
   /*
     Validate a non-null field value stored in the given record
     according to the current thread settings, e.g. sql_mode.
@@ -2313,8 +2308,7 @@ public:
                        unsigned_arg),
         cached(0)
   {}
-  enum_field_types real_type() const { return MYSQL_TYPE_LONGLONG; }
-  enum_field_types type() const { return MYSQL_TYPE_LONGLONG;}
+  const Type_handler *type_handler() const { return &type_handler_vers_trx_id; }
   uint size_of() const { return sizeof(*this); }
   bool get_date(MYSQL_TIME *ltime, ulonglong fuzzydate, ulonglong trx_id);
   bool get_date(MYSQL_TIME *ltime, ulonglong fuzzydate)
@@ -2341,10 +2335,6 @@ public:
   }
   /* cmp_type() cannot be TIME_RESULT, because we want to compare this field against
      integers. But in all other cases we treat it as TIME_RESULT! */
-  bool vers_trx_id() const
-  {
-    return true;
-  }
 };