MDEV-13358: FIRST_V throw SQL Fehler (1292): Incorrect datetime value

This is backport of 25ad623d64e for 10.2.

The issue is similar to the one from MDEV-13240. Item::save_in_field()
returns an error during tmp table population in a create table from select query
as we try to save an empty string as a date value when
force_return_blank is set to true for window functions.

    MDEV-13240 Wrong warning with MAX(datetime_field) OVER (...)

    The problem resided in Item_window_func implementation,
    and it was revealed by bb-10.2-ext specific changes:

    Item_window_func::save_in_field() works differently in bb-10.2-ext vs 10.2:

    - 10.2 goes through val_str()
    - bb-10.2-ext goes through get_date(), due to Type_handler related changes.
      get_date() tries to convert empty string to DATETIME, hence the warning.

    During a discussion with Vicentiu, it was decided to fix
    Item_window_func::val_xxx() to return NULL
    (instead of an "empty" value, such as 0 for numbers and '' for strings)
    when force_return_blank is set.

1 files changed, 28 insertions, 0 deletions

diff --git a/mysql-test/t/win.test b/mysql-test/t/win.test
index 3dedc1227fd..83427e4edf8 100644
--- a/mysql-test/t/win.test
+++ b/mysql-test/t/win.test
@@ -1965,3 +1965,31 @@ INSERT INTO t1 VALUES (1),(2);
 SELECT i AS fld FROM t1 UNION SELECT COUNT(*) AS fld FROM t1;
 DROP TABLE t1;
 
+--echo #
+--echo # MDEV-13240 Wrong warning with MAX(datetime_field) OVER (...)
+--echo #
+
+CREATE TABLE t1 (dt DATETIME);
+INSERT INTO t1 VALUES ('2017-05-17');
+SELECT MAX(dt) OVER (ORDER BY dt ROWS BETWEEN 1 FOLLOWING AND 1 FOLLOWING) FROM t1;
+DROP TABLE t1;
+
+--echo #
+--echo # MDEV-13358 FIRST_VALUE throws SQL Error (1292): Incorrect datetime value
+--echo #
+CREATE TABLE IF NOT EXISTS `fv_test` (
+        `SOME_DATE` datetime NOT NULL
+        );
+
+INSERT INTO `fv_test` (`SOME_DATE`) VALUES ('2017-07-20 12:47:56');
+
+CREATE TABLE fv_result
+SELECT
+FIRST_VALUE(SOME_DATE) OVER(ORDER BY SOME_DATE DESC) AS somedate
+FROM fv_test;
+
+SHOW CREATE TABLE fv_result;
+
+SELECT * FROM fv_result;
+
+DROP TABLE fv_test, fv_result;