fix: CREATE TABLE (col TIMESTAMP(6) DEFAULT NOW(2))

That is, when the precision of DEFAULT NOW() is less than
the precision of the column, do not convert it to unireg_check,
use the new approach where DEFAULT is tryly an expression.

5 files changed, 93 insertions, 70 deletions

diff --git a/mysql-test/r/default.result b/mysql-test/r/default.result
index 1f60e66e64e..62dee045604 100644
--- a/mysql-test/r/default.result
+++ b/mysql-test/r/default.result
@@ -253,7 +253,7 @@ CREATE or replace TABLE t1 (event_time TIMESTAMP(6) NOT NULL DEFAULT CURRENT_TIM
 SHOW CREATE TABLE t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
-  `event_time` timestamp(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(6) ON UPDATE CURRENT_TIMESTAMP(6)
+  `event_time` timestamp(6) NOT NULL DEFAULT CURRENT_TIMESTAMP(2) ON UPDATE CURRENT_TIMESTAMP(6)
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
 CREATE or replace TABLE t1 (event_time TIMESTAMP(6) NOT NULL DEFAULT SYSDATE(2) ON UPDATE CURRENT_TIMESTAMP);
 SHOW CREATE TABLE t1;
diff --git a/mysql-test/r/func_default.result b/mysql-test/r/func_default.result
index aac5f4942a7..535be10da86 100644
--- a/mysql-test/r/func_default.result
+++ b/mysql-test/r/func_default.result
@@ -29,6 +29,6 @@ insert t1 () values ();
 insert t1 (a) values (10);
 select default(a),default(b),default(c),default(d),default(e),default(f) from t1;
 default(a)	default(b)	default(c)	default(d)	default(e)	default(f)
-1	2	foo	bar	2001-01-01 10:20:30	2001-01-01 10:20:30.123456
-1	11	foo	bar	2001-01-01 10:20:30	2001-01-01 10:20:30.123456
+1	2	foo	bar	2001-01-01 10:20:30	2001-01-01 10:20:30.120000
+1	11	foo	bar	2001-01-01 10:20:30	2001-01-01 10:20:30.120000
 drop table t1;
diff --git a/mysql-test/r/type_timestamp_hires.result b/mysql-test/r/type_timestamp_hires.result
index 89f6754ec9a..3b88454ba00 100644
--- a/mysql-test/r/type_timestamp_hires.result
+++ b/mysql-test/r/type_timestamp_hires.result
@@ -272,33 +272,64 @@ select * from t1;
 a
 2011-01-01 01:01:01.12345
 drop table t1;
-create table t1 (a timestamp(5) default current_timestamp);
+create or replace table t1 (a timestamp(5) default current_timestamp);
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `a` timestamp(5) NOT NULL DEFAULT CURRENT_TIMESTAMP(5)
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
-drop table t1;
-create table t1 (a timestamp(5) default current_timestamp());
-drop table t1;
-create table t1 (a timestamp(5) default current_timestamp(2));
+create or replace table t1 (a timestamp(5) default current_timestamp());
 show create table t1;
 Table	Create Table
 t1	CREATE TABLE `t1` (
   `a` timestamp(5) NOT NULL DEFAULT CURRENT_TIMESTAMP(5)
 ) ENGINE=MyISAM DEFAULT CHARSET=latin1
-drop table t1;
-create table t1 (a timestamp(5) default current_timestamp(5));
-drop table t1;
-create table t1 (a timestamp(5) default current_timestamp(6));
-drop table t1;
-create table t1 (a timestamp(5) on update current_timestamp);
-drop table t1;
-create table t1 (a timestamp(5) on update current_timestamp());
-drop table t1;
-create table t1 (a timestamp(5) on update current_timestamp(3));
+create or replace table t1 (a timestamp(5) default current_timestamp(2));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` timestamp(5) NOT NULL DEFAULT current_timestamp(2)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+insert t1 () values ();
+select * from t1;
+a
+2011-01-01 01:01:01.12000
+create or replace table t1 (a timestamp(5) default current_timestamp(5));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` timestamp(5) NOT NULL DEFAULT CURRENT_TIMESTAMP(5)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create or replace table t1 (a timestamp(5) default current_timestamp(6));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` timestamp(5) NOT NULL DEFAULT CURRENT_TIMESTAMP(5)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create or replace table t1 (a timestamp(5) on update current_timestamp);
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` timestamp(5) NOT NULL DEFAULT '0000-00-00 00:00:00.00000' ON UPDATE CURRENT_TIMESTAMP(5)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create or replace table t1 (a timestamp(5) on update current_timestamp());
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` timestamp(5) NOT NULL DEFAULT '0000-00-00 00:00:00.00000' ON UPDATE CURRENT_TIMESTAMP(5)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create or replace table t1 (a timestamp(5) on update current_timestamp(3));
 ERROR HY000: Invalid ON UPDATE clause for 'a' column
-create table t1 (a timestamp(5) on update current_timestamp(5));
-drop table t1;
-create table t1 (a timestamp(5) on update current_timestamp(6));
+create or replace table t1 (a timestamp(5) on update current_timestamp(5));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` timestamp(5) NOT NULL DEFAULT '0000-00-00 00:00:00.00000' ON UPDATE CURRENT_TIMESTAMP(5)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
+create or replace table t1 (a timestamp(5) on update current_timestamp(6));
+show create table t1;
+Table	Create Table
+t1	CREATE TABLE `t1` (
+  `a` timestamp(5) NOT NULL DEFAULT '0000-00-00 00:00:00.00000' ON UPDATE CURRENT_TIMESTAMP(5)
+) ENGINE=MyISAM DEFAULT CHARSET=latin1
 drop table t1;
diff --git a/mysql-test/t/type_timestamp_hires.test b/mysql-test/t/type_timestamp_hires.test
index c51fb2fb247..0b05f81ef42 100644
--- a/mysql-test/t/type_timestamp_hires.test
+++ b/mysql-test/t/type_timestamp_hires.test
@@ -17,18 +17,26 @@ drop table t1;
 #
 # MDEV-438 Microseconds: Precision is ignored in CURRENT_TIMESTAMP(N) when it is given as a default column value 
 #
-create table t1 (a timestamp(5) default current_timestamp);
+create or replace table t1 (a timestamp(5) default current_timestamp);
 show create table t1;
-drop table t1;
-create table t1 (a timestamp(5) default current_timestamp()); drop table t1;
-create table t1 (a timestamp(5) default current_timestamp(2));
+create or replace table t1 (a timestamp(5) default current_timestamp());
+show create table t1;
+create or replace table t1 (a timestamp(5) default current_timestamp(2));
+show create table t1;
+insert t1 () values ();
+select * from t1;
+create or replace table t1 (a timestamp(5) default current_timestamp(5));
+show create table t1;
+create or replace table t1 (a timestamp(5) default current_timestamp(6));
+show create table t1;
+create or replace table t1 (a timestamp(5) on update current_timestamp);
+show create table t1;
+create or replace table t1 (a timestamp(5) on update current_timestamp());
 show create table t1;
-drop table t1;
-create table t1 (a timestamp(5) default current_timestamp(5)); drop table t1;
-create table t1 (a timestamp(5) default current_timestamp(6)); drop table t1;
-create table t1 (a timestamp(5) on update current_timestamp); drop table t1;
-create table t1 (a timestamp(5) on update current_timestamp()); drop table t1;
 --error ER_INVALID_ON_UPDATE
-create table t1 (a timestamp(5) on update current_timestamp(3));
-create table t1 (a timestamp(5) on update current_timestamp(5)); drop table t1;
-create table t1 (a timestamp(5) on update current_timestamp(6)); drop table t1;
+create or replace table t1 (a timestamp(5) on update current_timestamp(3));
+create or replace table t1 (a timestamp(5) on update current_timestamp(5));
+show create table t1;
+create or replace table t1 (a timestamp(5) on update current_timestamp(6));
+show create table t1;
+drop table t1;
diff --git a/sql/field.cc b/sql/field.cc
index b8816c59d9f..73e6b4edc3c 100644
--- a/sql/field.cc
+++ b/sql/field.cc
@@ -9863,59 +9863,43 @@ bool Column_definition::check(THD *thd)
       }
     }
   }
+
   if (default_value && (flags & AUTO_INCREMENT_FLAG))
   {
     my_error(ER_INVALID_DEFAULT, MYF(0), field_name);
     DBUG_RETURN(1);
   }
 
-  if (default_value && !default_value->expr_item->basic_const_item())
+  if (default_value && !default_value->expr_item->basic_const_item() &&
+      mysql_type_to_time_type(sql_type) == MYSQL_TIMESTAMP_DATETIME &&
+      default_value->expr_item->type() == Item::FUNC_ITEM)
   {
-    Item *def_expr= default_value->expr_item;
-
-    unireg_check= Field::NONE;
     /*
-      NOW() for TIMESTAMP and DATETIME fields are handled as in MariaDB 10.1
-      by marking them in unireg_check.
+      Special case: NOW() for TIMESTAMP and DATETIME fields are handled
+      as in MariaDB 10.1 by marking them in unireg_check.
     */
-    if (def_expr->type() == Item::FUNC_ITEM &&
-        (static_cast<Item_func*>(def_expr)->functype() ==
-         Item_func::NOW_FUNC &&
-         (mysql_type_to_time_type(sql_type) == MYSQL_TIMESTAMP_DATETIME)))
+    Item_func *fn= static_cast<Item_func*>(default_value->expr_item);
+    if (fn->functype() == Item_func::NOW_FUNC &&
+        (fn->decimals == 0 || fn->decimals >= length))
     {
-      /*
-        We are not checking the number of decimals for timestamps
-        to allow one to write (for historical reasons)
-        TIMESTAMP(6) NOT NULL DEFAULT CURRENT_TIMESTAMP
-        Instead we are going to use the number of decimals specifed by the
-        column.
-      */
       default_value= 0;
-      unireg_check= (on_update ?
-                     Field::TIMESTAMP_DNUN_FIELD : // for insertions and for updates.
-                     Field::TIMESTAMP_DN_FIELD);   // only for insertions.
+      unireg_check= Field::TIMESTAMP_DN_FIELD;
     }
-    else if (on_update)
-      unireg_check= Field::TIMESTAMP_UN_FIELD; // function default for updates
-  }
-  else
-  {
-    /* No function default for insertions. Either NULL or a constant. */
-    if (on_update)
-      unireg_check= Field::TIMESTAMP_UN_FIELD; // function default for updates
-    else
-      unireg_check= ((flags & AUTO_INCREMENT_FLAG) ?
-                     Field::NEXT_NUMBER : // Automatic increment.
-                     Field::NONE);
   }
 
-  if (on_update &&
-      (mysql_type_to_time_type(sql_type) != MYSQL_TIMESTAMP_DATETIME ||
-       on_update->decimals < length))
+  if (on_update)
   {
-    my_error(ER_INVALID_ON_UPDATE, MYF(0), field_name);
-    DBUG_RETURN(TRUE);
+    if (mysql_type_to_time_type(sql_type) != MYSQL_TIMESTAMP_DATETIME ||
+        on_update->decimals < length)
+    {
+      my_error(ER_INVALID_ON_UPDATE, MYF(0), field_name);
+      DBUG_RETURN(TRUE);
+    }
+    unireg_check= unireg_check == Field::NONE ? Field::TIMESTAMP_UN_FIELD
+                                              : Field::TIMESTAMP_DNUN_FIELD;
   }
+  else if (flags & AUTO_INCREMENT_FLAG)
+    unireg_check= Field::NEXT_NUMBER;
 
   sign_len= flags & UNSIGNED_FLAG ? 0 : 1;